A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice (part 6 of 13)

A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice (part 6 of 13)

1. The Barrel. Its interior is called the bore; its diameter, the calibre; the back end, the breech; the front end, the muzzle; and the closing of the back end, the breech pin or plug. The barrel is generally made of iron. Most military musquets and low-priced guns are fashioned out of a long slip of sheet-iron folded together edge-wise round a skewer into a cylinder, are then lapped over at the seam, and welded at a white heat. The most ductile and tenacious soft iron, free from all blemishes, must be selected for this slip. It is frequently welded at the common forge, but a proper air-furnace answers better, not being so apt to burn it. It should be covered with ashes or cinders. The shape of the bore is given by hammering the cylinder upon a steel mandril, in a groove of the anvil. Six inches of the barrel at either end are left open for forming the breech and the muzzle by a subsequent welding operation; the extremity put into the fire being stopped with clay, to prevent the introduction of cinders. For every length of two inches, there are from two to three welding operations, divided into alternating high and low heats; the latter being intended to correct the defects of the former. The breech and muzzle are not welded upon the mandril, but upon the horn of the anvil; the breech being thicker in the metal, is more highly heated, and is made somewhat wider to save labour to the borer. The barrel is finally hammered in the groove of the anvil without the mandril, during which process it receives a heat every two minutes. In welding, the barrel extends about one-third in length; and for musquets, is eventually left from 3 to 3-1/2 feet long; but for cavalry pistols, only 9 inches.

The best iron plates for gun-barrels are those made of stub iron, that is of old horse-shoe nails welded together, and forged into thin bars, or rather narrow ribands. At one time damascus barrels were much in vogue; they were fashioned either as above described, from plates made of bars of iron and steel laid parallel, and welded together, or from ribands of the same damascus stuff coiled into a cylinder at a red heat, and then welded together at the seams. The best modern barrels for fowling pieces are constructed of stub-nail iron in this manner. The slip or fillet is only half an inch broad or sometimes less, and is left thicker at the end which is to form the breech, and thinner at the end which is to form the muzzle, than in the intermediate portion. This fillet being moderately heated to increase its pliancy, is then lapped round the mandril in a spiral direction till a proper length of cylinder is formed; the edges being made to overlap a little in order to give them a better hold in the welding process. The coil being taken off the mandril and again heated, is struck down vertically with its muzzle end upon the anvil, whereby the spiral junctions are made closer and more uniform. It is now welded at several successive heats, hammered by horizontal strokes, called jumping, and brought into proper shape on the mandril. The finer barrels are made of still narrower, stub-iron slips, whence they get the name of wire twist. On the Continent, barrels are made of steel wire, welded together lengthwise, then coiled spirally into a cylinder. Barrels that are to be rifled, require to be made of thicker iron, and that of the very best quality, for they would be spoiled by the least portion of scale upon their inside. Soldiers’ musquets are thickened a little at the muzzle, to give a stout holding to the bayonet.

The barrels thus made are annealed with a gentle heat in a proper furnace, and slowly cooled. They are now ready for the borer, which is an oblong square bit of steel, pressed in its rotation against the barrel, by a slip of wood applied to one of its flat sides, and held in its place by a ring of metal. The boring bench works horizontally, and has a very shaky appearance, in respect at least of the bit. In some cases, however, it has been attempted to work the barrels and bits at an inclination to the horizon of 30°, in order to facilitate the discharge of the borings. The barrel is held in a slot by only one point, to allow it to humour the movements of the borer, which would otherwise be infallibly broken. The bit, as represented in fig. 395., has merely its square head inserted into a clamp-chuck of the lathe, and plays freely through the rest of its length.

Fig. 396. represents in plan the boring bench for musquet barrels; f f is the sledge or carriage frame in which the barrel is supported; a is the revolving chuck of the lathe, into which the square end of the bit, fig.. 395., is inserted; b is the barrel, clamped at its middle to the carriage, and capable of being pressed onwards against the tapering bit of the borer, by the bent lever c, worked by the left hand of the operative against fulcrum knobs at d, which stand about two inches asunder. Whenever the barrel has been thereby advanced a certain space to the right, the bent end of the lever is shifted against another knob or pin. The borer appears to a stranger to be a very awkward and unsteady mechanism, but its perpetual vibrations do not affect the accuracy of the bore. The opening broach may be of a square or pentagonal form; and either gradually tapered from its thickest part, or of uniform diameter till within two inches of the end, whence it is suddenly tapered to a point.

A series of bits may be used for boring a barrel, beginning with the smallest and ending with the largest. But this multiplication of tools becomes unnecessary, by laying against the cutting part of the bit, slips of wood, called spales, of gradually increasing thickness, so that the edge is pressed by them progressively further from the axis. The bore is next polished. This is done by a bit with a very smooth edge, which is mounted as above, with a wedge of wood besmeared with a mixture of oil and emery. The inside is finished by working a cylindrical steel file quickly backwards and forwards within it, while it is revolving slowly.

In boring, the bit must be well oiled or greased, and the barrel must be kept cool by letting water trickle on it; for the bit, revolving at the rate of 120 or 140 times a minute, generates a great deal of heat. If a flaw be detected in the barrel during the boring, that part is hammered in, and then the bit is employed to turn it out.

Many sportsmen are of opinion that a barrel with a bore somewhat narrowed towards the muzzle serves to keep shot better together; and that roughening its inside with pounded glass has a good effect, with the same view. For this purpose, also, fine spiral lines have been made in their interior surface. The justness of its calibre is tried by means of a truly turned cylinder of steel, 3 or 4 inches long, which ought to move without friction, but with uniform contact from end to end of the barrel. Whatever irregularities appear must be immediately removed.

The outer surface of the barrel is commonly polished upon a dry grindstone, but it is better finished, and less dangerously to the workman, at a turning lathe with a slide rest. If a stone be used, it should be made to revolve at the mouth of a tunnel of some kind, into which there is a good draught to carry off the ferruginous particles. A piece of moist cloth or leather should be suspended before the orifice.

Rifle barrels have parallel grooves of a square or angular form cut within them, each groove being drawn in succession. These grooves run spirally, and form each an aliquot part of a revolution from the chamber to the muzzle. Rifles should not be too deeply indented; only so much as to prevent the ball turning round within the barrel. and the spires should be truly parallel, that the ball may glide along with a regular pace. See infra.

The Parisian gun-makers, who are reckoned very expert, draw out the iron for the barrels at hand forges, in fillets only one-ninth of an inch thick, one inch and a half broad, and four feet long. Twenty-five of these ribands are laid upon each other, between two similar ones of double thickness, and the bundle, weighing 60 pounds, bound with wire at two places, serves to make two barrels. The thicker plates are intended to protect the thinner from the violence of the fire in the numerous successive heats necessary to complete the welding, and to form the bundle into a bar two-thirds of an inch broad, by half an inch thick; the direction of the individual plates relatively to the breadth being preserved. This bar folded flat upon itself, is again wrought at the forge, till it is only half an inch broad, and a quarter of an inch thick, while the plates of the primitive ribands are now set perpendicular to the breadth of the narrow fillet; the length of which must be 15 or 16 feet French (16 or 17 English), to form a fowling piece from 28 to 30 inches long. This fillet, heated to a cherry red in successive portions, is coiled into as close a spiral as possible, upon a mandril about two-fifths of an inch in diameter. The mandril has at one end a stout head for drawing it out, by means of the hammer and the grooves of the anvil, previous to every heating. The welding is performed upon a mandril introduced after each heat; the middle of the barrel being first worked, while the fillets are forced back against each other, along the surface of the mandril, to secure their perfect union. The original plates having in the formation of the ultimate long riband become very thin, appear upon the surface of the barrel like threads of a fine screw, with blackish tints to mark the junctions. In making a double-barrelled gun, the two are formed from the same bundle of slips, the coils of the one finished fillet being turned to the right hand, and those of the other to the left.

The Damascus barrels forged as above described, from a bundle of steel and iron plates laid alternately together, are twisted at the forge several times, then coiled and welded as usual. Fifteen Parisian workmen concur in one operation: six at the forge; two at the boring mill; seven at filing, turning, and adjusting; yet all together make only six pairs of barrels per week, which are sold at from 100 to 300 francs the pair, ready for putting into the stock.

The breeching is of three kinds: the common; the chamber, plug, or mortar, fig. 397.; and the patent, fig. 398. The common was formerly used for soldiers’ musquets and inferior pieces. The second is a trifling improvement upon it. In the patent breeching, the screws do not interfere with the touch-hole, and the ignition is quicker in the main chamber.

The only locks which it is worth while to describe are those upon the percussion principle, as flint locks will certainly soon cease to be employed even in military musquets. Forsyth’s lock (fig. 399.) was an ingenious contrivance. It has a magazine a, for containing the detonating powder, which revolves round a roller b, whose end is screwed into the breech of the barrel. The priming powder passes through a small hole in the roller, which leads to a channel in communication with the chamber of the gun.

The pan for holding the priming is placed immediately over the little hole in the roller. There is a steel punch c, in the magazine, whose under end stands above the pan, ready to ignite the priming when struck upon the top by the cock d, whenever the trigger is drawn. The punch immediately after being driven down into the pan is raised by the action of a spiral spring. For each explosion, the magazine must be turned so far round as to let fall a portion of the percussion powder into the pan; after which it is turned back, and the steel punch recovers its proper position for striking another blow into the pan.

The invention of the copper percussion cap was another great improvement upon the detonating plan. Fig. 400. represents the ordinary percussion lock, which is happily divested of three awkward projections upon the flint lock, namely, the hammer, hammer spring, and the pan. Nothing now appears upon the plate of the lock, but the cock or striking hammer, which inflicts the proper blow upon the percussion cap. It is concave, with a small metallic ring or border, called a shield or fence, for the purpose of enclosing the cap, as it were, and preventing its splinters doing injury to the sportsman, as also protecting against the line of flame which may issue from the touch-hole in the cap nipple. This is screwed into the patent breech, and is perforated with a small hole.

The safety lock of Dr. Somerville is a truly humane invention. Its essential feature is a slide stop or catch, placed under the trigger A, fig. 401. It is pulled forward into a notch in the trigger, by means of a spring B, upon the front of the guard, which is worked by a key C, pressing upon the spring when the piece is discharged. In another safety plan there is a small movable curved piece of iron, A, which rises through an opening B, in the lock-plate C, and prevents the cock from reaching the nipple, as represented in the figure, until it is drawn back within the plate of the lock when the piece is fired.

To fire this gun, two different points must be pressed at the same time. If by accident the key which works the safety be touched, nothing happens, because the trigger is not drawn; and the trigger touched alone can produce no effect, because it is locked. The pressure must be applied to the trigger and the key at the same instant, otherwise the lock will not work.

The French musquet is longer than the British, in the proportion of 44·72 inches to 42; but the French bayonet is 15 inches, whereas the British is 17.

Eng. Fr. Dimensions. Dimensions. Diameter of the bore 0·75 in. 0·69 in. Diameter of the ball 0·676 0·65 Weight of the ball in oz. 1·06 0·958 Weight of the firelock and bayonet in libs. 12·25 10·980 Length of the barrel and bayonet 59·00 59·72

Within these few years a great many contrivances have been brought forward, and several have been patented for fire arms. The first I shall notice is that of Charles Random, Baron de Berenger. Fig. 402. shows the lock and breech of a fowling piece, with a sliding protector on one of the improved plans; a is the hammer, b the nipple of the touch-hole, c a bent lever, turning upon a pin, fixed into the lock-plate at d. The upper end of this bent lever stands partly under the nose of the hammer, and while in that situation stops it from striking the nipple. A slider g f h, connected with the under part of the gun-stock, is attached to the tail of the bent lever at i; and when the piece is brought to the shoulder for firing, the hand of the sportsman pressing against the bent part of the slider at g, forces this back, and thereby moves the end of the lever c forwards from under the nose of the cock or hammer, as shown by the dotted lines. The trigger being now drawn, the piece will be discharged; and on removing the hand from the end g, of the slider f, the spring at h acting against the guard, will force the slider forward, and the lever into the position first described.

Mr. Redford, gun-maker of Birmingham, proposes a modification of the lock for small fire-arms, in which the application of pressure to the sear spring for discharging the piece is made by means of a plug, depressed by the thumb, instead of the force of the finger exerted against the trigger. Fig. 403. represents a fowling piece partly in section. The sear spring is shown at a. It is not here connected with the trigger as in other locks; but is attached by a double-jointed piece to a lever b, which turns upon a fulcrum pin in its centre. At the reverse end of this lever an arm extends forwards, like that of an ordinary sear spring, upon which arm the lower end of the plug c is intended to bear; and when this plug is depressed by the thumb bearing upon it, that end of the lever b will be forced downwards, and the reverse end will be raised, so as to draw up the end of the sear spring, and set off the piece. For the sake of protection, the head of the plug c is covered by a movable cap d, forming part of a slider e, which moves to and fro in a groove in the stock, behind the breech end of the barrel; this slider e is acted upon by the trigger through levers, which might be attached to the other side of the lock-plate; but are not shown in this figure to avoid confusion. When the piece is brought to the shoulder for firing, the fore-finger must be applied as usual to the trigger, but merely for the purpose of drawing back the slider e, and uncovering the head of the plug; when this is done, the thumb is to be pressed upon the head of the plug, and will thus discharge the piece. A spring bearing against the lever of the slider e, will, when the finger is withdrawn from the trigger, send the slider forward again, and cover the head of the plug, as shown.

It is with pleasure I again advert to the humane ingenuity of the Rev. John Somerville, of Currie. In April, 1835, he obtained a patent for a further invention to prevent the accidental discharge of fire arms. It consists in hindering the hammer from reaching the nipple of a percussion lock, or the flint reaching the steel of an ordinary one, by the interposition of movable safety studs or pins, which protrude from under the false breech before the hammers of the locks, and prevent them from descending to strike. These safety studs or pins are moved out of the way by the pressure of the right hand of the person using the gun only when in the act of firing, that is, when the force of the right hand and arm is exerted to press the butt end of the stock of the gun against the shoulder while the aim is taken and the trigger pulled. In carrying the gun at rest, the proper parts of the thumb or hand do not come over Mr. Somerville’s movable buttons or studs.

Fig. 404. is a side view of part of a double percussion gun; and fig. 405. is a top or plan view, which will serve to explain these improvements, and show one, out of many, methods of carrying them into effect. A is the stock of the gun; B the barrels; C the breech; D the nipples; E the false breech, on the under side of which the levers which work the safety studs or pins are placed; F is the shield of the false breech; G, triggers; H the lock-plate; and I the hammers: all of which are constructed as usual: a a are the safety studs or pins, which protrude before the shield F, and work through guide pieces on the under side of the false breech. The button piece is placed in the position for the thumb of the right hand to act upon it; but when the pressure of the ball of the right thumb is to produce the movement of the safety studs, it must be placed in or near the position K; and when the heel of the right hand is to effect the movements of the safety studs, the button piece must be placed at L, or nearly so.

In these last two positions, the lever (which is acted upon by the button piece to work the safety studs through a slide) would require to be of a different shape and differently mounted. When the hammers are down upon the nipples after discharging the gun, the ends of the safety pins press against the inner sides of the hammers. When this invention is adapted to single-barrelled guns, only one pin, a, one lever and button piece will be required.

Mr. Richards, gun-maker, Birmingham, patented, in March, 1836, a modification of the copper cap for holding the percussion powder, as represented fig. 406.; in which the powder is removed from the top of the cap, and brought nearer the mouth; a being the top, b the sides, and c the position of the priming. The dotted lines show the direction of the explosion, whereby it is seen that the metal case is opened or distended only in a small degree, and not likely to burst to pieces, as in the common caps, the space between a and c being occupied by a piece of any kind of hard metal d, soldered or otherwise fastened in the cap.

George Lovell, Esq., director of the Royal Manufactory of Arms at Enfield, has recently made a great improvement upon the priming chamber. He forms it into a vertical double cone, joined in the middle by the common apex; the base of the upper cone being in contact with the percussion cap, presents the most extensive surface to the fulminate upon the one hand, while the base of the under one being in a line with the interior surface of the barrel, presents the largest surface to the gunpowder charge, upon the other. In the old nipple the apex of the cone being at its top, afforded very injudiciously the minimum surface to the exploding force.

Guns, Rifling of the Barrels.--The outside of rifle barrels is, in general, octagonal. After the barrel is bored, and rendered truly cylindrical, it is fixed upon the rifling machine. This instrument is formed upon a square plank of wood 7 feet long, to which is fitted a tube about an inch in diameter, with spiral grooves deeply cut internally through its whole length; and to this a circular plate is attached, about 5 inches diameter, accurately divided in concentric circles, into from 5 to 16 equal parts, and supported by two rings made fast to the plank, in which rings it revolves. An arm connected with the dividing graduated plate, and pierced with holes, through which a pin is passed, regulates the change of the tube in giving the desired number of grooves to the barrel. An iron rod, with a movable handle at the one end, and a steel cutter in the other, passes through the above rifling tube. This rod is covered with a core of lead one foot long. The barrel is firmly fixed by two rings on the plank, standing in a straight line on the tube. The rod is now drawn repeatedly through the barrel, from end to end, until the cutter has formed one groove of the proper depth. The pin is then shifted to another hole in the dividing plate, and the operation of grooving is repeated till the whole number of riflings is completed. The barrel is next taken out of the machine, and finished. This is done by casting upon the end of a small iron rod a core of lead, which, when besmeared with a mixture of fine emery and oil, is drawn, for a considerable time, by the workmen, from the one end of the barrel to the other, till the inner surface has become finely polished. The best degree of spirality is found to be from a quarter to half a revolution in a length of three feet.

Military Rifles.--An essential improvement in this destructive arm has lately been introduced into the British service, at the suggestion of Mr. Lovell:

The intention in all rifles is to impart to the ball a rotatory or spinning motion round its axis, as it passes out through the barrel. This object was attained, to a certain degree, in the rifles of the old pattern, by cutting seven spiral grooves into the inside of the barrel, in the manner shewn by fig. 407., the spherical ball, fig. 408., being a little larger than the bore, was driven down with a mallet, by which the projecting ribs were forced into the surface of the ball, so as to keep it in contact with their curvatures, during its expulsion. Instead of this laborious and insecure process, the barrel being now cut with only two opposite grooves, fig. 409., and the ball being formed with a projecting belt, or zone, round its equator, of the same form as the two grooves, fig. 410., it enters so readily into these hollows, that little or no force is required to press it down upon the powder. So much more hold of the barrel is at the same time obtained, that instead of one quarter of a turn, which was the utmost that could be safely given in the old way, without danger of stripping the ball, a whole turn round the barrel, in its length, can be given to the two grooved rifles; whereby a far more certain and complete rotatory motion is imparted to the ball. The grand practical result is, that better practice has been performed by several companies of the Rifle Corps, at 300 yards, than could be produced with the best old military rifles at 150 yards; the soldier being meanwhile enabled to load with much greater ease and despatch. The belt is bevelled to its middle line, and not so flat as shown in the figure.

This mode of rifling is not, however, new in England. In fact, it is one of the oldest upon record; and appears to have fallen into disuse from faults in the execution. The idea was revived within the last few years in Brunswick, and it was tried in Hanover also, but with a lens-shaped (Linsenförmig) ball. The judicious modifications and improvements it has finally received in Mr. Lovell’s hands, have brought out all its advantages, and rendered it, when skilfully used, a weapon of unerring aim, even at the prodigious distance of 700 yards.

The locks, also, for the military service generally, are now receiving an important improvement by means of his labours, having been simplified in a remarkable manner. The action of the main spring is reversed, as shown by fig. 411.; thus rendering the whole mechanism more solid, compact, and convenient; while the ignition of the charge being effected by percussion powders in a copper cap, the fire of the British line will, in future, be more murderous than ever, as a mis-fire is hardly ever experienced with the fire-arms made at the Royal manufactory, under Mr. Lovell’s skilful superintendence.

FIRE-DAMP; the explosive carburetted hydrogen of coal mines. See PITCOAL.

FIRE-WORKS. (Feux d’artifice, Fr.; Feuerwerke, Germ.) The composition of luminous devices with explosive combustibles, is a modern art resulting from the discovery of gunpowder. The finest inventions of this kind are due to the celebrated Ruggieri, father and son, who executed in Rome and Paris, and the principal capitals of Europe, the most brilliant and beautiful fireworks that were ever seen. The following description of their processes will probably prove interesting to many of my readers.

The three prime materials of this art are, nitre, sulphur, and charcoal, along with filings of iron, steel, copper, zinc, and resin, camphor, lycopodium, &c. Gunpowder is used either in grain, half crushed, or finely ground, for different purposes. The longer the iron filings, the brighter red and white sparks they give; those being preferred which are made with a very coarse file, and quite free from rust. Steel filings and cast-iron borings contain carbon, and afford a more brilliant fire, with wavy radiations. Copper filings give a greenish tint to flame; those of zinc, a fine blue colour; the sulphuret of antimony gives a less greenish blue than zinc, but with much smoke; amber affords a yellow fire, as well as colophony, and common salt; but the last must be very dry. Lampblack produces a very red colour with gunpowder, and a pink with nitre in excess. It serves for making golden showers. The yellow sand or glistening mica, communicates to fire-works golden radiations. Verdigris imparts a pale green; sulphate of copper and sal-ammoniac, a palm-tree green. Camphor yields a very white flame and aromatic fumes, which mask the bad smell of other substances. Benzoin and storax are used also on account of their agreeable odour. Lycopodium burns with a rose colour and a magnificent flame; but it is principally employed in theatres to represent lightning, or to charge the torch of a fury.

Fire-works are divided into three classes: 1. those to be set off upon the ground; 2. those which are shot up into the air; and 3. those which act upon or under water.

Composition for jets of fire; the common preparation for rockets not more than 3/4 of an inch in diameter, is: gunpowder, 16 parts; charcoal, 3 parts. For those of larger diameter: gunpowder, 16; steel filings, 4.

Brilliant revolving wheel; for a tube less than 3/4 of an inch: gunpowder, 16; steel filings, 3. When more than 3/4: gunpowder, 16; filings, 4.

Chinese or Jasmine fire; when less than 3/4 of an inch: gunpowder, 16; nitre, 8; charcoal (fine), 3; sulphur, 3; pounded cast-iron borings (small), 10. When wider than 3/4: gunpowder, 16; nitre, 12; charcoal, 3; sulphur, 3; coarse borings, 12.

A fixed brilliant; less than 3/4 in diameter: gunpowder, 16; steel filings, 4; or, gunpowder, 16; and finely pounded borings, 6.

Fixed suns are composed of a certain number of jets of fire distributed circularly, like the spokes of a wheel. All the fusees take fire at once through channels charged with quick matches. Glories are large suns with several rows of fusees. Fans are portions of a sun, being sectors of a circle. The Patte d’oie is a fan with only three jets.

The mosaic represents a surface covered with diamond shaped compartments, formed by two series of parallel lines crossing each other. This effect is produced by placing at each point of intersection, four jets of fire, which run into the adjoining ones. The intervals between the jets must be associated with the discharge of others, so as to keep up a succession of fires in the spaces.

Palm trees. Ruggieri contrived a new kind of fire, adapted to represent all sorts of trees, and especially the palm. The following is the composition of this magnificent green fire-work: crystallized verdigris, 4 parts; sulphate of copper, 2; sal-ammoniac, 1. These ingredients are to be ground and moistened with alcohol. An artificial tree of any kind being erected, coarse cotton rovings about 2 inches in diameter, impregnated with that composition, are to be festooned round the trunk, branches, and among the leaves; and immediately kindled before the spirits have had time to evaporate.

Cascades, imitate sheets or jets of water. The Chinese fire is best adapted to such decorations.

Fixed stars. The bottom of a rocket is to be stuffed with clay, and one diameter in height of the first preparation being introduced, the vacant space is to be filled with the following composition, and the mouth tied up. The pasteboard must be pierced into the preparation, with five holes, for the escape of the luminous rays, which represent a star.

Composition of fixed stars:--

Ordinary. Brighter. Coloured. Nitre, 16 12 0 Sulphur, 4 6 6 Gunpowder meal, 4 12 16 Antimony, 2 1 2

Lances, are long rockets of small diameter, made with cartridge paper. Those which burn quickest should be the longest. They are charged by hand without any mould, with rods of different lengths, and are not strangled at the mouth, but merely stuffed with a quick match of tow. These lances form the figures of great decorations; they are fixed with sprigs upon large wooden frame works, representing temples, palaces, pagodas, &c. The whole are placed in communication by conduits, or small paper cartridges like the lances, but somewhat conical, that they may fit endwise into one another to any extent that may be desired. Each is furnished with a match thread fully 1-1/2 inches long, at its two ends.

Composition for the white lances: nitre, 16; sulphur, 8; gunpowder, 4 or 3. For a bluish-white: nitre, 16; sulphur, 8; antimony, 4. For blue lances: nitre, 16; antimony, 8. For yellow: nitre, 16; gunpowder, 16; sulphur, 8; amber, 8. For yellower ones: nitre, 16; gunpowder, 16; sulphur, 4; colophony, 3; amber, 4. For greenish ones: nitre, 16; sulphur, 6; antimony, 6; verdigris, 6. For pink lances; nitre, 16; gunpowder, 3; lampblack, 1. Others less vivid are made with: nitre, 16; colophony, 3; amber, 3; lycopodium, 3.

Cordage is represented in fire-works, by imbuing soft ropes with a mixture of, nitre, 2; sulphur, 16; antimony, 1; resin of juniper, 1.

The Bengal flames rival the light of day. They consist of, nitre, 7; sulphur, 2; antimony, 1. This mixture is pressed strongly into earthen porringers, with some bits of quick match strewed over the surface. These flames have a fine theatrical effect for conflagrations.

Revolving suns, are wheels upon whose circumference rockets of different styles are fixed, and which communicate by conduits, so that one is lighted up in succession after another. The composition of their common fire is, for sizes below 3/4 of an inch: gunpowder meal, 16; charcoal, not too fine, 3. For larger sizes: gunpowder, 20; charcoal, not too fine, 4. For fiery radiations: gunpowder, 16; yellow micaceous sand, 2 or 3. For mixed radiations: gunpowder, 16; pitcoal, 1; yellow sand, 1 or 2.

The waving or double Catherine wheels, are two suns turning about the same axis in opposite directions. The fusees are fixed obliquely and not tangentially to their peripheries. The wheel spokes are charged with a great number of fusees; two of the four wings revolve in the one direction, and the other two in the opposite; but always in a vertical plane.

The girandoles, caprices, spirals, and some others have on the contrary a horizontal rotation. The fire-worker may diversify their effects greatly by the arrangement and colour of the jets of flame. Let us take for an example the globe of light. Imagine a large sphere turning freely upon its axis, along with a hollow hemisphere, which revolves also upon a vertical axis passing through its under pole. If the two pieces be covered with coloured lances or cordage, a fixed luminous globe will be formed, but if horizontal fusees be added upon the hemisphere, and vertical fusees upon the sphere, the first will have a relative horizontal movement, the second a vertical movement, which being combined with the first, will cause it to describe a species of curve, whose effect will be an agreeable contrast with the regular movement of the hemisphere. Upon the surface of a revolving sun, smaller suns might be placed, to revolve like satellites round their primaries.

Ruggieri exhibited a luminous serpent pursuing with a rapid winding pace, a butterfly which flew continually before it. This extraordinary effect was produced in the following way. Upon the summits of an octagon he fixed eight equal wheels turning freely upon their axles, in the vertical plane of the octagon. An endless chain passed round their circumference, going from the interior to the exterior, covering the outside semi-circumference of the first, the inside of the second, and so in succession; whence arose the appearance of a great festooned circular line. The chain, like that of a watch, carried upon a portion of its length a sort of scales pierced with holes for receiving coloured lances, in order to represent a fiery serpent. At a little distance there was a butterfly constructed with white lances. The piece was kindled commonly by other fireworks, which seemed to end their play, by projecting the serpent from the bosom of the flames. The motion was communicated to the chain by one of the wheels, which received it like a clock from the action of a weight. This remarkably curious mechanism was called by the artists a salamander.

The rockets which rise into the air with a prodigious velocity, are among the most common, but not least interesting fire-works. When employed profusely they form those rich volleys of fire which are the crowning ornaments of a public fête. The cartridge is similar to that of the other jets, except in regard to its length, and the necessity of pasting it strongly, and planing it well; but it is charged in a different manner. As the sky-rockets must fly off with rapidity, their composition should be such as to kindle instantly throughout their length, and extricate a vast volume of elastic fluids. To effect this purpose, a small cylindric space is left vacant round the axis; that is, the central line is tubular. The fire-workers call this space the soul of the rocket (ame de la fusée). On account of its somewhat conical form, hollow rods, adjustable to different sizes of broaches or skewers, are required in packing the charge; which must be done while the cartridge is sustained by its outside mould, or copper cylinder. The composition of sky-rockets is as follows:--

+-------------------------+----------+---------+------+ | When the bore is |3/4 of an | 3/4 to |1-2/3;| | | inch; | 1-1/4; | | +-------------------------+----------+---------+------+ |Nitre |16 |16 | 16 | |Charcoal | 7 | 8 | 9 | |Sulphur | 4 | 4 | 4 | | Brilliant Fire. | | | | |Nitre |16 |16 | 16 | |Charcoal | 6 | 7 | 8 | |Sulphur | 4 | 4 | 4 | |Fine steel filings | 3 | 4 | 5 | | Chinese Fire. | | | | |Nitre |16 |16 | 16 | |Charcoal | 4 | 5 | 6 | |Sulphur | 3 | 3 | 4 | |Fine borings of cast iron| 3 coarser| 4 mixed | 5 | +-------------------------+----------+---------+------+

The cartridge being charged as above described, the pot must be adjusted to it, with the garniture; that is, the serpents, the crackers, the stars, the showers of fire, &c. The pot is a tube of pasteboard wider than the body of the rocket, and about one third of its length. After being strangled at the bottom like the mouth of a phial, it is attached to the end of the fusee by means of twine and paste. These are afterwards covered with paper. The garniture is introduced by the neck, and a paper plug is laid over it. The whole is inclosed within a tube of pasteboard terminating in a cone, which is firmly pasted to the pot. The quick-match is now finally inserted into the soul of the rocket. The rod attached to the end of the sky-rockets to direct their flight, is made of willow or any other light wood. M. Ruggieri replaced the rod by conical wings containing explosive materials, and thereby made them fly further and straighter.

The garnitures of the sky-rocket pots are the following:--

1. Stars are small, round, or cubic solids, made with one of the following compositions, and soaked in spirits. White stars, nitre, 16; sulphur, 8; gunpowder, 3. Others more vivid consist of nitre, 16; sulphur, 7; gunpowder, 4.

Stars for golden showers, nitre, 16; sulphur, 10; charcoal, 4; gunpowder, 16; lamp-black, 2. Others yellower are made with nitre, 16; sulphur, 8; charcoal, 2; lamp-black, 2; gunpowder, 8.

The serpents are small fusees made with one or two playing cards; their bore being less than half an inch. The lardons are a little larger, and have three cards; the vetilles are smaller. Their composition is, nitre, 16; charcoal, not too fine, 2; gunpowder, 4; sulphur, 4; fine steel filings, 6.

The petards are cartridges filled with gunpowder and strangled.

The saxons are cartridges clayed at each end, charged with the brilliant turning fire, and perforated with one or two holes at the extremity of the same diameter.

The cracker is a round or square box of pasteboard, filled with granulated gunpowder, and hooped all round with twine.

Roman candles are fusees which throw out very bright stars in succession. With the composition (as under) imbued with spirits and gum-water, small cylindric masses are made, pierced with a hole in their centre. These bodies, when kindled and projected into the air, form the stars. There is first put into the cartridge a charge of fine gunpowder of the size of the star; above this charge a star is placed; then a charge of composition for the Roman candles.

The stars, when less than 3/4 of an inch, consist of nitre, 16; sulphur, 7; gunpowder, 5. When larger, of nitre, 16; sulphur, 8; gunpowder, 8.

Roman candles, nitre, 16; charcoal, 6; sulphur, 3. When above 3/4 of an inch nitre, 16; charcoal, 8; sulphur, 6.

The girandes, or bouquets, are those beautiful pieces which usually conclude a fire-work exhibition; when a multitude of jets seem to emblazon the sky in every direction, and then fall in golden showers. This effect is produced by distributing a number of cases open at top, each containing 140 sky-rockets, communicating with one another by quick-match strings planted among them. The several cases communicate with each other by conduits, whereby they take fire simultaneously, and produce a volcanic display.

The water fire-works are prepared like the rest; but they must be floated either by wooden bowls, or by discs and hollow cartridges fitted to them.

Blue fire for lances may be made with nitre, 16; antimony, 8; very fine zinc filings, 4. Chinese paste for the stars of Roman candles, bombs, &c.:--Sulphur, 16; nitre, 4; gunpowder meal, 12; camphor, 1; linseed oil, 1; the mixture being moistened with spirits.

The feu grégois of Ruggieri, the son:--Nitre, 4; sulphur, 2; naphtha, 1. See PYROTECHNY and ROCKETS.

The red fire composition is made by mixing 40 parts of nitrate of strontia, 13 of flowers of sulphur, 5 of chlorate of potash, and 4 of sulphuret of antimony.

White fire is produced by igniting a mixture of 48 parts nitre; 13-1/4 sulphur; 7-1/4 sulphuret of antimony; or, 24 nitre, 7 sulphur, 2 realgar; or, 75 nitre, 24 sulphur, 1 charcoal; or, finally, 100 of gunpowder meal, and 25 of cast-iron fine borings.

The blue fire composition is, 4 parts of gunpowder meal; 2 of nitre; sulphur and zinc, each 3 parts.

FISH-HOOKS (Hameçons, Fr.; Fischangeln, Germ.); are constructed with simple tools, but require great manual dexterity in the workmen. The iron wire of which they are made should be of the best quality, smooth, and sound. A bundle of such wire is cut in lengths, either by shears or by laying it down upon an angular wedge of hard steel fixed horizontally in a block or anvil, and striking off the proper lengths by the blows of a hammer. In fashioning the barbs of the hooks, the straight piece of wire is laid down in the groove of an iron block made on purpose, and is dexterously struck by the chisel in a slanting direction, across so much of the wire as may be deemed necessary. A sharp-pointed little wedge is thus formed, whose base graduates into the substance of the metal.

The end of the wire where the line is to be attached is now flattened or screw-tapped; the other end is sharp pointed, and the proper twisted curvature is given. The soft iron hooks are next case-hardened, to give them the steely stiffness and elasticity, by imbedding them in animal charcoal contained in an earthen or iron box; see CASE-HARDENING; after which they are brightened by heating and agitating them with bran, and finally tempered by exposure to a regulated temperature upon a hot iron plate. Hooks for salt-water fishing are frequently tinned, to prevent them wearing rapidly away in rust. See TIN PLATE.

FLAKE WHITE; is the name sometimes given to pure white-lead.

FLAME (Flamme, Fr. and Germ.); is the combustion of an explosive mixture of an inflammable gas or vapour with air. That it is not, as many suppose, combustion merely at the exterior surface, is proved by plunging a fragment of burning phosphorus or sulphur into the centre of a large flame of alcohol. Either of these bodies will continue to burn there with its peculiar light; thus proving that oxygen is mixed with the whole of the burning vapour. If we mix good coal gas with as much atmospheric air as can convert all its carbon into carbonic acid, the mixture will explode with a feeble blue light; but if we mix the same gas with a small quantity of air, it will burn with a rich white flame. In the latter case, the carbonaceous particles are precipitated, as Sir H. Davy first showed, in the interior of the flame, become incandescent, and constitute white light: for from the ignition of solid matter alone can the prismatic rays be emitted in that concentrated union. Towards the interior of the flame of a candle, a lamp, or a gas jet, where the air is scanty, there is a deposition of solid charcoal, which first by its ignition, and afterwards by its combustion, increases in a high degree the intensity of the light. If we hold a piece of fine wire gauze over a jet of coal gas close to the orifice, and if we then kindle the gas, it will burn above the wire with its natural brilliancy; but if we elevate the gauze progressively higher, so as to mix more and more air with it before it reaches the burning point, its flame will become fainter and less white. At a certain distance it becomes blue, like that of the above explosive mixture. Since the combustion of all the constituents is in this case direct and complete, the heat becomes greatest in proportion nearly as the light is diminished. If a few platina wires be held in that dim flame they will grow instantly white hot, and illuminate the apartment. On reversing the order of this experiment, by lowering progressively a flat piece of wire gauze from the summit towards the base of a gas flame, we shall find no charcoal deposited at its top, because plenty of air has been introduced there to convert all the carbon of the gas into carbonic acid, and therefore the apex is blue; but as we descend, more and more charcoal will appear upon the meshes. At the very bottom, indeed, where the atmospheric air impinges upon the gauze, the flame is again blue, and no charcoal can therefore be deposited.

The fact of the increase of the brilliancy and whiteness of flame by the development and ignition of solid matter in its bosom, illustrates many curious phenomena. We can thus explain why olefiant gas affords the most vivid illumination of all the gases; because, being surcharged with charcoal, its hydrogen lets it go in the middle of the flame, as it does in an ignited porcelain tube, whereby its solid particles first get ignited to whiteness, and then burn away. When phosphorus is inflamed, it always yields a pure white light, from the ignition of the solid particles of the snowy acid thus produced.

In the blowpipe, the inner blue flame has the greatest heat, because there the combustion of the whole fatty vapour is complete. The feeble light of burning hydrogen, carbonic oxide, and sulphur, may, upon the principles now expounded, be increased by simply placing in them a few particles of oxide of zinc, slender filaments of amianthus, or fine platina wire. Upwards of twenty years ago, I demonstrated in my public lectures in Glasgow, that by narrowing the top of a long glass chimney over an argand flame either from oil or coal gas, the light could be doubled, at the same cost of material. The very tall chimneys used by the Parisian lampists are very wasteful. I find that with a narrow chimney of half the length of theirs, I can have as good a light, and save 30 per cent. of the oil. Thus the light of a flame may be increased by diminishing its heat, or the intensity of its combustion; and conversely the heat of a flame may be increased by diminishing its light.

FLANNEL; a plain woollen stuff of a rather open and slight fabric.

FLAX. By this term we understand the bast or inner bark of the Linum usitatissimum, which is spun into yarn for weaving linen webs. This plant blossoms in June or July, and commonly ripens its seeds in September. As varieties, we distinguish the spring flax, with short knotty stems, whose seed capsules at the period of maturity, spring open with a perceptible sound; and the close flax, with longer smoother stems, whose capsules give out their seeds only when threshed. The Germans, who have bestowed much attention upon the culture of flax, call the former Klanglein or Springlein, and the latter Dreschlein. This is the kind most commonly grown, but from the difference of climate, soil, and culture, it affords flax of very different qualities. The best ground for this plant is an open, somewhat friable clay, mingled with sand and mould. The early flax is usually sown in the end of April or beginning of May, the late, in June. The seeds ought to be sown thick, whereby the stalks are forced to grow more slender, and the fibres of the bast or harl are not only smoother and finer, but more uniform in length. If the raising of seed be the principal object, the flax must be more thinly sown, whereby it will produce stronger stalks, but more knotty, with shorter fibres, and more productive of tow.

Whenever the flax is ripe, which is shown by the bottom of the stalk becoming yellow, and the leaves beginning to drop off, it must be immediately reaped by pulling it up by the roots. The seeds are still immature, fit merely for the oil press, and not for sowing. When the seed crop is the object, the plant must be suffered to acquire its full maturity; in which case the fibres are less fine and soft.

The flax is carried off the field in bundles to be rippled, or stripped of its seeds, which is done by drawing it by handfuls, through an iron comb with teeth eight inches long, fixed upright in a horizontal beam. When the seeds are more fully ripened, they may be separated by the threshing mill.

The operations next performed upon the flax, will be understood by attending to the structure of the stem. In it, two principal parts are to be distinguished; the woody heart or boon, and the harl (covered outwardly with a fine cuticle), which encloses the former like a tube, consisting of parallel lines. In the natural state, the fibres of the harl are attached firmly not only to the boon, but to each other by means of a green or yellowish substance. The rough stems of the flax after being stripped of their seeds, lose in moisture by drying in warm air, from 55 to 65 per cent. of their weight; but somewhat less when they are quite ripe and woody. In this dry state, they consist in 100 parts of from 20 to 23 per cent. of harl, and from 80 to 77 per cent. of boon. The latter is composed upon the average of 69 per cent. of a peculiar woody substance, 12 per cent. of a matter soluble in water, and 19 per cent. of a body not soluble in water, but in alkaline lyes. The harl contains at a mean 58 per cent. of pure flaxen fibres, 25 parts soluble in water (apparently extractive and albumen), and 17 parts insoluble in water, being chiefly gluten. By treating the harl with either cold or hot water, the latter substance is dyed brown by the soluble matter, while the fibres retain their coherence to one another. Alkaline lyes, and also, though less readily, soap water, dissolve the gluten, which seems to be the cement of the textile fibres, and thus set them free.

The cohesion of the fibres in the rough harl is so considerable that by mechanical means, as by beating, rubbing, &c., a complete separation of them cannot be effected, unless with great loss of time, and rupture of the filaments. This circumstance shows the necessity of having recourse to some chemical method of decomposing the gluten. The process employed with this view is a species of fermentation, to which the flax stalks are exposed; it is called retting, a corruption of rotting, since a certain degree of putrefaction takes place. The German term is rusting. This is the first important step in the preparation of flax. After the retting is completed, the boon of the stalks must be removed by the second operation called breaking, and other subordinate processes. The harl freed from the woody parts contains still a multitude of fibres, more or less coherent, or entangled, and of variable lengths, so as to be ill adapted for spinning. These are removed by the heckle, which separates the connected fibres into their finest filaments, removes those that are too short, and disentangles the longer ones.

I. Of retting.--The fermentation of this process may be either rendered rapid by steeping the flax in water, or slow by using merely the ordinary influence of the atmospheric damp, dews, and rain. Hence the distinction of water-retting and dew-retting. Both may also be combined.

Prior to being retted, the flax should be sorted according to the length and thickness of its stalks, and its state of maturity; the riper the plant, the longer must the retting last. The due length of the process is a point too little studied.

Water-retting.--When flax stalks are macerated in water, at a temperature not too low, fermentation soon begins, evinced in the dingy infusion, by disengagement of carbonic acid gas, and the production of vinegar. If the flax be taken out at the end of a few days, dried, and rubbed, the textile filaments are found to be easily separable from each other. By longer continuance of the steep, the water ceases to be acid, it becomes to a certain degree alkaline, from the production of ammonia, diffuses a fetid odour, from the disengagement of sulphuretted hydrogen gas, along with the carbonic acid; the acetous fermentation being in fact now changed into the putrid. The filaments become yellowish brown, afterwards dark brown and lose much of their tenacity, if the process be carried further.

When the operation is conducted with discernment, the water-retting may be completed by the acetous fermentation alone, as the putrefaction should never be suffered to proceed to any length; because when over-retted, flax is partially rotten, gets a bad colour, and yields a large proportion of tow.

For water-retting, the flax must be bound up in sheaves, placed in layers over each other in the water, or sometimes upright, with the roots undermost. Straw may be put below to keep it from touching the ground, and boards may be laid upon the top, with weights to hold it immersed about a foot beneath the surface, especially when the fermentative gases make it buoyant. As soon as it sinks at the end of the fermentation, it must be inspected at least twice a day, and samples must be taken out to see that no over-retting ensues. A single day too long often injures the flax not a little. We may judge that the retting is sufficient when the harl separates easily from the boon by the fingers, when the boon breaks across without bending, and when several stalks knotted together sink to the bottom upon being thrown into the water. For this completion, a shorter or longer time is required according to the quality of the flax, the temperature, &c., so that the term may vary from five to fourteen days. It may be done either in running or in stagnant water. For the latter purpose, tanks five feet deep are dug in the ground. In stagnant water, the process is sooner finished, but it is more hazardous, and gives a deeper stain to the fibres, than in a stream, which carries off much of the colour. The best place for steeping flax is a pond with springs of water at its bottom; or a tank into which a rivulet of water can be occasionally admitted, while the foul water is let off. For every fresh quantity of flax, the pond should be emptied, and supplied with clear water. Water impregnated with iron, stains flax a permanent colour, and should therefore never be used. After retting, the flax should be taken out without delay, rinsed in clean water, and exposed in an airy situation to dry by the sun.

Rough rippled flax stalks, well seasoned before being retted, and dried afterwards, show a loss of weight, amounting to 20 or 30 per cent., affecting both the boon and the harl. This loss is greater the finer the stems, and the longer the retting. The harl contains, beside the textile filaments, a certain portion of a glutinous cement; but nothing soluble in water. The destruction of the gluten cannot be pushed to the last point by steeping, without doing an essential injury to the filaments.

Dew-retting.--The fetid and noxious exhalations which the water-retting diffuses over an extensive district of country, and the danger of over-retting in that way, especially with stagnant water, are far from recommending that process to general adoption. Dew-retting accomplishes the same purpose, by the agency of the air, dews, and rain, in a much more convenient, though far slower manner. The flax, with this view, should be spread out thin upon meadow or grass lands, but never upon the bare ground, and turned over, from time to time, till the stems, on being rubbed between the fingers, show that the harl and the boon are ready to part. The duration of dew-retting is, of course, very various, from 2 to 6, or 8 weeks, as it depends upon the state of the weather; a moist air being favourable, and dry sunshine the reverse. The loss of weight by dew-retting is somewhat less than by water-retting; and the textile fibres are of a brighter colour, softer and more delicate to the touch.

Mixed retting.--This may be fairly regarded as the preferable plan, the retting being begun in the water, and finished in the air. The flax should be taken out of the steep whenever the acetous fermentation is complete, before the putrid begins, and exposed, for 2 or 3 weeks, on the grass.

II. The breaking is performed by an instrument called a brake. In order to give the wood or boon such a degree of brittleness as to make it part readily from the harl, whereby the execution of this process is rendered easy, the flax should be well dried in the sun, or what is more suitable to the late period of the year, in a stove. Such is often attached to the bakers’ ovens in Germany, and other flax-growing countries. The drying temperature should never exceed 120° F., for a higher heat makes it brittle, easy to tear, and apt to run into tow. Before subjecting the flax to the brake, the stems should be equalized and laid parallel by the hand, and the entangled portions should be straightened with a coarse heckle. The brake has one general construction, and consists of two principal parts, the frame or case, and the sword or beater. In the simplest brakes, the frame e, fig. 412., is a piece of wood cleft lengthwise in the middle, supported by the legs a and c. The sword f, also of hard wood, is formed with an edge beneath, and turns round the centre of motion at q, when seized by the handle h, and moved up and down. As it descends, the sword enters the cleft of the frame, and breaks the flax stalks laid transversely upon it, scattering the boon in fragments.

But those hand brakes are more convenient which are provided with a double cleft, or triple row of oblong teeth; with a double sword. This construction will be understood by inspecting figs. 412, 413, 414. Fig. 412. is the section of that side at which the operative sits; fig. 413. is a section in the line A, B, of fig. 412; and fig. 414., the ground plan. The whole machine is made of hard wood, commonly red beech. Two planks, a and c, form the legs of the implement. a is mortised in a heavy block, to give the brake a solid bearing; two stretchers d, bind a and c, firmly together. The frame e consists of three thin boards, which are placed edgewise, and have their ends secured in a and c. The sword f is a piece of wood, so chamfered from i to k, that it appears forklike, and embraces the middle piece of the frame; its centre of motion is the wooden pin q; in front is the handle h, which the operative seizes with the right hand. Both the lathes of the frame, and those of the sword are sharpened, from l to the front end, as is best shown in fig. 413.; but the edges must not be too sharp, for fear of injuring the flax; and, for the same reason, the sword should not sink too far between the lathes of the frame. Such hand-brakes are laborious in use, and often tear the harl into tow. The operative, usually a female, in working the brake, seizes with her left hand a bundle of flax, lays it transversely across the frame, and strikes it smartly with repeated blows of the sword, pushing forwards continually new portions of the flax into the machine. She begins with the roots, turns next round the tips, then goes on through the length of the stalks. Flax is frequently exposed twice to the brake, with a stove drying between the two applications.

The brake machines afford a far preferable means of cleaning flax than the above hand tools. The essential part of such a machine, consists in several deeply fluted rollers of wood or iron, whose teeth work into each other, and while they stretch out the flaxen stalks betwixt them, they break the wood or boon, without doing that violence to the harl which hand mechanisms are apt to do. The following may be regarded as one of the best constructions hitherto contrived for breaking flax. Fig. 415. is a view of the right side of this machine. Fig. 416., the view from behind, where the broken flax issues from between the rollers. The frame is formed by the two side pillars or walls a, a, which are mortised into the bottom b, b; and are firmly fixed to it by braces. Two transverse rods d, d, secure the base, two others d´ d´´, the sides. In each of these a lateral arm e, is mortised in an oblique direction; a cross bar f, unites both arms. Fig. 417. shows the inside of the left side of the frame, with the subsidiary parts. The three rollers g, i, k, may be made of red beech, with iron gudgeons, and fluted in their length, each of the flutes being 5/12 of an inch broad, and 4/12ths deep. The large roller g, bears upon the right side, a handle h, which on being turned, sets the whole train in motion. The side partitions a, a, are furnished with brasses in whose round holes l, g, fig. 417., the gudgeons g work. For the extremities of the two smaller rollers, there are at a and e, slots in brasses, as may be seen in fig. 415. Within the partition a, there are movable brasses l, for the pivots of i and k, shewn in fig. 417. Each brass slides in a groove, between two ledges. A strong cord made fast at m to the partition a, runs over the brass of i, next over that of k, then descends perpendicularly, and passes over the cross bar n, fig. 415. and 416. This construction being repeated at both ends of the rollers, the rod n, binds both cords. Against the cross bar d´ of the frame, a lever o is sustained, which lies upon the rod n, and carries a weight p. The farther or nearer this weight hangs towards the end of the lever, it stretches the cord more or less, and presses by means of the brasses l, the rollers i, k, towards the main roller g. A table q, serves for spreading out the flax to be broken, and a second one r, for the reception of the stalks at their issuing from between the rollers. Both tables hang by means of iron hooks to rings of the frame s, t, fig. 415. and 417., and are supported by the movable legs u, u, u, fig. 415. and 416. In using the machine the operative lays an evenly spread handful of flax upon the table q, introduces their root ends with his left hand between the rollers g and i, and turns round the handle h, with the right. The stems are first broken betwixt g and i, then between g and k, and come out upon the table r. The handle is moved alternately forwards and backwards, in order that the flax may be rolled alternately in the same directions, and be more perfectly broken. The boon falls down in very small pieces, and the harl remains expanded in parallel bands. This should be drawn over the points of a heckle, then laid for a couple of days in a cellar to absorb some moisture, and afterwards worked once more through the machine, whereby the flax acquires a peculiar softness.

The advantages of this brake machine are chiefly the following:--

It takes up little room, and from its simplicity is easily and cheaply constructed; it requires no more power to work, than the ordinary hand-brake; it tears none of the filaments, and grinds nothing except the boon, in consequence of the flutings of the rollers going much less deep into each other, than the sword of the hand-brake; it prevents all entanglements of the flax, whence in the subsequent heckling the quantity of short fibres or tow is diminished; and it accomplishes the cleaning of even the shortest flax, which cannot be well done by hand machines.

The comminution of the boon of the stems, which is the object of the breaking process, can however be performed by threshing or beating, although in this way the separation of the woody matter from the textile fibres is much less completely effected.

It is the practice in Great Britain, instead of breaking, to employ a water-driven wooden mallet, between which and a smooth stone the flax is laid. In that part of Belgium where the preparation of flax has been studied, the brake is not used, but beating by means of the Bott-hammer, to the great improvement, it is said, of the flax. The Bott-hammer, fig. 418., is a wooden block, having on its under face, channels or flutings, 5 or 6 lines deep, and it is fixed to a long bent helve or handle. In using it, a bundle of the dried flax stalks is spread evenly upon the floor, then powerfully beaten with the hammer, first at the roots, next at the points, and lastly in the middle. When the upper surface has been well beat in this way, it is turned over, that the under surface may get its turn. The flax is then removed, and well shaken to free it from the boon.

By the brake or the hammer the whole wood is never separated from the textile fibres, but a certain quantity of chaffy stuff adheres to them, which is removed by another operation. This consists either in rubbing or shaking. The rubbing is much practised in Westphalia, and the neighbouring districts. In this process, the operative lays the rubbing apron on a piece of dressed leather, one foot square, upon her knee; then seizes a bundle of flax in the middle with her left hand, and scrapes it strongly with the Ribbe-knife held in her right, fig. 419. This tool, which consists of a wooden handle s, and a thin iron blade r, with a blunt and somewhat bent edge, acts admirably in cleaning and also in parting the filaments, without causing needless waste in flax previously well broken.

The winnowing, which has the very same object as the rubbing, is, however, much more generally adopted than the latter. Two distinct pieces of apparatus belong to it, namely, the swing-stock and the swing-knife. The first consists of an upright board with a groove in its side, into which a handful of flax is so placed that it hangs down over half the surface of the board. While the left hand holds the flax fast above, the right carries the swing-knife, a sabre-shaped piece of wood from 1-1/2 to 2 feet long, planed to an edge on the convex side, and provided with a handle. With this knife the flax is struck parallel to the board, with perpendicular blows, so as to scrape off its woody asperities. The breadth of the swing-knife is an important circumstance; when too narrow it easily causes the flax to twist round it, and thereby tears away a portion of the fibres. When 8 or 10 inches broad, it is found to act best. Knives made of iron will not answer, for they injure the filaments.

Figs. 420, 421. show the best construction of the swing-stock. The board a has for its base a heavy block of wood b, upon which two upright pins e e, are fixed. The band f, which is stretched between the pins, serves to guide the swing-knife in its movements, and prevent the operative from wounding his feet. The under edge of the groove c, upon which the flax comes to be laid, is cut obliquely and rounded off (see d in fig. 420.); thus we perceive that the swing-knife can never strike against that edge, so as to injure the flax.

Fig. 422. exhibits the form of a very convenient implement which is employed in Belgium instead of the swing-knife. It is a sort of wooden hatchet, which is not above two lines thick, and at the edge g h is reduced to the thickness of the back of a knife. The fly k gives force to the blow, and preserves the tool in an upright position. The short flat-pressed helve i is glued to that side of the leaf which in working is turned from the swing-stock; and is, moreover, fastened with a wooden pin.

The rubbing and swinging throw off the coarsest sort of tow, by separating and shaking out the shortest fibres and those that happen to get torn. That tow is used for the inferior qualities of sacking, being mixed with many woody fibres.

We may in general estimate that 100 pounds of the stalks of retted flax, taken in the dry state, afford from 45 to 48 pounds of broken flax, of which, in the swinging or scutching, about 24 pounds of flax, with 9 or 10 pounds of scutch tow are obtained. The rest is boon-waste. The breaking of 100 pounds of stalks requires, in the ordinary routine of a double process by hand, about 20 hours; and with the above described machine, from 17 to 18 hours. To scutch 100 pounds of broken flax clean, 130 hours of labour are required by the German swinging method.

Mr. Bundy obtained a patent in 1819, for certain machinery for breaking and preparing flax, which merits description here. Fig. 423. A A A A, is the frame made either of wood or metal, which supports the two conical rollers B and C. These revolve independently of each other in proper brass bearings. A third conical roller D is similarly supported under the top piece E of the machine. All these rollers are frusta of cones, made of cast iron. Whatever form of tooth be adopted, they must be so shaped and disposed with regard to each other as to have considerable play between them, in order to admit the quantity of flax stem which is intended to be broken and prepared. The upper piece E of the machine which carries the upper conical roller D, is fixed or attached to the main frame A A A A by strong hinges or any other moveable joint at G, and rods of iron or other sufficiently strong material; H H is attached at its upper end by a joint to the top piece E, through a hole near I, and is fixed at its lower end by another joint K to the treadle or lever K L, which turns upon the joint or hinges M. A spring or weight (but the former is preferable for many reasons) is applied to the machine in such manner, that its action will always keep the upper piece E, and consequently the upper roller D, in an elevated or raised position above the rollers B and C, when the machine is not in action; and of course the end L of the treadle will also be raised, which admits of the flax to be worked being introduced between the rollers, viz. over the two lower rollers B, C, and under the upper roller D; such a spring may be applied in a variety of ways, as between the top piece E, and the top or platform of the machine at N; or it may be a strong spiral wire spring, having its upper end fastened to the platform while its lower extremity is fixed to the rod H H, round which it coils as shown at O, or it may be placed under the end L of the treadle; but in every case its strength must be no more than will be just sufficient to raise the upper roller D about two inches from the lower rollers, otherwise it will occasion unnecessary fatigue to the person working the machine.

The manner of using it is as follows: the upper and lower rollers being separated as aforesaid, a small handful of dried flax or hemp stems is to be introduced between them, and held extended by the two hands, while the rollers are brought together by the pressure of the foot upon the treadle L. This pressure being continued, the flax or hemp is to be drawn backwards and forwards by the hands between the rollers, in a direction at right angles to their axes, and eventually withdrawn by pulling with one hand only. The foot is now to be removed until the flax or hemp is again replaced, and each end is this way to be drawn several times through the machine, until such ends are respectively finished.

By a succession of these operations, using the pressure of the foot upon L, each time that the flax or hemp is introduced between the rollers, and regulating such pressure according to the progress of the work, the flax or hemp will soon be sufficiently worked, and the fibre brought into a clean and divided state fit for bleaching; or if it be required to spin it in the yellow state, it may be made sufficiently fine by a longer continuation of the same process, particularly if worked between the smaller ends of the rollers.

Indeed, the operation may be commenced and continued for some time, with the larger part of the rollers, and finished with their smaller ends; and, in this point of view, the invention of conical rollers will be found both convenient and useful; for as the flutes, grooves, or teeth, vary in their distance from each other at all points between the large and small ends, so it becomes almost impossible for the workman to draw the flax or hemp through such rollers in the same track; and thus the breaking of the boon must be much more irregular, and the fibre will be much more effectually cleansed than it can be by the flutes, grooves, or teeth of cylinders, or other such contrivances formerly employed; because they would probably fall frequently upon the same points of the fibres. If it is intended that the flax shall be bleached before it is spun, then the second part of Mr. Bundy’s invention may be had recourse to, which consists in moving certain trays or cradles in the water, or other fluid used for bleaching the flax or hemp, in the manner following, viz.: The flax or hemp, after having been broken and worked in the machine, should be divided into small quantities of about one ounce each, and these should be tied loosely in the middle with a string, and in this state laid in the trays or cradles, and then be soaked in cold soft water for a day or two, when each parcel should be worked separately, while wet, through a machine, precisely similar to that already described, except only that the rollers should be cylindrical, and made entirely of wood with metal axles, and the teeth, which will be parallel, should be similar in form to those shown in section at Q, fig. 423*. Such operation will loosen the gluten and colouring matter, for the rinsing and wringing which must follow. The flax must then be again disposed in a flat and smooth manner, in such trays or cradles, and once more set to soak in sufficient soft water to cover it, in which a small quantity of soap, in the proportion of about seven pounds of soap to each hundred weight of flax, has been previously dissolved, and in this state it should remain for two or three days longer, and then be finally worked through the machine, rinsed with clear water, and wrung; which will render it sufficiently white for most purposes.

III. The Heckling.--We have already stated that, by the operation of heckling, a three-fold object is proposed: 1. the parting of the filaments into their finest fibrils; 2. the separation of the short fibres which are unfit for spinning; 3. the equable and parallel arrangements of the long filaments. The instrument of accomplishing these objects is a comb-fashioned tool, called the heckle or hackle; a surface studded more or less thickly with metal points, called heckle teeth; over which the flax is drawn in such a way that the above three required operations may be properly accomplished.

The common construction of the heckle is the following: (see fig. 424.) Fig. 424. is the ground plan, and fig. 425. is the section. Upon an oblong plank a b, two circular or square blocks of wood c and d are fixed, in which the heckle teeth stand upright. To give these a firmer hold they are stuck into holes in a brass or iron plate, with which the upper surface of c and d is covered. Both heckles may be either associated upon one board or separated; and of different finenesses; that is, the teeth of the one may be thinner, and stand closer together; because the complete preparation of the flax requires for its proper treatment, a two-fold heckling; one upon the coarse, and one upon the fine heckle; nay, sometimes 3 or 4 heckles are employed of progressive fineness. The heckle teeth are usually made of iron, occasionally of steel, and from 1 to 2 inches long. Their points must be very sharp and smooth, all at an equal level, and must all graduate very evenly into a cylindrical stem, like that of a sewing needle, without any irregularity. The face of the heckle block must be uniformly beset with teeth, which is done by different arrangements, some persons setting them in a circle, and others in parallel rows; the former being practised in Germany, the latter in England. The coarse heckle is furnished with teeth about one tenth of an inch thick, one and a quarter of an inch long, and tapering from the middle into a very fine point. In the centre of the circular heckle is a tooth planted; the rest are regularly set in 12 similar concentric circles, of which the outermost is 5-3/4 inches in diameter. The fine heckles contain no fewer than 1109 teeth. Instead of making the points of the teeth round, it is better to make them quadrangular, in a rhombus form, in which case the edges serve to separate or dissect the fibres.

The operation of heckling is simple in principle, although it requires much experience to acquire dexterity. The operative seizes a flock of flax by the middle with the right hand, throws it upon the points of the coarse heckle, and draws it towards him, while he holds the left hand upon the other side of the heckle, in order to spread the flax, and to prevent it from sinking too deeply among the teeth. From time to time the short fibres or tow sticking to the teeth are removed. Whenever one half of the length of the strake of flax is heckled, it is turned round to heckle the other half. This process is repeated upon the fine heckle. From 100 pounds of well-cleaned flax, about 45 or 50 pounds of heckled flax may be obtained by the hand labour of 50 hours; the rest being tow, with a small waste in boony particles and dust. The process is continued, till by careful handling little more tow is formed.

Many contrivances have been made to heckle by machinery, but it may be doubted whether any of them as yet make such good work with so little loss as hand labour. In heckling by the hand, the operative feels at once the degree of resistance, and can accommodate the traction to it, or throw the flax more or less deep among the teeth, according to circumstances, and draw it with suitable force and velocity. To aid the heckle in splitting the filaments, three methods have been had recourse to; beating, brushing, and boiling with soap-water, or an alkaline lye.

Beating flax either after it is completely heckled, or between the first and second heckling, is practised in Bohemia and Silesia. Each heckled tress of flax is folded in the middle, twisted once round, its ends being wound about with flaxen threads; and this head, as it is called, is then beat by a wooden mallet upon a block, and repeatedly turned round till it has become hot. It is next loosened out, and rubbed well between the hands. The brushing is no less a very proper operation for parting the flax into fine filaments, softening and strengthening it without risk of tearing the fibres. This process requires in tools, merely a stiff brush made of swines’ bristles, and a smooth board, 3 feet long and one foot broad, in which a wooden pin is made fast. The end of the flax is twisted two or three times round this pin to hold it, and then brushed through its whole length. Well heckled flax suffers no loss in this operation; unheckled, only a little tow; which is of no consequence, as the waste is thereby diminished in the following process. A cylindrical brush turned by machinery might be employed here to advantage.

The boiling of flax with potash lye alone, or with lye and soap, dissolves that portion of the glutinous cement which had resisted the retting, completes the separation of the fibres, and is therefore a good practical means of improving flax. When it is performed upon the heckled fibres, a supplementary brushing is requisite to free it from the dust, soapy particles, &c.

Can flax be prepared without retting?--The waste of time and labour in the steeping of flax; the dyeing of the fibres consequent thereon, which must be undone by bleaching; the danger of injuring the staple by the action of putrescent water; and, lastly, the diminished value of flax which is much water-retted, are all circumstances which have of late years suggested the propriety of superseding that process entirely by mechanical operations. It was long hoped, that by the employment of breaking machines, the flax merely dried could be freed from its woody particles, while the textile filaments might be sufficiently separated by a subsequent heckling. Experience has, however, proved the contrary. The machines, which consisted for the most part of fluted rollers of iron or wood, though expensive, might have been expected to separate the ligneous matter from the fibres; but, in the further working of the flax no advantage was gained over the water-retting process.

1. Unretted flax requires a considerably longer time for breaking than retted, under the employment of the same manipulations.

2. Unretted stalks deliver in the breaking and heckling a somewhat greater product than the same weight of flax which has been retted; but there is no real advantage in this, as the greater weight of the unretted flax consists in the remainder of ligneous or glutinous matter, which being foreign to the real fibre, must be eventually removed. In the bleaching process, the water and the alkaline lyes take away that matter, so that the weight of the bleached fibre is not greater from the unretted than the retted flax.

3. The parting of the fibres in the unretted stalks is imperfectly effected by the heckling, the flax either remains coarser as compared with the retted article, and affords a coarser thread, or if it be made to receive greater attenuation by a long continued heckling, it yields incomparably more torn filaments and tow.

4. The yarn of unretted flax feels harder, less glossy, and rougher; and, on account of these qualities, turns out worse in the weaving than the retted flax. Nor is the yarn of unretted flax, whether unbleached or bleached, in any degree stouter than the yarn of the retted flax.

5. Fabrics of unretted flax require for complete bleaching about a sixth less time and materials than those of the retted. This is the sole advantage, but it is more than counterbalanced by the other drawbacks above specified.

In Mr. Wordsworth’s improved apparatus for heckling flax and hemp, a succession of stricks is subjected to the operation of several series of revolving heckles of different degrees of fineness, for the purpose of gradually separating or combing the long fibres, and dressing them smooth; while at the same time, the tow or entangled refuse portions of the material taken off from the stricks by the heckle points are removed from the heckles by rotatory brushes and rollers covered with wire cards, and discharged into suitable receivers, whence it may be taken to a carding engine, to be worked in the ordinary way.

The accompanying figures represent in plan and section, the heckling machine which is made double, for the purpose of allowing two series of stricks of flax to be acted upon at one time. Fig. 426. is a horizontal view of the machine; fig. 427. is an end view, the whole being represented in working order, and the respective letters of reference pointing out corresponding parts of the machine.

A A are two large barrels or drums, upon the surfaces of which are fixed longitudinally several series of brass ribs a, b, c, d, e, f, g, h, i, holding heckle points. These ribs are placed at small distances apart round the barrels, all the heckle points standing radially from the axes, and the barrels are mounted upon axles supported by pedestals, with plummer blocks bearing on the rails of the end frames. B B, are two horizontal wheels or pulleys turning upon vertical shafts, which pulleys conduct an endless chain C C C C, carrying the holders, whereon the stricks of flax or other material intended to be heckled are suspended.

At one end of the axle of each of the barrels a toothed wheel D D, is made fast, and these are connected by a similar wheel E, and a pinion F, fig. 427., the latter being fixed upon the axle of the driving rigger G.

The power of a steam engine, or any other first mover, being applied by a band and rigger, or otherwise to the axle of G, the pinion F, is driven round, which, being in geering with the toothed wheels E and D D, causes the heckle barrels A A to revolve simultaneously in opposite directions, as shown by the arrows in fig. 427.

The stricks of flax intended to be operated upon are severally confined between pairs of clamps k, fastened together, which clamps, with the stricks, are then suspended in their respective holders H H, attached to the endless chain C: the lower portion of the flax hanging down for the purpose of being acted upon by the rotatory heckles, while the upper portions are turned up in loops and confined by spring levers attached to each carrier.

The respective holders of the clamps consist of a forked frame, with hooks at the lower parts of their arms, which receive the ends of the clamps k, that confine the strick of flax. From the upper part of each forked frame, a perpendicular pin extends, which pins when inserted into the sockets l l l, in front of the chain, form axles for the frames to turn upon at certain periods of the operation.

On the upper end of each pin, a small arm or tappet piece m, fig. 427., is fixed, standing at right angles to the face of the forked frame of the holder H. Those tappets as the endless chain conducts the holders along at certain periods, come in contact with stationary pins or wipers n n, fixed to the guide rails o, on which the chain C slides; and these wipers acting against the tappets as they pass, cause the holders to be turned round at those periods for the purpose of bringing the reverse side of the strick of flax on to the heckle points.

Let it now be supposed, that all the holders connected to the endless chain have been furnished with stricks of flax, or other material to be heckled, and that the barrels A A, are put in motion in the way described, revolving in the direction of the arrows shown in fig. 427. A pinion on the end of the axles of one of the barrels A, will drive a train of toothed geer J K L M and N, on the axle of the latter, of which there is a bevelled pinion taking into a bevelled wheel, turning horizontally at the lower end of the perpendicular shaft of one of the chain pulleys. It will hence be perceived that as the barrels go round, such rotatory motion will be communicated to the pulley B, as will cause it to drive the chain C forward, and by that means conduct the several stricks of flax progressively along the barrel.

When each successive holder, with its strick of flax or other material, is brought to the part z, fig. 426., the fibres come in contact with the rotatory barrel, and first strike upon the series of coarse heckles a a, placed upon an inclined or conical surface of the barrel, by which means the lower ends of the flax in each strick are first acted upon; and as it advances, the upper part, and ultimately the whole length of the long fibres of the suspended strick are gradually brought on to the heckles, which progressive operation prevents the long fibres from being broken, and causes a smaller quantity of tow to be produced than is usually taken off in any of the ordinary modes of heckling.

After the strick of flax or other material has been carried by the travelling chain past the first inclined or conical surface a, of the heckling barrel, it then comes upon the cylindrical part b, of the barrel, which is also furnished with coarse heckles that penetrate and comb down the whole pendant lengths of the fibres. But in order that both sides of the strick of flax may be equally operated upon, the holder is now to be turned round upon its pin or pivot, which movement is effected by one arm of the lever or tappet m, (as the carrying chain moves onward), coming against the stationary pin or wiper n, which changes the position of the holder, as shown at p, in the horizontal view fig. 426.

The under part of the guide rail o, upon which the chain slides, is at this part cut away, for the purpose of allowing the holder to turn round horizontally; and a pin or projection at the under side of the guide rail, as the chain continues moving, acts against the side of the carrier frame, and forces it into a position parallel with the chain. The other side of the strick of flax is by these means brought on to the heckles of the second inclined or conical surface of the barrel at c; and the travelling chain proceeding onward, the fibres of the material are in succession passed over and combed by the heckles of increasing fineness, d, e, and f, on the cylindrical part of the revolving barrel, until the strick having arrived at the second wiper n, the frame or holder is at q, turned round as before, and the reverse side of the strick, or that first operated upon by the heckles a and b, is brought progressively on to the heckles of increasing fineness, g, h, and i; and having passed the last series of rotatory heckles, the holders are in succession to be removed from the machine, the material having been sufficiently dressed.

The clamps of the holders are now opened by the attendant, and the stricks of flax or other material are taken out, and again placed between the clamps in reversed positions, in order that the other ends of the fibres may be operated upon. The clamps, with the stricks, are then suspended again in the holders, the uncombed ends of the fibres hanging down upon the heckle barrel.

In order to avoid interrupting the continual operation of the machine, it is proposed that the strick, on its second introduction, shall be placed in the holders on the opposite side at y, which is one of the reasons for constructing a double machine, and the strick being thence carried along by the travelling endless chain in the way already described, the fibres will be first brought under the operation of the coarse heckles on the inclined or conical surface of the second revolving barrel, and then of the other heckles increasing in fineness on the cylindrical part of the barrel, until having reached the end, as in the former instance, the fibres of the flax may be considered to be sufficiently dressed, and may then be withdrawn.

It may be necessary here to remark, that as different kinds and qualities of material will require different degrees of working by the heckles, this can be effected by varying the comparative speeds of the travelling holders and the heckle barrels. These comparative speeds, it will be perceived, depend upon the diameters of the wheels and pinions by which the pulley B is driven from the rotation of the heckle barrel. These wheels and pinions are therefore intended to be removed and changed for others of different diameters, as circumstances may require. It will be perceived that the faster the stricks travel through the machine compared to the rotatory speed of the heckle barrels, so much the less will the material be acted upon by the rotatory heckles; but as different qualities of material must be differently operated upon, according to circumstances, it is impossible to set out any definite speeds or proportions of speed: that will, however, be readily perceived by competent workmen when working at the machine.

In the process of opening the fibres of the material by the rotatory heckles, a quantity of short or loose fibres, as tow, will be taken off the stricks by the heckle points, and will remain adhering to the barrel between the points of the heckles: in order, therefore, to remove this tow, or other loose entangled materials from the heckles, several series of brushes, or blocks, with bristles, are affixed longitudinally to rotatory barrels Q Q.

These brush barrels are mounted parallel to the heckle barrels upon axles, supported in plummer blocks affixed to brackets extending from the end frames of the machine. Those parts of the brush barrels which are opposite to the cylindrical portions of the heckle barrel are cylindrical, and those parts which are opposite to the bevels are contra-bevelled, or made as frustums of cones reversed, or in an opposite angle, as r, s, so as to run parallel to the inclined surfaces of the heckle barrels a and c.

Upon the periphery of these barrels Q Q, ribs or blocks, with bristles or brushes, are fixed longitudinally, at suitable distances apart, the bristles all standing radially from the axle, and taking into the points of the heckles.

Rotatory motions are given to the brush barrels Q Q, by bands passing from the riggers at G, over pulleys R R, fixed at the end of each of the axles of the brush barrels. Hence, it will be perceived, that the barrels Q Q will revolve in opposite directions to the heckle barrels, and with sufficient speed to enable the brushes to pass through between the points of the heckles, and in so doing, to remove the tow or other loose matter therefrom.

The tow or other loose fibrous material collected upon the brushes is transferred thence on to wire cards placed round the periphery of the barrels S S, which barrels are mounted upon axles parallel to the brush rollers, and turn in plummer blocks upon brackets, extending from the end frames of the machine.

These barrels are cylindrical, and covered with sheets of wire cards at those parts which are opposite to the cylindrical portions of the brush barrels, but those portions of the barrel S, which are opposite to the bevelled points r and s, of the brush barrels, are bevelled or made conical at t u, to fit or correspond with the inclined surfaces r and s; these are covered with sheets of wire card also.

Rotatory motions are communicated to the card barrels S S, by bands from the pulley T, fixed on to the side of the toothed wheel M, (see fig. 427.) which band drives similar pulleys V V, mounted upon studs fixed in the end frame. Upon the side of each of these pulleys V V, a pinion t is fixed, which pinion takes into the teeth of the wheel W, on the end of the axle of each of the card barrels S S; by which means such slow motions are given to the barrels S, as will allow the brushes of the barrels Q to comb off, and deposit the tow or other fibrous material upon the wire cards as they revolve, and from whence it is to be removed by a doffing comb, and let fall into any convenient receptacle below, in the same way as in ordinary carding engines.

The doffing combs, X X X, are formed to the shape of the card barrels, and are attached to straight bars extending along the machine on both sides, which are supported at their extremities by levers Y Y, vibrating upon fulcrum pivots at w w. To these levers perpendicular rods Z Z are connected by joints, and the lower end of each of these rods is attached to an eccentric disk, roller or crank x x, on the axle of the brush barrel; whence it will be perceived that by the rotation of the eccentrics x, the levers Y will be made to vibrate and strike off, or doff the tow or other material from the card barrels, in a similar manner to the operations of the doffing comb of an ordinary carding engine.

Mr. Evans’ patent improvements in machinery for preparing and dressing flax and hemp apply, first, to the operation of scutching, swingling, or beating away the boom or woody particles of the rind which covers the flax, or hemp, in its rough state; and, secondly, to the subsequent operation of heckling, combing, or opening of the fibres of the material preparatory to spinning it into yarns.

Fig. 428. represents the scutching or swingling machine, in different positions. Fig. 428. is an end view of the machine in operation; fig. 429. is a front view of the same. The essential parts of the machine, and those in which the invention especially consists, are two pairs of revolving beaters or scutchers, each formed by long ribs or blades mounted upon arms. The blades of the beaters a a, may be made of ribs of hard wood, or other suitable material, broad but thin, and slightly rounded on their edges, to prevent their cutting the fibres of the flax or hemp when they strike it. The two blades are placed parallel to each other, and mounted upon a hexagonal frame, the arms b b inclining or forming obtuse angles with the blades, and from the middle of the arms short axles c c, extend, upon which the beaters revolve.

The axles of both pairs of beaters are mounted in plummer boxes, bearing upon horizontal rails at the ends of the machine, as shown in fig. 428., and are at such distance apart as will allow of the arms and the beaters of each pair passing alternately within those of the other pair as they revolve in opposite directions, which they are enabled to do without coming in contact, in consequence of the inclination of the arms.

On the axle at one end of each pair of beaters a toothed wheel d, is affixed, and these wheels being of similar diameters, and taking into each other, cause the beaters to revolve with similar speed in opposite directions, rotatory motion being given to them by a band and rigger fixed upon one of the axles; and in order that the beaters in revolving may not come in contact as they pass, the positions of the two pairs are so arranged that the blades of one shall be in a perpendicular situation, while those of the other are horizontal.

The rind of the flax or hemp having been previously broken by any of the ordinary modes of performing that operation, small bunches or stricks of the material are spread out, and their ends confined between the jaws of clamps or holders.

These clamps or holders differ considerably from the clamps which are commonly used. I shall therefore particularly describe their construction, before showing them in operation. Fig. 430. and 431. are views of the clamp in two different positions; a and b are two boards united together by a hinge c, at top, which of course allows them to shut and open. The lower parts, forming the jaws of the clamps, are made with teeth or indentations, between which parts the ends of the flax or hemp are securely held when the clamps are brought together; d d, are two pieces projecting from the board b, at the end of each of which is an eye shown by dots, and at the back of the board a, (see fig. 430.,) there is a double armed lever e, turning upon a fixed pin f, which lever carries two circular wedges g g. These wedges pass into the eyes of the pieces d d, when the clamps are closed, and hold them fast. There is a segment ratchet h, at the upper part of the board a, which turns upon a stud i, and is pressed downward by a spring k. This ratchet receives the end of the lever e, and consequently keeps the circular wedges firm in the eyes, which hold the clamps securely together, and prevents their opening by the shaking of the machine.

When it is required to open the clamps, the ratchet h must be raised, and the lever e pushed aside by its handle l, which draws the circular wedges f from the eyes of the pieces d d, and the boards of the clamps immediately separate. For the convenience of suspending the holders in the machines, a piece of sheet iron m, is bent at right angles, and fastened to the back of the board b, as seen in fig. 431., forming a groove by means of which the holders are enabled to slide into the machine and hang there.

These clamps or holders are, when charged with the material, placed in the scutching machine, as shown at e e e in figs. 428. and 429., bearing upon the edge-rail or bar f. The beaters are now made to revolve in the manner already described, by which the edges of the blades will strike against the pendent stricks of flax or hemp alternately on each side, and beat off, scutch or swingle the boom from the material, and render it fit for the operation of heckling which is to follow.

The whole machine is encased with boards, to prevent the inconvenience arising from dust, and an apparatus might be adapted with a blower to conduct away the dust created by the machine, and to discharge it out of the building.

In introducing these stricks of flax or hemp into the machine, the holder is placed upon the projecting end of the bar or edge-rail f, and is thence slidden into the machine; and after the material has been sufficiently scutched or swingled, the holders with the stricks are removed through the top of the machine, and others successively introduced at the end, and pushed along the rail.

If, however, it should be thought desirable, the stricks may be progressively carried through the scutching machine, and delivered into a similar edge-rail in the heckling machine, there to be operated upon in the way about to be described, by which means the whole process of scutching and heckling may go on without interruption.

Fig. 432. represents the heckling or combing machine by which the fibres of the material are to be opened, and the tow removed. It is a transverse section, taken nearly through the middle, in a vertical direction. Perpendicular standards form the ends of the machine, which are connected together by longitudinal rods or bars secured by nuts. The heckle points intended to act upon the flax are mounted in the frames a, b, c, and d, and the stricks of flax held in the clamps e, e, e, as described, are suspended from the bar or edge-rail extending through the machine.

In order to render the principles of this machine and its mode of working evident, it may be desirable to show in an abstract form the manner in which the heckles are brought into operation upon the flax, and for this purpose two diagrams are delineated in figs. 433, 434.

Suppose two sets of combs or heckle points be mounted upon frames a and b, as in these figures, each frame being moveable by means of cranks c, c, and d, d, connected in such manner that they both turn with the same speed in opposite directions, it is evident that every part of the frames and combs will move in circles corresponding to those described by the cranks; the points of the combs travelling in the directions of the arrows, and in circles represented by dots.

During this movement, whilst performing the first descending quarter of the circle, the cranks bring the frames together as in fig. 433. They begin after this to separate in describing the second descending quarter, and come to the position fig. 434., when, continuing to revolve, they move further from each other in describing the first ascending quarter of the circle, and arrive at the position where the distance is the greatest; lastly, they describe the second ascending quarter returning to the third position. If, therefore, a strick of flax be suspended between the two sets of combs as in fig. 433., and the rotatory motion be continued for a sufficient length of time, the flax will be combed in the whole length which is submitted to the actions of the combs, although the points severally have only operated in very small space.

Such a system of combs or heckles would make a very good and simple heckling engine, if it were not for the inconvenience experienced by the points dragging some of the fibres with them when withdrawing from the flax, which would produce a great waste of material; and to obviate this it would be necessary to introduce some contrivance for clearing the points, which must be attended with considerable complication. The plan, however, of the present improved engine, affords the means of producing the same effect by more simple and efficient means.

There are two series of combs, see fig. 435., attached to two movable frames represented at a and b. Each frame is formed by vertical bars a b, with lateral branches or arms, which carry the heckle points. The branches or arms are parallel, and at equal distances apart, but fixed in such positions in each frame that they may occupy the intervening space when the frames are brought together as fig. 436. The frames are put in motion by means of revolving cranks to which they are attached, as shown in fig. 436., and when the cranks turn upon their axes, the branches of one frame pass between those of the other without touching. This forms what may be called a set of combs; but one of the improved machines contains two such sets, the points of the combs of one set being opposed to the points of the combs in the other set.

The way in which the series of combs that compose one set act upon the flax, is shown in the side view, fig. 435. When the cranks are nearly vertical, the points of both frames are away from the flax, but as the cranks move round in the direction of the arrows, the frames come into another position, and it is then that the points or heckles of one of the frames a, begin to penetrate the flax, and descending they comb or divide its fibres. The rotation of the cranks continuing, the two frames a and b come into the position shown at fig. 435., the points of the frame a, withdrawing from the flax, and those of the frame b, approaching and pushing the fibres off from the former, which are now combed by the descending stroke of the points.

It will hence be perceived that as the combs of the frame a and b, respectively advance, they will push forward the whole of the strick of flax, and render it impossible for the fibres to be raised and entangled, as each frame in advancing clears the fibres from the points which preceded it.

A single set, however, of such combs or heckles acting only on one side of the flax, would but imperfectly perform the operation of opening its fibres; it is therefore necessary, in order to accomplish the desired object in the most effectual way, that two such sets of combs or heckles should be brought to act on opposite sides of the strick of flax, which may be done in the manner shown in the figures. The cranks of the two opposite sets of comb-frames or heckles a, b, and c, d, are connected by a pair of toothed wheels e, f, as fig. 437., or by four toothed wheels, by which the heckles are actuated at once, the two sets moving in opposite directions, but with similar speeds, and the combing or heckling of the material will go on in the way shown in the figure last indicated.

Thus far I have considered only two frames of combs or heckles constituting a set, as acting upon each side of the strick of flax; but in order to perform a greater quantity of work, several sets may be mounted in one machine, working alongside of each other, extending over the breadth of the machine. The combs may then be supported upon three frames, of which the middle one may have branches or arms extending upon both sides, and the other two frames branches extending inwards only. To drive the frames so arranged they must be connected to treble cranks.

Such is the principle of the improved machine for combing or heckling, exhibited in the several figures of which I now proceed to describe the particular construction. The machine or engine, fig. 432., has four sets of combs, acting both at the back and front of the flax; a b are the front set of combs, and c d, the back set of combs; e e e, are the clamps holding the stricks of flax previously scutched, which clamps hang upon the edge-rail. The comb frames are attached at top and bottom to the cranks g g, which are all connected by toothed geer, and driven by a band and rigger.

The combs or heckles being put in motion in the way described, act upon the suspended stricks of flax, and upon their fibres, as explained; which stricks are progressively conducted through the machine by their clamps sliding upon the edge-rail through the agency of the endless chain, to which the clamps are severally attached, by a hook falling into one of the links. The chain is driven by a spur wheel upon the axle of a bevel wheel, which receives a slow rotatory motion through a bevel pinion on the axis of a similar wheel, actuated by another pinion on the end of the upper crank axle. By these means, clamps, with the stricks of flax placed on the edge-rail, are slowly carried through the machine, when the flax will be gradually acted upon first by heckle points of a coarse kind, set wide apart, and ultimately by finer points set near together; after which, the clamp with the strick of flax is discharged from the machine, at the reverse end of the edge-rail. But should the workman neglect to remove the holder or clamp, when it arrives at the end of the rail, the machine would be stopped by means of a jointed lever, having a fork at its end, which pushes the band from the fast rigger on to the loose one, and throws off the driving power.

As the combs or heckles, in acting upon the flax to divide its fibres, tear parts of the fibres, and reduce them into tow, the downward motion of the heckles brings the tow with them out of the flax, which is deposited between two fluted rollers p p, fig. 432., and is by them conducted down to the large drum q, where it becomes lapped in two endless sheets round the periphery of the drum; the one of coarse tow, the other of fine, the adhesion being assisted by a pressing roller r; and when a quantity of the tow has been thus accumulated round the periphery of the drum, it may be removed thence by cutting it off in sheets. The fluted rollers, and also the large drum, are driven by geer bands.

After the strick of flax has been thus carried through the scutching machine or the heckling machine, the jaws of the clamps are to be opened, the ends of the flax reversed, and the strick again confined in the clamps, so that the other end of the strick may be operated upon in a similar way. In order to prevent any part of the flax from attaching itself to the branches of the movable frames, each frame is furnished with a shield or guard of polished iron or brass plate, which covers a part of the combs and the heads of the screws by which they are fixed to the branches. When the plate metal is bent into the form of a shield, it is slipped on to the branches of the heckle frames, and is sufficiently elastic to hold fast.

But it is to be observed, that the edges of the shields are to vary in the extent of their projection according to the situation in which they are to be placed; those which are to shield the upper branches of heckles are to project but little, so as to leave the points uncovered and free to enter the strick of flax; but the shields of the lower heckles are to project considerably over the points, to prevent them from penetrating too far into the fibres, which is so contrived for the purpose of facilitating the falling of the tow, which would otherwise be with difficulty removed from the lower combs, were it thrust upon the whole length of the points.

It being advantageous that each strick of flax should be combed near the lower extremities before the middle is acted upon, it is necessary, in order to obtain this effect, to remove some of the points of the combs in the upper branches. By these means, the operation of the heckles upon the flax begins and proceeds gradually, and ceases at the opposite extremity of the machine in the same gradual way, which is very advantageous in clearing completely the flax from the tow.

IV. Flax spinning.--If we compare flax with other spinning materials, such as wool and cotton, we shall find it to possess several characteristic properties. While cotton and wool are presented by nature in the form of insulated fibres, the former requiring merely to be separated from its seeds, and the latter to be purified from dirt and grease before being delivered to the spinner, flax must have its filaments separated from each other by tedious and painful treatment. In reference to the spinning and the subsequent operations, the following properties of flax are influential and important:--

1. The considerable length of the fibres, which renders it difficult, on the one hand, to form a fine, level, regular thread, on the other, gives the yarn a considerably greater tenacity, so that it cannot be broken by pulling out the threads from each other, but by tearing them across.

2. The smooth and slim structure of the filaments, which gives to linen its peculiar polished aspect, and feel so different from cotton, and especially from woollen stuffs, unless when disguised by dressing. The fibres of flax have no mutual entanglement, whereby one can draw out another as with wool, and they must therefore be made adhesive by moisture. This wetting of the fibres renders them more pliant and easier to twist together.

3. The small degree of elasticity, by which the simple fibres can be stretched only one twenty-fifth of their natural length before they break, while sheep’s wool will stretch from one-fourth to one half before it gives way.

Good flax should have a bright silver gray or yellowish colour (inclining neither to green nor black); it should be long, fine, soft, and glistening, somewhat like silk, and contain no broad tape-like portions, from undissevered filaments. Tow differs from flax in having shorter fibres, of very unequal length, and more or less entangled. Hemp agrees in its properties essentially with flax, and must be similarly treated in the spinning processes.

The manufacture of linen and hemp yarn, and the tow of either, may be effected by different processes; by the distaff, the hand-wheel, and spinning machinery. It will be unnecessary to occupy the pages of this volume with a description of the first two well known domestic employments. I shall therefore proceed directly to describe the last method, or

Spinning of Flax by Machinery.--This branch of manufacture has been much more recently brought to a practical state than the spinning of cotton and wool by machines, of which the cause must be sought for in the nature of flax as above described. The first attempts at the machine spinning of flax, went upon the principle of cutting the filaments into short fragments before beginning the operation. But in this way the most valuable property of linen yarn, its cohesive force, was greatly impaired; or these attempts were restricted to the spinning of tow, which on account of its short and somewhat tortuous fibres, could be treated like cotton, especially after it had been further torn by the carding engine. The first tolerably good results with machinery seem to have been obtained by the brothers Girard at Paris, about the year 1810. But the French have never carried the apparatus to any great practical perfection. The towns of Leeds in Yorkshire, of Dundee in Scotland, and Belfast in Ireland, have the merit of bringing the spinning of flax by machines into a state of perfection little short of that for which the cotton trade has been so long celebrated.

For machine spinning, the flax is sometimes heckled by hand, and sometimes by machinery. The series of operations is the following:--

1. The heckling.

2. The conversion of the flax into a band of parallel rectilinear filaments, which forms the foundation of the future yarn.

3. The formation of a sliver from the riband, by drawing it out into a narrower range of filaments.

4. The coarse spinning, by twisting the sliver into a coarse and loose thread.

5. The fine spinning, by the simultaneous extension and twisting of that coarse thread.

The spinning of tow requires a different treatment: we shall first treat of the heckling of flax by machines; and secondly, of the mechanical spinning of flax. The mechanical carding and spinning of tow are very similar to those of cotton; which see. Though machine heckling be far from perfect, yet the tow it throws off can be spun into very good yarn by machines, while it would afford very indifferent yarn to the hand spinner.

All heckle machines have this common property, that the flax is not drawn through them, as in working by hand, but on the contrary, the system of heckles is moved through the flax properly suspended or laid. Differences exist in the shape, arrangement, and movements of the heckles, as also in regard to the means by which the adhering tow is removed from them. The simplest and most common construction is to place the heckles upon the surface of a horizontal cylinder, while the flax is held either by mechanical means or by the hand during its exposure to the heckle points. Many machines have been made upon this principle. It is proper in this case to set the heckle teeth obliquely in the direction in which the cylinder turns, whereby they penetrate the fibres in a more parallel line, effect their separation more easily, and cause less waste in torn filaments. To conduct the flax upon the cylinders, two horizontal fluted rollers of iron are employed, which can be so modified in a moment by a lever as to present the flax more or less to the heckling mechanism. The operator seizes a tress lock of flax with her hand and introduces it between the fluted rollers, so that the tips on which the operation must begin, reach the heckles first, and by degrees the advancing flax gets heckled through two-thirds or three-fourths of its length, after which the tress or strick is turned, and its other end is subjected to the same process. By its somewhat rapid revolution the heckle cylinder creates a current of air which not only carries away the boomy particles, but also spreads out the flax like a sheaf of corn upon the spikes, effecting the same object as is done by the dexterous swing of the hand. The tow collects betwixt the teeth of the heckle, and may, when its quantity has become considerable, be removed in the form of a flock of parallel layers.

The essential parts of such a construction will be understood from fig. 438., though the fluted rollers are absent. The flax a, b, is held by the hand, or in a kind of clamp. The cylinder is partly covered with a curvilinear plate of iron c, d, which serves to sustain the flax, and to guide it in circular tresses round the periphery of the heckle. At the beginning it is placed near b, when the tips of the flax are only presented to the heckles; during the working the shield is continually drawn back in the direction from d to c, and thus lets the operation be performed upon the remaining part of the flax.

First operation; the conversion of flax into ribands or slivers.--This is effected by subjecting the flax to a series of advancing gills or heckle-teeth, and at the same time drawing out its fibres by means of rollers. Figs. 439, 440, 441, show the outline of the construction of a machine for this purpose. Here two rows of heckles are placed alongside of each other, though only one of them be shown in the ground plan, fig. 440., in order to allow the parts beneath the other to be seen. The flax is placed in the sheet iron channels a a, by laying down one handful after another, so that the points of the second strick reach to only the middle of the first, and thus preserve a uniformity of thickness in the feeding. This process is necessary, since, as every one knows, the heckled stricks are always thick in the middle, and thin at the ends. The flax being introduced between the rollers b and c, is drawn out by their agency, and at the same time subdivided by the heckles d, between whose teeth the pins of the roller e press it down. At the rollers _f_³ it is loosened from the heckles by the transverse bars which rise from the springs g, after which it is seized by the rollers h i, and drawn again. A little beyond these rollers, it runs through a funnel l, in order to gather the fibres together; in front of these rollers the slivers from both rows of heckles are united, and proceed in one riband through that polished brass funnel; the rollers m n extend this riband, pressing it gently together, and then let it fall into a tin can. The union of the two slivers contributes to the uniformity, since the irregular thicknesses are thereby compensated. The diameter of the roller c, is equal to that of each of the cylinders f, _f_¹, _f_², _f_³; and the whole five move with equal velocity. The same correspondence exists between the rollers n and i. Thus the sliver of flax is not stretched either by its passage from e, upon the heckles, nor between i and n, but solely in passing from the heckles to the rollers i h. The heckle teeth of this machine do not stand perpendicularly, but are bent somewhat backwards; so as to retain the flax more firmly. The revolving cylindrical brush o, is placed over and a little in front of the pressing roller h, in order to take off all the filaments of flax adhering to their circumference, and to toss them onwards where they may again unite with the slivers. For the sake of perspicuity, the rollers h, and those brushes are left out in fig. 440., but the latter are particularly shown in fig. 442., while a portion of their axis q, is however shown in fig. 440. The pressure of the cylinder h, upon the cylinder i, is produced by the weight r, fig. 439., which hangs upon the lever s; the lever pulls down at t, a vertical rod, whose upper hook-shaped end embraces the axis of h in the middle of its length.

Second principal operation; the formation of rovings.--Mr. Wordsworth’s improvements in machinery for preparing, drawing, and roving flax, hemp, wool, and other fibrous substances, consists in a novel contrivance or mechanism to be adapted to the machine commonly called the gill, employed for preparing, drawing, and roving flax and hemp, and for combing and spinning long wool; which improvements allow the points of the travelling heckles to continue longer in operation than in the ordinary construction of gill, and cause the heckle points to be withdrawn from the fibres at the end of the stroke without the possibility of their drawing the fibres down with them.

The manner of effecting this object will be seen by reference to the several figures which exhibit a gill on this improved plan in different views. Fig. 443. is a plan or horizontal view, exhibiting the upper surface of the machine; and fig. 444. is a longitudinal section taken through the middle of the machine: fig. 445. is a representation of the front of the machine, but in which several parts have been removed to show the action of the heckles more perfectly.

The several heckles a a a are formed by a series of needles or heckle points set into a metal bar, as represented on an enlarged scale in figs. 446. and 447. These bars are each of them suspended in a frame or carriage b b b (shown in two views at figs. 448. and 449.), by means of double jointed levers c c, seen in two positions, at figs. 450. and 451.; the heckle bar, its levers and carriage or frame, being shown put together in figs. 452. and 453.

When the heckles are in operation, the points are raised, as in fig. 452.; but when they are withdrawn from the fibres, then the points are sunk down into the carrying frames, as fig. 453.

These two positions of the heckles are produced by the knobs or parts d, that project from the jointed levers c, acting against the edges of guide bars, which will be explained in describing the operations of the machine.

The several heckles are adapted and made to work in the machine by attaching the ends of the respective frames or carriages b, to travelling endless chains e e, seen in figs. 443., 444., and 445. These endless chains pass over fluted guide rollers f f, seen best in figs. 444. and 445., and over horizontal bars g g, seen best in figs. 443. and 444. The chains with the heckles are driven through the machine by rotatory spur wheels h h; see figs. 443. and 444., the teeth of which take into the spaces between the cylindrical parts of the several heckle carriages b b, and consequently drive the heckles forward; and these spur wheels are actuated by a train of toothed geer from the first driving shaft i, which gives motion to all the operative parts of the machine.

If flax, hemp, long wool, or other fibrous material, be passed into the machine at the back part by a feeding cloth or creeper through a guide k, best seen in figs. 443. and 444., and be conducted under and over the feeding rollers l, m, and n, and over the heckles a a a to the drawing rollers o and p, and thence to the flyer and bobbin, or to a receiving can, the fibres will be opened in their progress, and combed by the points of the heckles entering into and separating the fibres, the material being drawn by a different speed to that with which the heckles travel.

This operation of preparing, drawing, and roving flax and hemp, and the general construction of a machine of this kind being well understood, it is not necessary to explain its details, excepting as respects those parts which constitute the present improvements.

It will be perceived, by reference to figs. 443. and 444., that the knobs d, which project from the jointed levers c, as they travel along the machine, bear against the outer edges of the two fixed guide bars q q that extend along the top of the machine above the heckles, which keep the heckle points raised, as in fig. 451. This will also be very evidently seen in the front view of the machine, fig. 445., where the upper heckle bar a is raised in its carriage b, by the knobs d d bearing against the outer edges of these guide bars q q. But when the endless chains e e, which support and conduct the frames or carriages of the heckles, have advanced the heckle points to within a very little distance of the drawing rollers (see fig. 444.) then the knob d of the jointed levers at each end of the heckle bar passes the ends of the guide bars q q, and they immediately come in contact with two inclined planes r r, seen in figs. 443. and 444., which instantly depress the levers c, and consequently cause the heckle bar a, with its points to descend in the frame or carriage b, withdrawing the points from the fibres of the material almost in a perpendicular direction.

The heckles that have become thus depressed pass with their carriages by the traversing of the endless chains along the under part of the machine, and when they arrive at the back, and begin to rise, the guide bars q q, being at their commencement slightly bent, conduct the knobs b of the levers c until they are forced back into the positions first described, whereby the heckle points are raised, as they come to the upper part of the machine, into effective operation. The fibres of material operated upon, after passing through the drawing process between the rollers, may be roved, twisted, or spun, by the employment of a bobbin and flyer, as shown in fig. 444., or may be delivered into a can, to be roved, twisted, or spun, by other machinery, by substituting a pair of conducting rollers instead of the bobbin and flyer, which shall conduct the sliver of material into a tin can below.

The descent of the heckles a, into their frames b, by the falling of the levers c, c, precludes the possibility of the fibres of the material operated upon being carried down under the machine by the points, as frequently happens in gill machines of the ordinary construction; and this mode of mounting the heckles and traversing them with the assistance of the guide bars q, q, and inclined planes r, r, allows the heckle points to be brought much nearer to the drawing rollers o, p, by means of the metal bars in which the heckle points or needles are set, falling below the centre of the endless chain e, e, as shown in figs. 443. and 444., and thereby affords the means of preparing, drawing, and roving various qualities of flax, hemp, wool and other fibrous materials, particularly such as have a much shorter staple than any fibrous materials hitherto operated upon in gill machinery.

Another most ingenious and effective improvement made of late years in the flax spinning machinery, is that patented by Messrs. Westley and Lawson, in August 1833, and since then introduced into practice with great advantage. It applies to the gill or mechanism employed for opening, straightening, and separating the fibres of flax, hemp, and long wool in the operation of slivering. The peculiar feature here is a method of driving the heckle bars through the gill machine by means of perpetual screws or worm shafts, instead of by chains and spur wheels, as in the former constructions.

The heckle bars which lie across the machine, are, by the present patentees, supported at their ends by fixed horizontal guide rails, on which they slide, while the extremities of the heckle bars are inserted in the helical grooves of the worm shafts, which are placed in horizontal positions at the sides of the machine; and hence the rotatory motions given to these screw shafts, cause the heckle bars to be driven along the guide rails with an uniform simultaneous movement.

The heckle bars having performed their usual office, that is, having combed and separated the fibres of the material as they move onward, are at the front part of the machine depressed and put out of operation by means of rotatory cams; and by the assistance of guide levers, each heckle bar, when it arrives at the end of the upper horizontal guide rail, is conducted down to the lower horizontal guide rails, where the extremities of the comb-bars falling into the helical grooves of a lower pair of worm shafts, revolving in an opposite direction to the former, thereby give the heckle bars a retrograde movement. When they arrive at the back end of their horizontal guide rails, they are, by similar rotatory cams, raised again to the upper horizontal guide rails, which coming into geer with the upper worm shafts, are moved onwards as at first.

By this means a succession of heckles is continually advancing upon the upper guide rails, having their points in constant operation between the fibres of the textile materials, while their vertical position is secured during their whole course.

Fig. 454. is a horizontal representation of a gill machine, shewing the present improvements; but some of the upper portions of the machine are removed, to let the working parts be seen more clearly. Fig. 455. is a side view of the gill; and fig. 456. a vertical section taken longitudinally. The driving rigger or pulley a, is fixed upon the front roller b, commonly called the drawing roller, because when pressed upon by the upper wooden roller c, it draws out the fibres between them. The rollers d, e, f, are the ordinary back or holding rollers, for retaining the fibres, while they suffer powerful traction by the rollers b, c, over the needles or points of the heckle bars. The upper guide rail above mentioned, upon which the heckle bars slide, is shown at g, in fig. 456., and the lower guide rail at h; the series of heckle bars with their needles are represented at i, i, i, i, i, i; the upper worm shafts k, k, are mounted in brackets made fast to the sides of the frame; a similar pair of worm shafts l, being mounted in like manner below. These worm shafts k and l, on each side are connected together by toothed wheels m, and upon the axles of the lower worm shafts, bevelled pinions n are fixed, which take into corresponding bevel pinions on the transverse shaft or axle o. This shaft o, being connected by a train of toothed wheel work with the axle of the drawing roller b, as shown in figs. 454. and 455., the rotation of the roller b, causes the shaft o to turn also, and the bevel geer n and o, produce the rotatory motion of the worm shafts k and l, which turn in contrary directions.

It will be seen, from fig. 454., that the ends of the heckle bars i, have nibs or projections which fall into the grooves of the screw or worm shaft, and that being supported below, upon their guide rails, as the worm-shafts k k revolve, the upper range of heckle bars will be progressively advanced towards the front part of the machine. By referring to fig. 456. it will be perceived, that as each heckle bar arrives at the front end of the guide rail g, a finger p, called a tappet or cam, on the shaft k, strikes it down to the lower guide rails h; and, in order that its descent may be truly vertical, weighted levers q q, in front, are made to press against the face of the heckle bar as it descends. This bar having now arrived at the lower guide rails h, lets fall its nibs into the grooves of the lower worm shafts l, by whose rotation the heckle bar is made to retrograde, or return towards the back of the machine. When the heckle bar has reached the hinder end of the guide rail h, a finger or tappet, r, on the lower worm shaft, comes under it and raises the heckle bar, guided by the back-weighted levers s, as shown in fig. 456., till it is elevated to the level of the upper guide rail g; when the threads of the upper worm-shafts take hold of its nibs as before, and conduct it forward upon the guide rail in the way already described. Thus the continued rotation of the worm shafts k k, and l l, causes the whole series of heckle bars to travel along the guide rails, and the tappets p and r, by alternately depressing and raising them at the ends of the said rails, cause them to move in a regular circuit, yet so as to preserve their verticality.

The claim made under this patent is, for every mode in which screw or worm shafts may be adapted to conduct the bars carrying the needles or heckle-teeth through a machine for preparing, drawing, or roving textile fibres.

In December 1835, Messrs. Hope and Dewhurst obtained a patent for improvements in the manufacture of flax, which deserve notice. These are of both a chemical and mechanical nature. The first consists in steeping the flax in dilute sulphuric acid, of a certain strength, and for a certain time, proportioned to the quality of the fibres, the coarser requiring the stronger application. By this means the gummy matter and the outer shell will be loosened and easily detached. It is then to be passed between squeezing rollers, afterwards well washed, boiled in a solution of soap and water for a few hours, and finally passed again through the rollers. These processes may be repeated till the flax acquires the desired glossiness and separation of fibres. It is next to be beaten, and passed once or twice over an ordinary heckle or stiff brush.

The second part, or the mechanical, is represented by the figures 457., 458., 459., 460., and 461. Fig. 457. is a sectional elevation in part of the construction of the spindle, bobbin and flyer proposed for spinning all kinds of flax or hemp. Fig. 458. answers for spinning coarser yarns; fig. 459. shows how yarns are to be spun for weft, and wound upon what is called a “pin cop bobbin.”

a a a is the stationary or fixed spindle of the ordinary throstle frame, which is surrounded by the tube b b, and connected to the wharve or pulley c, by which the flyer d is driven. The flyer is furnished with guides or conductors e e, which lead the yarn immediately to the bobbin; this flyer is also provided with a small central shaft which supports it, and runs in the small cup or recess at the top of the stationary spindle a, and is fixed with the flyer to the tube b b, which is altogether carried round or driven by the wharve c.

It will be seen by fig. 460., that the wharve c, and tube b, are connected at bottom by a half-lap coupling joint or clutch; this is for the purpose of allowing the tube b to be slidden up the spindle, and more readily removing the bobbin when it is full of yarn, without stopping the frame, or removing the band from the wharve c, the tube of which runs in the step or cup h, fixed upon the bolster rail near the bottom of the throstle frame. The traversing of the bobbin or the copping motion is effected exactly in the same manner as in ordinary throstles, that is, by the lifting and lowering of the copping rail i, which in this instance supports the bobbin. In fig. 458. the flyer is constructed of twice the length of the bobbin, to allow this to rise and fall freely within it, and is connected at top by a slight cross piece, for the purpose of preventing the arms of the flyer from expanding by the centrifugal force, when turning with great velocity. The flyer for spinning coarse numbers requires to have an inner tube k, to support the spindle. The bobbins are supported upon a washer l, l. The spindle is allowed to revolve in a slight degree by the friction of the drag-weight m, m. This weight has a hole formed in it with a flat side, as shown in fig. 461.

Flax has been for a long period spun wet in the mills; a method no doubt copied from the practice of housewives moistening their yarn with their saliva at the domestic wheel. Within a few years the important improvement has been introduced, of substituting hot for cold water, in the troughs through which the fibres in the act of spinning pass. By this means a much finer, smoother, and more uniform thread can be spun than in the old way. The flax formerly spun to twelve pounds a bundle, is, with hot water, spun to six. The inconvenience of the spray thrown from the yarn on the flyers remains; aggravated by increased heat and dampness of the room, where this hot process goes on. Being a new expedient, it receives daily changes and ameliorations. When first employed, the troughs of hot water were quite open; they are now usually covered in, so as almost entirely to obviate the objections to which they were previously liable. With the covers has been also introduced a new method of piecening or joining on any end, which may have been run down, namely, by splicing it to the adjoining roving, whereby it is carried through the water without imposing a necessity on the spinner to put her hand into the water at all. In some places she uses a wire, for the purpose of drawing through the end of the roving to mend a broken yarn.

This may be considered the inherent evil of flax-spinning,--the spray thrown off by the wet yarn, as it whirls about with the flyer of the spindles. A working dress, indeed, is generally worn by the spinners; but, unless it be made of stuff impermeable to water, like Macintosh’s cloth, it will soon become uncomfortable, and cause injury to health by keeping the body continually in a hot bath. In some mills, water-proof cloth and leather aprons have actually been introduced, which are the only practicable remedy; for the free space which must be left round the spindles for the spinner to see them play, is incompatible with any kind of fixed guard or parapluie.

There was before the late Factory Bill passed, a class of very young children employed in the flax mills, under the name of little doffers, forming generally a troop of from four to ten in each spinning-room, who, the moment they perceived the bobbins of any frame or side of a frame exhausted of roving, ran together, and furnished it with full ones as quickly as possible. They were not numerous in all, but they had an occupation requiring a great activity and attention. It was practised also in the fine spinning-rooms, which are perfectly free from dust; and, as it involved a kneeling and stooping position, seemed peculiarly appropriate to children, and is still done by them at a somewhat more advanced age.

The adjoining fig. 462. will serve to explain the mechanism by which the fine spinning of flax is performed. The front pair of drawing rollers represented at F, was at one time moistened by letting water trickle upon it, from a vessel B, furnished with a stopcock placed a little above, or by immersing one half of the under-roller in the water-trough as at A. The roller pair C, which receives the fine rovings from bobbins placed on skewers or upright pins in the creel behind, is so mounted as to be fixed at any desired distance from the front rollers F. This distance should be always a little more than the average length of the filaments of the line; for if it were equal to it, they would be seized at both ends by the two pairs of rollers, which move with different velocities, and would be torn asunder, instead of being drawn out alongside of each other. The front rollers indeed move in many such machines four times faster than the back pair. The rest of this flax-spinning apparatus resembles in every respect the throstle frame of the cotton-spinner. The thread, as it escapes from the front rollers, gets twisted by the spindle and flyer, and wound up in constant progression on the bobbin, the motion of the latter being retarded either by a washer of leather beneath its lower end, or sometimes, as shown in the figure, by a weighted lever H, suspended from a cord, which embraces the pulley-groove turned on the lower end of the bobbin. This friction of this cord on the pulley, which may be varied by changing the length of leverage at which the weight acts, gives the bobbin the requisite retardation for winding up the yarn.

The bobbin G, at the same time that it has this retarded movement of revolution on its axis, has another motion up and down on the spindle I, to present itself at different points to the thread, and to cause the equal distribution of this over the surface of the bobbin-barrel. This latter motion is given by a double eccentric L, which by turning slowly on its axis, makes the balance-lever M oscillate, and thereby raises or depresses the bobbin-rail with its row of spindles. N is a section of the long tin drum, which extends the whole breadth of the frame, and communicates its rotatory motion, derived from the steam-pulley, to the spindles, by the intervention of the endless cotton cords O, as also to the fluted rollers C, F, and to the axis of the heart-shaped or eccentric wheel L, working in an endless screw.

The ratio of the velocity of the rollers of supply C, with the front or delivering rollers F, and with the spindles, is proportional to the fineness of the yarn. For low numbers, the draught is usually fourfold. The speed of the spindles also varies with the quality of the yarn, according as it is intended for warp or weft; the former requiring more twist than the latter; but never so much as to cause it to snarl into a knot, when left free to turn on itself.

One of the most important improvements hitherto made in the spinning of flax is that for which James Kay, of Preston, obtained a patent in July, 1825. Its peculiar feature is the maceration in warm water of the slivers or rovings, previously to spinning them, by conducting them into tin cans, with open bottoms, fitted into circular boxes having holes like a cullender, and immersed into a trough of warm water. The slivers as they pass from the rollers are let fall through the cans into these boxes, when they are to be repeatedly pressed and beaten down by a plunger, or the action of rollers, as may be most convenient. The material must be thoroughly freed from air, and macerated. After five or six hours it is to be removed from the water, and placed in its compressed state at the back part of a drawing and spinning machine. The cake being now turned over, the end of the roving first deposited in the can is drawn out with care, then raised up, and passed over a tension roller to the drawing apparatus. The first pair of rollers for the drawing process merely retains the filaments; while at a distance of two inches and a half the drawing rollers are placed. Both are fluted for the purpose of taking firm hold of the material; and the drawing pair is made to move eight times quicker than the retaining. As the flax fibres have in this state little or no elasticity, and as they adhere loosely in their macerated condition, the drawing rollers must be placed thus close to the retaining rollers, and being made to move at a proper speed, produce an extremely attenuated thread.

The adjoining table represents, in three compartments, the most important rooms in a flax-mill, viz.:--

I. The tow preparing room.

II. The line preparing room for the long flax.

III. One room of spinning machines as a pattern for the rest.

A, lap machine; B, 4-feet breaker card; C, 3 feet 6 inches ditto; D, 3-feet finisher card, 3 workers; E, cut tow, second drawing, 5 heads; F, cut tow, first drawing, 4 heads; G, cut tow, reg. roving, 32 spindles; H, 4-feet breaker card; I, 4-feet finisher ditto; K, long tow, first drawing, 3 heads; L, long tow, second drawing, 4 heads; M, long tow, roving 4 spindles.

A, cut line, first drawing; B, cut line, second drawing, 4 heads; C, cut line, third drawing, 5 heads; D, cut line, reg. roving 32 spindles each; E, long line, first drawing; F, long line, second drawing, 3 heads each; G, long line, third drawing, 4 heads each; H, long line, roving 16 spindles.

I. The line preparing room comprehends:-- 1. Heckling machines with heckles. 2. Line spreaders, or first drawing slivers. 3. Frames for the second drawing, of 3 heads each. 4. Frames for the third drawing, of 4 heads each. 5. Roving frames of 16 spindles each. 6. Spare fallers for first drawing with gills. 7. Ditto ditto for second and third drawing with ditto. 8. Ditto ditto for roving.

II. The cut flax line preparing room:-- 1. Sets of heckling frames (excentric.) 2. Cutting or breaking machine. 3. Line spreaders or drawing ditto. 4. Frames for second drawing, 4 heads each. 5. Ditto third ditto, 5 ditto. 6. Ditto, regulator roving, 32 spindles each. 7. Spare fallers with gills for first drawing. 8. Ditto, ditto for second and third ditto. 9. Ditto, ditto, with gills for roving.

III. Long or uncut flax tow preparation:-- 1. Lap machine. 2. Breaker cards, 4 feet diameter. 3. Finisher ditto, ditto. 4. Frames for first drawing, 3 heads each. 5. Ditto for second drawing, 3 heads each. 6. Ditto for roving, 16 spindles each. 7. Spare fallers, with gills for first and second drawing. 8. Ditto, ditto, ditto, for roving.

IV. Cut flax tow preparation:-- 1. Lap machine. 2. First breaker cards, 4 feet diameter. 3. Second ditto, ditto, 3 feet 6 inches ditto. 4. Finisher cards with 8 workers. 5. First drawing frames, of 4 heads each. 6. Second ditto, ditto, of 5 ditto. 7. Frames for regulator roving, 32 spindles each frame. 8. Spare fallers with gills for first and second drawing. 9. Ditto, ditto, for roving.

V. Spinning rooms for both lines and tows:--spindles in frames in a number proportional to the number of the above preparation machines; and consequently to the quantity and quality of the flax yarn intended to be spun.

VI. Utensils and tools; such as cards clothing with needle pointed filleting.

Observations upon the above statement of the series of machinery requisite in a modern flax mill of the most improved construction:--

The long or uncut flax to be spun into yarns averaging 30 leas per lb.

Each heckling machine will produce about 4-1/2 cwts. per day, which would be distributed into 200 lbs. of line, and 266-2/3 of tow.

The total with 3 machines would be therefore 600 lbs. of line, and 800 lbs. of tow.

The preceding statement contains three systems of line preparing, each system being composed of--

1 line spreader, or first drawing; 1st frame of 3 heads; 2d ditto, 2 slivers each; 1 ditto of 4 ditto; 3d ditto, ditto ditto; 2 ditto rovings of 32 spindles, which are capable of supplying about 640 spinning ditto; 1 line spreader being allowed for contingencies.

The above statement contains 3 systems of tow (uncut) preparation, each system being composed of--

1 breaker card; 2 finisher ditto, 1 frame of first drawing, 3 heads of 4 slivers each; 1 ditto second ditto, 4 ditto, 4 ditto ditto; 2-1/3 ditto rovings or 37 spindles, which are capable of supplying about 660 spinning ditto; 1 lap machine being sufficient for 2 or 3 systems; 1 extra finisher is deemed desirable.

The statement contains 2 systems of heckling machines for cut flax, a system consisting of either 8 or 10 machines; for the coarser work, 8 machines in succession finer and finer, are sufficient; but for the finest 10 or 12 are required. Each system will produce between 2 and 300 lbs. per diem, of raw flax, heckled, divided on the average into 170 lbs. line, 280 lbs. tow, which will about equal the supply of the 5th system contained in the statement, each consisting of--

1 line spreader or 1st drawing; 1 frame 2d drawing; 4 heads 4 slivers each; 1 ditto 3d ditto, 5 ditto 4 ditto ditto; 1 ditto roving 32 spindles; and are capable of supplying about 480 ditto, of spinning.

The statement contains 2 systems of tow (cut flax) preparings, each system being composed of--

2 second breaker card; 4 finishers ditto; 4 frames 1st drawing, 4 heads each 4 slivers; 4 ditto 2d ditto, 5 ditto ditto, 4 ditto; 4 regulator rovings 128 spindles, and are capable to supply about 1800 spinning ditto. 1 first-breaker card and lap frame are sufficient to 2 or 3 systems.

Summary view:--

Long or uncut line 3 systems of 640 spindles = 1920 Ditto -- tow 3 ditto 660 ditto 1980 3900 ---- Cut -- line 5 ditto 480 ditto 2400 Ditto -- tow 2 ditto 1800 ditto 3600 6000 ---- ---- Total of spinning spindles 9900

3900 spindles, at an average of 30 leas yarn per lb., would turn off 9 leas per spindle per diem with waste circa 1400 lbs.

6000 spindles, at an average of 100 leas yarn per lb., would turn off 6 leas per spindle per diem with waste circa 450 lbs.

Yarns produced: £. s. d. Of average 30 leas per lb. per week circa 1050 boles at 9_s._ 472 10 0 Of ditto 100 ditto -- -- 1080 -- 486 0 0 ---- ---------- Total weekly produce 2130 958 10 0

£. s. d. Weekly charges, wages, &c. 150 0 0 Flax 400 0 0 Weekly expenses 40 0 0 Interest on 60,000_l._ } 120 0 0 10 per annum } 710 0 0 --------- ---------- Weekly profit 248 10 0

Measures of flax yarn; and statistics of the linen trade for the United Kingdom.

One lea of flax yarn at Leeds is = 300 yards. One spindle Scotch = 38 leas = 11400 yards. One rand = 6 ditto = 1800 ditto. One dozen is 12 rands = 72 ditto = 21600 ditto.

When yarn is estimated in Nos. it implies the number of leas in one pound weight; as in cotton, it means the number of hanks of 840 yards each in one pound.

Imports of flax and tow, or codilla of hemp and flax, at a duty of 1d. per cwt., in

1834. 1835. 1837. 1838. ------- ------- --------- --------- lbs. lbs. lbs. lbs. 811,722 740,814 1,529,116 1,002,256

Retained for consumption. 794,272 728,143 1,532,059 1,002,408

Linen yarn exported 2,611,215

Linen manufactures exported, including flax yarn, declared value _£_3,208,139 _£_3,645,097 _£_2,613,293

FLINT. (Pierre à fusil, Fr; Feuerstein, Germ.) The fracture of this fossil is perfectly conchoidal, sometimes glossy, and sometimes dull on the surface. It is very hard, but breaks easily, and affords very sharp-edged splintery fragments; whence it is a stone which strikes most copious sparks with steel. It is feebly translucid, has so fine and homogeneous a texture as to bear polishing, but possesses little lustre. Its colours are very various, but never vivid. The blackish-brown flint is that usually found in the white chalk. It is nearly black and opaque, loses its colour in the fire, and becomes grayish-white, and perfectly opaque. Flints occur almost always in nodules or tubercular concretions of various and very irregular forms. These nodules, distributed in strata among the chalk, alongside of one another and almost in contact, form extensive beds; interrupted, indeed, by a multitude of void spaces, so as to present, if freed from the earthy matter in which they are imbedded, a species of network with meshes, very irregular both in form and dimension.

The nodules of silex, especially those found in the chalk, are not always homogeneous and solid. Sometimes there is remarked an organic form towards their centre, as a madrepore or a shell, which seems to have served as their nucleus; occasionally the centre is hollow, and its sides are studded over with crystals of quartz, carbonate of iron, pyrites, concretionary silex or calcedony, filled with pulverulent silica nearly pure, or silex mixed with sulphur; a very singular circumstance.

Flints are observed to be generally humid when broken immediately after being dug out of the ground; a property which disappears after a short exposure to the air. When dried they become more brittle and more splintery, and sometimes their surfaces get covered at old fractures with a thin film or crust of opaque silex.

Flints calcined and ground to a powder enter into the composition of all sorts of fine pottery ware.

The next important application of this siliceous substance is in the formation of gun-flints, for which purpose it must be cut in a peculiar manner. The following characters distinguish good flint nodules from such as are less fit for being manufactured. The best are somewhat convex, approaching to globular; those which are very irregular, knobbed, branched and tuberose, are generally full of imperfections. Good nodules seldom weigh more than 20 pounds; when less than 2, they are not worth the working. They should have a greasy lustre, and be particularly smooth and fine grained. The colour may vary from honey-yellow to blackish-brown, but it should be uniform throughout the lump, and the translucency should be so great as to render letters legible through a slice about one-fiftieth of an inch thick, laid down upon the paper. The fracture should be perfectly smooth, uniform, and slightly conchoidal; the last property being essential to the cutting out of perfect gun-flints.

Four tools are employed by the gun-flint makers.

First, a hammer or mace of iron with a square head, from 1 to 2 pounds weight, with a handle 7 or 8 inches long. This tool is not made of steel, because so hard a metal would render the strokes too harsh, or dry as the workmen say, and would shatter the nodules irregularly, instead of cutting them with a clean conchoidal fracture.

Second, a hammer with 2 points, made of good steel well hardened, and weighing from 10 to 16 ounces, with a handle 7 inches long passing through it in such a way that the points of the hammer are nearer the hand of the workman than the centre of gravity of the mass.

Third, the disc hammer or roller, a small solid wheel, or flat segment of a cylinder, parallel to its base, only two inches and a third in diameter, and not more than 12 ounces in weight. It is formed of steel not hardened, and is fixed upon a handle 6 inches long, which passes through a square hole in its centre.

Fourth, a chisel tapering and bevelled at both extremities, 7 or 8 inches long, and 2 inches broad, made of steel not hardened; this is set on a block of wood, which serves also for a bench to the workmen. To these 4 tools a file must be added, for the purpose of restoring the edge of the chisel from time to time.

After selecting a good mass of flint, the workman executes the following four operations on it.

1. He breaks the block. Being seated upon the ground, he places the nodule of flint on his left thigh, and applies slight strokes with the square hammer to divide it into smaller pieces of about a pound and a half each, with broad surfaces and almost even fractures. The blows should be moderate, lest the lump crack and split in the wrong direction.

2. He cleaves or chips the flint. The principal point is to split the flint well, or to chip off scales of the length, thickness, and shape adapted for the subsequent formation of gun flints. Here the greatest dexterity and steadiness of manipulation are necessary; but the fracture of the flint is not restricted to any particular direction, for it may be chipped in all parts with equal facility.

The workman holds the lump of flint in his left hand, and strikes with the pointed hammer upon the edges of the great planes produced by the first breaking, whereby the white coating of the flint is removed in small scales, and the interior body of the flint is laid bare; after which he continues to detach similar scaly portions from the clean mass.

These scaly portions are nearly an inch and a half broad, two inches and a half long, and about one-sixth of an inch thick in the middle. They are slightly convex below, and consequently leave in the part of the lump from which they were separated a space slightly concave, longitudinally bordered by two somewhat projecting straight lines or ridges. The ridges produced by the separation of the first scales must naturally constitute nearly the middle of the subsequent pieces; and such scales alone as have their ridges thus placed in the middle are fit to be made into gun-flints. In this manner the workman continues to split or chip the mass of flint in various directions, until the defects usually found in the interior render it impossible to make the requisite fractures, or until the piece is too-much reduced to sustain the smart blows by which the flint is divided.

3. He fashions the gun-flints. Five different parts may be distinguished in a gun-flint. 1. The sloping facet or bevel part, which is impelled against the hammer of the lock. Its thickness should be from two to three twelfths of an inch; for if it were thicker it would be too liable to break; and if more obtuse, the scintillations would be less vivid. 2. The sides, or lateral edges, which are always somewhat irregular. 3. The back or thick part opposite the tapering edge. 4. The under surface, which is smooth and rather concave. And 5. The upper face, which has a small square plane between the tapering edge and the back, for entering into the upper claw of the cock.

In order to fashion the flint, those scales are selected which have at least one of the above mentioned longitudinal ridges; the workman fixes on one of the two tapering borders to form the striking edge, after which the two sides of the stone that are to form the lateral edges, as well as the part that is to form the back, are successively placed on the edge of the chisel in such a manner that the convex surface of the flint, which rests on the forefinger of the left hand, is turned towards that tool. Then with the disc hammer he applies some slight strokes to the flint just opposite the edge of the chisel underneath, and thereby breaks it exactly along the edge of the chisel.

4. The finishing operation is the trimming, or the process of giving the flint a smooth and equal edge; this is done by turning up the stone and placing the edge of its tapering end upon the chisel, in which position it is completed by 5 or 6 slight strokes of the disc hammer. The whole operation of making a gun-flint, which I have used so many words to describe, is performed in less than one minute. A good workman is able to manufacture 1000 good chips or scales in a day (if the flint-balls be of good quality), or 500 gun-flints. Hence, in the space of 3 days, he can easily cleave and finish 1000 gun-flints without any assistance.

A great quantity of refuse matter is left, for scarcely more than half the scales are good, and nearly half the mass in the best flints is incapable of being chipped out; so that it seldom happens that the largest nodules furnish more than 50 gun-flints.

Flints form excellent building materials; because they give a firm hold to the mortar by their irregularly rough surfaces, and resist, by their nature, every vicissitude of weather. The counties of Kent, Essex, Suffolk, and Norfolk contain many substantial specimens of flint-masonry.

FLOSS, of the puddling furnace, is the fluid glass floating upon the iron produced by the vitrification of the oxides and earths which are present.

FLOSS-SILK (Filoselle, Bourre de soie, or fleuret, Fr.); is the name given to the portions of ravelled silk broken off in the filature of the cocoons, which is carded like cotton or wool, and spun into a soft coarse yarn or thread, for making bands, shawls, socks, and other common silk fabrics. The floss or fleuret, as first obtained, must be steeped in water, and then subjected to pressure, in order to extract the gummy matter, which renders it too harsh and short for the spinning wheel. After being dried it is made still more pliant by working a little oil into it with the hands. It is now ready to be submitted to the carding engine. See COTTON MANUFACTURE. It is spun upon the flax wheel.

The female peasants of Lombardy generally wear clothes of homespun floss silk. Of late years, by improved processes, pretty fine fabrics of this material have been produced both in England and France. M. Ajac, of Lyons, presented at one of the French national exhibitions of the objects of industry, a great variety of scarfs and square shawls, of bourre de sole, closely resembling those of cachemere.

FLOUR; the finely ground meal of wheat, and of any other corns or cerealia. See BREAD.

FLOUR OF WHEAT, Adulterations of, to detect.

The first method is by specific gravity. If potato flour be added, which is frequently done in France, since a vessel which contains one pound of wheat flour will contain one pound and a half of the fecula, the proportion of this adulteration may be easily estimated. If gypsum or ground bones be mixed with the flour, they will not only increase its density still more; but they will remain after burning away the meal.

The second method is by ascertaining the quantity of gluten which the suspected sample will afford, by the process prescribed under the article BREAD. The two following chemical criteria may also be employed.

1st. Nitric acid has the property of colouring wheat flour of a fine orange yellow, whereas it affects the colour neither of fecula nor starch.

2nd. Pure muriatic acid colours good wheat flour of a deep violet, but dissolves fecula or starch, and forms with it a light, colourless, viscous fluid, decomposable by alkalis. It may also be observed, that as fecula absorbs less water than flour, this affords a ready means of detection.

The adulteration with bean or pea flour may be detected by pouring boiling water upon it, which developes the peculiar smell of these two substances.

FLOWERS (Fleurs, Fr.; Blumen, Germ.) of benzoin, of sulphur, of zinc, &c., is the appellation given by the older chemists to such substances as were obtained in a pulverulent or rather minutely crystalline form by the process of sublimation.

FLOWERS, ARTIFICIAL, MANUFACTURE OF. The art of representing by flowers, leaves, plants, &c., vegetable nature in her ornamental productions, constitutes the business of the artificial florist. The Italians appear to have been the first people in Europe who excelled in the art of making artificial flowers; but of late years the French have been most ingenious in this branch of industry.

Ribbons folded in different forms and of different colours were originally employed for imitating flowers, by being attached to wire stems. This imitation soon gave way to that by feathers, which are more delicate in texture, and more capable of assuming a variety of flower-like figures. But a great difficulty was encountered in dyeing them with due vivacity. The savages of South America manufacture perfect feather flowers, derived from the brilliant plumage of their birds, which closely resemble the products of vegetation. The blossoms and leaves are admirable, while the colours never fade.

The Italians employ frequently the cocoons of the silkworm for this purpose; these take a brilliant dye, preserve their colour, and possess a transparent velvety appearance, suitable for petals. Of late years, the French have adopted the finest cambric for making petals, and the taffeta of Florence for the leaves. M. de Bernardière employs whalebone in very thin leaves for artificial flowers; and by bleaching and dyeing them of various hues, he has succeeded in making his imitations of nature to be very remarkable.

The colouring matters used in flower dyeing are the following:--

For red; carmine dissolved in a solution of salt of tartar.

For blue; indigo dissolved in sulphuric acid, diluted and neutralized in part by Spanish whitening.

For bright yellow; a solution of turmeric in spirit of wine. Cream of tartar brightens all these colours.

For violet; archil, and a blue bath.

For lilac; archil.

Some petals are made of velvet, and are coloured merely by the application of the finger dipped in the dye.

FLUATES, more properly fluorides (Eng. and Fr.; Flusssäure, Germ.); compounds of fluorine and the metals; as fluor spar, for example, which consists of fluorine and calcium.

FLUOR SPAR. (Chaux fluatée, Fr.; Spath fluor, Germ.) This mineral often exhibits a variety of vivid colours. It crystallizes in the cubic system; with regular octahedral and tetrahedral cleavages; spec. grav. 3·1 to 3·2; scratches calc spar, but is scratched by a steel point; usually phosphorescent with heat; fusible at the blowpipe into an opaque bead; acted on by the acids, with disengagement of a vapour which corrodes glass; its solution affords precipitates with the oxalates, but not with ammonia. Its constituents are, fluorine, 48·13; calcium, 51·87 in 100.

Fluor spar occurs subordinate to metallic veins; as to those of lead, in Derbyshire; of tin, in Saxony and Bohemia; but it is found also in masses or veins, either in crystalline rocks, associated with quartz, heavy spar, &c., as in Auvergne, Forez, Vosges, Norberg in Sweden; Norway; Petersburg; near Hall; Gourock, in Scotland, &c.; or among secondary limestones, slates, and sandstones, in Derbyshire, Cumberland, Cornwall, and New Jersey. It exists also in the amygdaloids of Scotland, and in the volcanic products of Monte Somma at Vesuvius. The variously coloured specimens, called Derbyshire spar, are worked upon the turning lathe into vases and other ornamental objects.

FLUX, (Eng. and Fr.; Fluss, Germ.) signifies any substance capable of promoting the fusion of earths or metallic ores by heat. White flux is the residuum of the deflagration in a red hot crucible, of a mixture of two parts of nitre, and one of cream of tartar. It is in fact merely a carbonate of potash. Black flux is obtained when equal parts of nitre and tartar are deflagrated. It owes its colour to the carbonaceous matter of the tartaric acid, which remains unconsumed; the quantity of nitre being too small for that purpose. The presence of the charcoal renders this preparation a convenient flux for reducing calcined or oxidized ores to the metallic state. Limestone, fluor-spar, borax, and several earthy or metallic oxides are employed as fluxes in metallurgy.

FLY POWDER; the black coloured powder obtained by the spontaneous oxidizement of metallic arsenic in the air.

FODDER; is the name of a weight by which lead and some other metals are sold in this country. It varies in its amount in different parts of the kingdom; being in Northumberland estimated at 21 cwts., and in other counties 22, 23 or even more cwts.

FONDUS; is the name given by the French to a particular style of calico printing resembling the rainbow, in which the colours are graduated or melted (fondus) into one another, as in the prismatic spectrum. See PAPER HANGINGS, for a description of the process.

FORGE; (Eng. and Fr.; Feuer, Germ.) is the name either of the furnace, where wrought iron is hammered and fashioned with the aid of heat, or the great workshop where iron is made malleable. The former is called a smith’s forge, the latter a shingling mill. See IRON.

Fig. 466. represents a portable truck forge of a very commodious construction. A is the cylindric leather bellows, pressed down by a helical spring, and worked by means of the handle at B, which moves the horizontal shaft C, with its two attached semicircular levers and chains. D, is the pipe which conducts the blast to the nozzle at E. The hearth may be covered with a thin fire-tile or with cinders. F is a vice fixed to the strong rectangular frame. This apparatus answers all the ordinary purposes of a smith’s forge; and is peculiarly adapted to ships, and to the execution of engineering jobs upon railways, or in the country. The height is 2 feet 6 inches; the length is 2 feet 9 inches; the width 2 feet. Weight about 2 cwt.

FORMIATES; are compounds of formic acid, with the salifiable bases. Many of them are susceptible of crystallization.

FORMIC ACID; (Acide Formique, Fr.; Ameisensäure, Germ.) exists in the bodies of wood ants, associated with the malic or acid of apples. The artificial formation of this animal secretion, is one of the most remarkable triumphs of modern chemistry. If 10 parts of tartaric acid, 14 of black oxide of manganese, 15 of concentrated sulphuric acid, and from 20 to 30 of water be mixed and distilled in a retort, formic acid will be the liquid product; while carbonic acid will be disengaged. It may also be generated from other mixtures. This acid is transparent and colourless, of a pungent sour smell, a strongly acid taste, of specific gravity 1·1168 at 60° F., and may be re-distilled without suffering any change. It contains in its most concentrated form 19-3/4 per cent. of water. The dry acid, as it exists in the formiates, is composed of 32·54 carbon, 2·68 hydrogen, and 64·78 oxygen; or of two volumes carbonic oxide gas, and one volume of vapour of water. It reduces the oxides of mercury and silver to the metallic state. It has not hitherto been applied to any use in the arts.

FORMULÆ, CHEMICAL, are symbols representing the different substances, simple and compound.

+-------------------------+--------------------+---------+--------+ | Name. | Formula. | Oxygen |Hydrogen| | | | = 100. | = 1. | +-------------------------+--------------------+---------+--------+ |Oxygen |O | 100·000 | 16·026 | |Hydrogen |H | 6·2398| 1·000 | | |2H | 12·4796| 2·000 | |Nitrogen |N | 88·518 | 14·186 | | |2N | 177·086 | 28·372 | |Phosphorus |P | 196·155 | 31·436 | | |2P | 392·310 | 68·872 | |Chlorine |Cl | 221·325 | 35·470 | | |2Cl | 442·650 | 70·940 | |Iodine |I | 768·781 |123·206 | | |2I |1537·562 |246·412 | |Carbon |C | 76·437 | 12·250 | | |2C | 152·875 | 24·500 | |Boron |B | 135·983 | 21·793 | | |2B | 271·966 | 43·586 | |Silicon |Si | 277·478 | 44·469 | |Selenium |Se | 494·582 | 79·263 | |Arsenic |As | 470·042 | 75·329 | | |2As | 940·084 |150·659 | |Chromium |Cr | 351·819 | 56·383 | | |2Cr | 703·638 |112·766 | |Molybdenum |Mo | 598·525 | 95·920 | |Tungstenium |Tu or W |1183·200 |189·621 | |Antimony |Sb | 806·452 |129·243 | | |2Sb |1612·904 |258·486 | |Tellurium |Te | 806·452 |129·243 | |Tantalum |Ta |1153·715 |184·896 | | |2Ta |2307·430 |369·792 | |Titanium |Ti | 389·092 | 62·356 | |Gold (aurum) |Au |1243·013 |199·207 | | |2Au |2486·026 |398·415 | |Platina |Pt |1215·220 |194·753 | |Rhodium |R | 750·680 |120·305 | | |2R |1501·360 |240·610 | |Palladium |Pd | 714·618 |114·526 | |Silver (argentum) |Ag |1351·607 |216·611 | |Mercury (hydrargyrus) |Hg |1265·822 |202·863 | | |2Hg |2531·645 |405·725 | |Copper (cuprum) |Cu | 395·695 | 63·415 | | |2Cu | 791·390 |126·829 | |Uranium |U |2711·360 |434·527 | | |2U |5422·720 |869·154 | |Bismuth |Bi |1330·376 |213·208 | | |2Bi |2660·752 |426·416 | |Tin (stannum) |Sn | 735·294 |117·839 | |Lead (plumbum) |Pb |1294·498 |207·458 | | |2Pb |2588·996 |414·917 | |Cadmium |Cd | 696·767 |111·665 | |Zinc |Zn | 403·226 | 64·621 | |Nickel |Ni | 369·675 | 59·245 | |Cobalt |Co | 368·991 | 59·135 | | |2Co | 737·982 |118·270 | |Iron (ferrum) |Fe | 339·213 | 54·363 | | |2Fe | 678·426 |108·725 | |Manganese |Mn | 355·787 | 57·019 | | |2Mn | 711·575 |114·038 | |Cerium |Ce | 574·718 | 92·105 | | |2Ce |1149·436 |184·210 | |Zirconium |Zr | 420·238 | 67·348 | | |2Zr | 840·476 |134·696 | |Yttrium |Y | 401·840 | 64·395 | |Beryllium (glucinum) |Be | 331·479 | 53·123 | | |2Be | 662·958 |106·247 | |Aluminum |Al | 171·167 | 27·431 | | |2Al | 342·234 | 54·863 | |Magnesium |Mg | 158·353 | 25·378 | |Calcium |Ca | 256·019 | 41·030 | |Strontium |Sr | 547·285 | 87·709 | |Baryum |Ba | 856·88 |137·325 | |Lithium |L | 127·757 | 20·474 | |Natrium (sodium) |Na | 290·897 | 46·620 | | |2Na | 581·794 | 93·239 | |Kalium (potassium) |K | 489·916 | 78·515 | |Ammonia |2N2H³ | 214·474 | 34·372 | |Cyanogen |2NC | 329·911 | 52·872 | |Sulphuretted hydrogen |2HS | 213·644 | 34·239 | |Hydrochloric acid |2HCl | 455·129 | 72·940 | |Hydrocyanic acid |2HNC | 342·390 | 54·872 | | |. | | | |Water |2H | 112·479 | 18·026 | | |. | | | |Protoxide of nitrogen |2N | 277·036 | 44·398 | | |. | | | |Deutoxide of nitrogen |N | 188·518 | 30·212 | | |... | | | |Nitrous acid |2N | 477·036 | 76·449 | | |..... | | | |Nitric acid | 2N | 677·036 |108·503 | | |. | | | |Hyposulphurous acid |S | 301·165 | 48·265 | | |.. | | | |Sulphurous acid |S | 401·165 | 64·291 | | |..... | | | |Hyposulphuric acid | 2S | 902·330 |144·609 | | |... | | | |Sulphuric acid | S | 501·165 | 80·317 | | |..... | | | |Phosphoric acid | 2P | 892·310 |143·003 | | |..... | | | |Chloric acid | 2Cl | 942·650 |151·071 | | |...... | | | |Perchloric acid | 2Cl |1042·650 |167·097 | | |..... | | | |Iodic acid | 2I |2037·562 |326·543 | | |.. | | | |Carbonic acid |C | 276·437 | 44·302 | | |... | | | |Oxalic acid |2C | 452·875 | 72·578 | | |...... | | | |Boracic acid | 2B | 871·966 |139·743 | | |... | | | |Silicic acid |Si | 577·478 | 92·548 | | |.. | | | |Selenic acid |Se | 694·582 |111·315 | | |..... | | | |Arsenic acid | 2As |1440·084 |230·790 | | |... | | | |Protoxide of chrome |2Cr |1003·638 |160·840 | | |... | | | |Chromic acid |Cr | 651·819 |104·462 | | |... | | | |Molybdic acid |Mo | 898·525 |143·999 | | |... | | | |Tungstic, or wolfram acid| W |1483·200 |237·700 | | |... | | | |Oxide of antimony |2Sb |1912·904 |306·565 | | |.. | | | |Antimonious acid |Sb |1006·452 |161·296 | | |.... | | | | |2Sb |2012·904 |322·591 | | |..... | | | |Antimonic acid |2Sb |2112·904 |338·617 | | |.. | | | |Oxide of tellurium |Te |1006·452 |161·296 | | |... | | | |Tantalic acid |2Ta |2607·430 |417·871 | | |.. | | | |Titanic acid |Ti | 589·092 | 94·409 | | | . | | | |Protoxide of gold |2Au |2586·026 |414·441 | | |... | | | |Peroxide of gold |2Au |2786·026 |446·493 | | |.. | | | |Oxide of platina |Pt |1415·220 |226·086 | | |... | | | |Oxide of rhodium |2R |1801·360 |228·689 | | |. | | | |Oxide of palladium |Pd | 814·618 |130·552 | | |. | | | |Oxide of silver |Ag |1451·607 |232·637 | | | . | | | |Protoxide of mercury |2Hg |2631·645 |421·752 | | |. | | | |Peroxide of mercury |Hg |1365·822 |218·889 | | | . | | | |Protoxide of copper |2Cu | 801·390 |142·856 | | |. | | | |Peroxide of copper |Cu | 495·695 | 79·441 | | |. | | | |Protoxide of uranium |U |2811·360 |450·553 | | |... | | | |Peroxide of uranium |2U |5722·720 |917·132 | | |... | | | |Oxide of bismuth |2Bi |2960·752 |474·49 | | |. | | | |Protoxide of tin |Sn | 835·294 |133·866 | | |.. | | | |Peroxide of tin |Sn | 935·294 |149·892 | | |. | | | |Oxide of lead |Pb |1394·498 |223·484 | | |... | | | |Minium |2Pb |2888·996 |462·995 | | |.. | | | |Brown oxide of lead |Pb |1494·498 |239·511 | | |. | | | |Oxide of cadmium |Cd | 796·767 |127·691 | | |. | | | |Oxide of zinc |Zn | 503·226 | 80·649 | | |. | | | |Oxide of nickel |Ni | 469·675 | 75·271 | | |. | | | |Oxide of cobalt |Co | 468·991 | 75·161 | | |... | | | |Peroxide of cobalt |2Co |1037·982 |166·349 | | |. | | | |Protoxide of iron |Fe | 439·213 | 70·389 | | |... | | | |Peroxide of iron |2Fe | 978·426 |156·804 | | |. | | | |Protoxide of manganese |Mn | 455·787 | 73·045 | | |... | | | |Oxide of manganese |2Mn |1011·575 |162·117 | | |.. | | | |Peroxide of manganese |Mn | 555·787 | 89·071 | | |..... | | | |Manganesic acid | 2Mn |1211·575 |194·169 | | |. | | | |Protoxide of cerium |Ce | 674·718 |108·132 | | |... | | | |Oxide of cerium |2Ce |1449·436 |232·289 | | |... | | | |Zirconia |2Zr |1140·476 |182·775 | | |. | | | |Yttria |Y | 501·840 | 80·425 | | |... | | | |Glucina, or berryllia |2Be | 962·958 |154·325 | | |... | | | |Alumina |2Al | 642·334 |109·942 | | |. | | | |Magnesia |Mg | 258·353 | 41·404 | | |. | | | |Lime |Ca | 356·019 | 57·056 | | |. | | | |Strontia |Sr | 647·285 |103·735 | | |. | | | |Baryta |Ba | 956·880 |153·351 | | |. | | | |Lithia |L | 227·757 | 36·501 | | |. | | | |Natron, or soda |Na | 390·897 | 62·646 | | |... | | | |Peroxide of sodium |2Na | 881·794 |141·318 | | |. | | | |Kali, or potassa |K | 589·916 | 94·541 | | |... | | | |Peroxide of potassium | K | 789·916 |126·593 | | |. ... | | | |Sulphate of potassa |K S |1091·081 |174·859 | | |. ... | | | |Protosulphate of iron |Fe S | 940·378 |150·706 | | |... ... | | | |Persulphate of iron |2Fe S³ |2481·906 |397·754 | |Protochloride of iron |Fe 2Cl | 781·863 |125·303 | |Perchloride of iron |2Fe 2Cl³ |2006·376 |321·545 | |Protochloride of mercury |2Hg 2Cl |2974·295 |476·666 | |Perchloride of mercury |Hg 2Cl |1708·472 |273·803 | |Ferrocyanide of iron |Fe2NC + 2K2NC |2308·778 |370·008 | | |. ... ... ... .| | | |Alum |K S + 2AlS³ + 24 2H|5936·406 |951·378 | | |. ... ... ... | | | |Felspar |K Si + 2Al Si³ |3542·162 |567·673 | +-------------------------+--------------------+---------+--------+

FOUNDING of metals, chiefly of Iron. The operations of an iron foundry consist in re-melting the pig-iron of the blast furnaces, and giving it an endless variety of forms, by casting it in moulds of different kinds, prepared in appropriate manners. Coke is the only kind of fuel employed to effect the fusion of the cast iron.

The essential parts of a well-mounted iron foundry, are,

1. Magazines for pig irons of different qualities, which are to be mixed in certain proportions, for producing castings of peculiar qualities; as also for coal, coke, sands, clay, powdered charcoal, and cow-hair for giving tenacity to the loam mouldings.

2. One or more coke ovens.

3. A workshop for preparing the patterns and materials of the moulds. It should contain small edge millstones for grinding and mixing the loam, and another mill for grinding coal and charcoal.

4. A vast area, called properly the foundry, in which the moulds are made and filled with the melted metal. These moulds are in general very heavy, consisting of two parts at least, which must be separated, turned upside down several times, and replaced very exactly upon one another. The casting is generally effected by means of large ladles or pots, in which the melted iron is transported from the cupola, where it is fused. Hence the foundry ought to be provided with cranes, having jibs movable in every direction.

5. A stove in which such moulds may be readily introduced, as require to be entirely deprived of humidity, and where a strong heat may be uniformly maintained.

6. Both blast and air furnaces, capable of melting speedily the quantity of cast-iron to be employed each day.

7. A blowing machine to urge the fusion in the furnaces.

Fig. 467. represents the general plan of a well-mounted foundry.

a, is a cupola furnace of which the section and view will be afterwards given; it is capable of containing 5 tons of cast-iron.

a´, is a similar furnace, but of smaller dimensions, for bringing down 1-3/4 tons.

a´´, is a furnace like the first, in reserve for great castings.

b, b, b, b, a vast foundry apartment, whose floor to a yard in depth, is formed of sand and charcoal powder, which have already been used for castings, and are ready for heaping up into a substratum, or to be scooped out when depth is wanted for the moulds. There are besides several cylindrical pits, from five to seven yards in depth, placed near the furnaces. They are lined with brick work, and are usually left full of moulding sand. They are emptied in order to receive large moulds, care being had that their top is always below the orifice from which the melted metal is tapped.

These moulds, and the ladles full of melted metal are lifted and transported by the arm of one or more men, when their weight is moderate; but if it be considerable, they are moved about by cranes whose vertical shafts are placed at c, d, e, in correspondence, so that they may upon occasion transfer the load from one to another. Each crane is composed principally of an upright shaft, embraced at top by a collet, and turning below upon a pivot in a step; next of a horizontal beam, stretched out from nearly the top of the former, with an oblique stay running downwards, like that of a gallows. The horizontal beam supports a movable carriage, to which the tackle is suspended for raising the weights. This carriage is made to glide backwards or forwards along the beam by means of a simple rack and pinion mechanism, whose long handle descends within reach of the workman’s hand.

By these arrangements in the play of the three cranes, masses weighing five tons may be transported and laid down with the greatest precision upon any point whatever in the interior of the three circles traced upon fig. 467. with the points c, d, e, as centres.

c, d, e, are the steps, upon which the upright shafts of the three cranes rest and turn. Each shaft is 16 feet high.

f, f, is the drying stove, having its floor upon a level with that of the foundry.

f´, f´, is a supplementary stove for small articles.

g, g, g, are the coaking ovens.

h, is the blowing machine or fan.

i, is the steam-engine, for driving the fan, the loam-edge stones,

k, and the charcoal mill.

i´´, are the boiler and the furnace of the engine.

k´, workshop for preparing the loam and other materials of moulding.

l, is the apartment for the patterns.

The pig-iron, coals, &c. are placed either under sheds or in the open air, round the above buildings; where are also a smith’s forge, a carpenter’s shop, and an apartment mounted with vices for chipping and rough cleaning the castings by chisels and files.

Such a foundry may be erected upon a square surface of about 80 yards in each side, and will be capable, by casting in the afternoon and evening of each day, partly in large and partly in small pieces, of turning out from 700 to 800 tons per annum, with an establishment of 100 operatives, including some moulding boys.

Of making the Moulds.--1. Each mould ought to present the exact form of its object.

2. It should have such solidity that the melted metal may be poured into it, and fill it entirely without altering its shape in any point.

3. The air which occupies the vacant spaces in it, as well as the carburetted gases generated by the heat, must have a ready vent; for if they are but partially confined, they expand by the heat, and may crack, even blow up the moulds, or at any rate become dispersed through the metal, making it vesicular and unsound.

There are three distinct methods of making the moulds:--

1. In green sand; 2. In baked sand; 3. In loam.

To enumerate the different means employed to make every sort of mould exceeds the limits prescribed to this work. I shall merely indicate for each species of moulding, what is common to all the operations; and I shall then describe the fabrication of a few such moulds as appear most proper to give general views of this peculiar art.

Moulding in green sand.--The name green is given to a mixture of the sand as it comes from its native bed, with about one twelfth its bulk of coal reduced to powder, and damped in such a manner as to form a porous compound, capable of preserving the forms of the objects impressed upon it. This sand ought to be slightly argillaceous, with particles not exceeding a pin’s head in size. When this mixture has once served for a mould, and been filled with metal, it cannot be employed again except for the coarsest castings, and is generally used for filling up the bottoms of fresh moulds.

For moulding any piece in green sand, an exact pattern of the object must be prepared in wood or metal; the latter being preferable, as not liable to warping, swelling, or shrinkage.

A couple of iron frames form a case or box, which serves as an envelope to the mould. Such boxes constitute an essential and very expensive part of the furniture of a foundry. It is a rectangular frame, without bottom or lid, whose two largest sides are united by a series of cross bars, parallel to each other, and placed from 6 to 8 inches apart.

The two halves of the box carry ears corresponding exactly with one another; of which one set is pierced with holes, but the other has points which enter truly into these holes, and may be made fast in them by cross pins or wedges, so that the pair becomes one solid body. Within this frame there is abundance of room for containing the pattern of the piece to be moulded with its encasing sand, which being rammed into the frame, is retained by friction against the lateral faces and cross bars of the mould.

When a mould is to be formed, a box of suitable dimensions is taken asunder, and each half, No. 1. and No. 2., is laid upon the floor of the foundry. Green sand is thrown with a shovel into No. 1. so as to fill it; when it is gently pressed in with a rammer. The object of this operation is to form a plane surface upon which to lay in the pattern with a slight degree of pressure, varying with its shape. No. 1. being covered with sand, the frame No. 2. is laid upon it, so as to form the box. No. 2. being now filled carefully with the green sand, the box is inverted, so as to place No. 1. uppermost, which is then detached and lifted off in a truly vertical position; carrying with it the body of sand formed at the commencement of the operation. The pattern remains imbedded in the sand of No. 2., which has been exactly moulded upon a great portion of its surface. The moulder condenses the sand in the parts nearest to the pattern, by sprinkling a little water upon it, and trimming the ill-shaped parts with small iron trowels of different kinds. He then dusts a little well-dried finely-sifted sand over all the visible surface of the pattern, and of the sand surrounding it; this is done to prevent adhesion when he replaces the frame No. 1.

He next destroys the preparatory smooth bed or area formed in this frame, covers the pattern with green sand, replaces the frame 1. upon 2. to reproduce the box, and proceeds to fill and ram No. 1., as he had previously done No. 2. The object of this operation is to obtain very exactly a concavity in the frame No. 1., having the shape of the part of the model impressed coarsely upon the surface formed at the beginning, and which was meant merely to support the pattern and the sand sprinkled over it, till it got imbedded in No. 2.

The two frames in their last position, along with their sand, may be compared to a box of which No. 1. is the lid, and whose interior is adjusted exactly upon the enclosed pattern.

If we open this box, and after taking out the pattern, close its two halves again, then pour in melted metal till it fill every void space, and become solid, we shall obviously attain the wished-for end, and produce a piece of cast iron similar to the pattern. But many precautions must still be taken before we can hit this point. We must first lead through the mass of sand in the frame No. 1., one or more channels for the introduction of the melted metal; and though one may suffice for this purpose, another must be made for letting the air escape. The metal is run in by several orifices at once, when the piece has considerable surface, but little thickness, so that it may reach the remotest points sufficiently hot and liquid.

The parts of the mould near the pattern must likewise be pierced with small holes, by means of wires traversing the whole body of the sand, in order to render the mould more porous, and to facilitate the escape of the air and the gases. Then, before lifting off the frame No. 1., we must tap the pattern slightly, otherwise the sand enclosing it would stick to it in several points, and the operation would not succeed. These gentle jolts are given by means of one or more pieces of iron wire which have been screwed vertically into the pattern before finally ramming the sand into the frame No. 1., or which enter merely into holes in the pattern. These pieces are sufficiently long to pass out through the sand when the box is filled; and it is upon their upper ends that the horizontal blows of the hammer are given; their force being regulated by the weight and magnitude of the pattern. These rods are then removed by drawing them straight out; after which the frame No. 1. may be lifted off smoothly from the pattern.

The pattern itself is taken out, by lifting it in all its parts at once, by means of screw pins adjusted at the moment. This manœuvre is executed, for large pieces, almost always by several men, who while they lift the pattern with one hand, strike it with the other with small repeated blows to detach the sand entirely, in which it is generally more engaged than it was in that of the frame No. 1. But in spite of all these precautions, there are always some degradations in one or other of the two parts of the mould; which are immediately repaired by the workman with damp sand, which he applies and presses gently with his trowel, so as to restore the injured forms.

Hitherto I have supposed all the sand rammed into the box to be of one kind; but from economy, the green sand is used only to form the portion of the mould next the pattern, in a stratum of about an inch thick; the rest of the surrounding space is filled with the sand of the floor which has been used in former castings. The interior layer round the pattern is called in this case, new sand.

It may happen that the pattern is too complex to be taken out without damaging the mould, by two frames alone; then 3 or more are mutually adjusted to form the box.

When the mould, taken asunder into two or more parts, has been properly repaired, its interior surface must be dusted over with wood charcoal reduced to a very fine powder, and tied up in a small linen bag, which is shaken by hand. The charcoal is thus sifted at the moment of application, and sticks to the whole surface which has been previously damped a little. It is afterwards polished with a fine trowel. Sometimes, in order to avoid using too much charcoal, the surfaces are finally dusted over with sand, very finely pulverized, from a bag like the charcoal. The two frames are now replaced with great exactness, made fast together by the ears, with wedged bolts laid truly level, or at the requisite slope, and loaded with considerable weights. When the casting is large, the charcoal dusting as well as that of fine sand, is suppressed. Every thing is now ready for the introduction of the fused metal.

Moulding in baked or used sand.--The mechanical part of this process is the same as of the preceding. But when the castings are large, and especially if they are tall, the hydrostatic pressure of the melted metal upon the sides of the mould cannot be counteracted by the force of cohesion which the sand acquires by ramming. We must in that case adapt to each of these frames a solid side, pierced with numerous small holes to give issue to the gases. This does not form one body with the rest of the frame, but is attached extemporaneously to it by bars and wedged bolts. In general no ground coal is mixed with this sand. Whenever the mould is finished, it is transferred to the drying stove, where it may remain from 12 to 24 hours at most, till it be deprived of all its humidity. The sand is then said to be baked, or annealed. The experienced moulder knows how to mix the different sands placed at his disposal, so that the mass of the mould as it comes out of the stove, may preserve its form, and be sufficiently porous. Such moulds allow the gases to pass through them much more readily than those made of green sand; and in general the castings they turn out are less vesicular, and smoother upon the surface. Sometimes in a large piece, the three kinds of moulding, that in green sand, in baked sand, and in loam, are combined to produce the best result.

Moulding in loam.--This kind of work is executed from drawings of the pieces to be moulded, without being at the expense of making patterns. The mould is formed of a pasty mixture of clay, water, sand, and cow’s hair, or other cheap filamentous matter, kneaded together in what is called the loam mill. The proportions of the ingredients are varied to suit the nature of the casting. When the paste requires to be made very light, horse dung or chopped straw is added to it.

I shall illustrate the mode of fabricating loam moulds, by a simple case, such as that of a sugar pan. Fig. 468. is the pan. There is laid upon the floor of the foundry, an annular platform of cast-iron a b, fig. 469.; and upon its centre c, rests the lower extremity of a vertical shaft, adjusted so as to turn freely upon itself, while it makes a wooden pattern e f, fig. 470., describe a surface of revolution identical with the internal surface reversed of the boiler intended to be made. The outline e g, of the pattern is fashioned so as to describe the surface of the edge of the vessel. Upon the part a d b d, fig. 469., of the flat cast-iron ring, there must next be constructed, with bricks laid either flat or on their edge, and clay, a kind of dome, h i k, fig. 470., from two to four inches thick, according to the size and weight of the piece to be moulded. The external surface of the brick dome ought to be everywhere two inches distant at least, from the surface described by the arc e, f. Before building up the dome to the point i, coals are to be placed in its inside upon the floor, which may be afterwards kindled for drying the mould. The top is then formed, leaving at i, round the upright shaft of revolution, only a very small outlet. This aperture, as also some others left under the edges of the iron ring, enable the moulder to light the fire when it becomes necessary, and to graduate it so as to make it last long enough without needing more fuel, till the mould be quite finished and dry. The combustion should be always extremely slow.

Over the brick dome a pasty layer of loam is applied, and rounded with the mould g e f; this surface is then coated with a much smoother loam, by means of the concave edge of the same mould. Upon the latter surface, the inside of the sugar pan is cast; the line e g having traced, in its revolution, a ledge m. The fire is now kindled, and as the surface of the mould becomes dry, it is painted over by a brush, with a mixture of water, charcoal powder, and a little clay, in order to prevent adhesion between the surface already dried and the coats of clay about to be applied to it. The board g e f is now removed, and replaced by another, g´ e´ f´, fig. 471., whose edge e´ f´ describes the outer surface of the pan. Over the surface e, f, a layer of loam is applied, which is turned and polished so as to produce the surface of revolution e´ f´, as was done for the surface e f; only in the latter case, the line e´ g´ of the board does not form a new shoulder, but rubs lightly against m.

The layer of loam included between the two surfaces e f, e´ f´, is an exact representation of the sugar pan. When this layer is well dried by the heat of the interior fire, it must be painted like the former. The upright shaft is now removed, leaving the small vent hole through which it passed to promote the complete combustion of the coal. There must be now laid horizontally upon the ears of the platform d d, fig. 469., another annular platform p q, like the former, but a little larger, and without any cross-bar.

The relative position of these two platforms is shown in fig. 473. Upon the surface e´ f´, fig. 472., a new layer of loam is laid, two inches thick, of which the surface is smoothed by hand. Then upon the platform p q, fig. 473., a brick vault is constructed, whose inner surface is applied to the layer of loam. This contracts a strong adherence with the bricks which absorb a part of its moisture, while the coat of paint spread over the surface e´ f´, prevents it from sticking to the preceding layers of loam. The brick dome ought to be built solidly.

The whole mass is now to be thoroughly dried by the continuance of the fire, the draught of which is supported by a small vent left in the upper part of the new dome; and when all is properly dry, the two iron platforms are adjusted to each other by pin points, and p q is lifted off, taking care to keep it in a horizontal position. Upon this platform are removed the last brick dome, and the layer of loam which had been applied next to it; the latter of which represents exactly by its inside the mould of the surface e´ f´, that is of the outside of the pan. The crust contained between e f and e´ f´ is broken away, an operation easily done without injury to the surface e f, which represents exactly the inner surface of the pan; or only to the shoulder m, corresponding to the edge of the vessel. The top aperture through which the upright shaft passed must be now closed; only the one is kept open in the portion of the mould lifted off upon p q; because through this opening the melted metal is to be poured in the process of casting. The two platforms being replaced above each other very exactly, by means of the adjusting pin-points, the mould is completely formed, and ready for the reception of the metal.

When the object to be moulded presents more complicated forms than the one now chosen for the sake of illustration, it is always by analogous processes that the workman constructs his loam moulds, but his sagacity must hit upon modes of executing many things which at first sight appear to be scarcely possible. Thus, when the forms of the interior and exterior do not permit the mould to be separated in two pieces, it is divided into several, which are nicely fitted with adjusting pins. More than two cast-iron rings or platforms are sometimes necessary. When ovals or angular surfaces must be traced instead of those of revolution, no upright shaft is used, but wooden or cast-iron guides made on purpose, along which the pattern cut-out board is slid according to the drawing of the piece. Iron wires and claws are often interspersed through the brick work to give it cohesion. The core, kernel, or inner mould of a hollow casting is frequently fitted in when the outer shell is moulded. I shall illustrate this matter in the case of a gas-light retort, fig. 474. The core of the retort ought to have the form e e e e, and be very solid, since it cannot be fixed in the outer mould, for the casting, except in the part standing out of the retort towards m m. It must be modelled in loam, upon a piece of cast-iron called a lantern, made expressly for this purpose. The lantern is a cylinder or a truncated hollow cone of cast iron, about half an inch thick; and differently shaped for every different core. The surface is perforated with holes of about half an inch in diameter. It is mounted by means of iron cross bars, upon an iron axis, which traverses it in the direction of its length. Fig. 475. represents a horizontal section through the axis of the core; g h is the axis of the lantern, figured itself at i k k i; o i i o is a kind of disc or dish, perpendicular to the axis, open at i i, forming one piece with the lantern, whose circumference o o presents a curve similar to the section of the core, made at right angles to its axis. We shall see presently the two uses for which this dish is intended. The axis g h is laid upon two gudgeons, and handles are placed at each of its extremities, to facilitate the operation in making the core. Upon the whole surface of the lantern, from the point h to the collet formed by the dish, a hay cord as thick as the finger is wound. Even two or more coils may be applied, as occasion requires, over which loam is spread to the exact form of the core, by applying with the hand a board, against the dish o o, with its edge cut out to the desired shape; as also against another dish, adjusted at the time towards h; while by means of the handles a rotatory movement is given to the whole apparatus.

The hay interposed between the lantern and the loam, which represents the crust of the core, aids the adhesion of the clay with the cast iron of the lantern, and gives passage to the holes in its surface, for the air to escape through in the casting.

When the core is finished, and has been put into the drying stove, the axis g h is taken out, then the small opening which it leaves at the point h, is plugged with clay. This is done by supporting the core by the edges of the dish, in a vertical position. It is now ready to be introduced into the hollow mould of the piece.

This mould executed in baked sand consists of three pieces, two of which absolutely similar, are represented, fig. 476., at p q, the third is shown at r s. The two similar parts p q, present each the longitudinal half of the nearly cylindrical portion of the outer surface of the gas retort; so that when they are brought together, the cylinder is formed; r s contains in its cavity the kind of hemisphere which forms the bottom of the retort. Hence, by adding this part of the mould to the end of the two others, the resulting apparatus presents in its interior, the exact mould of the outside of the retort; an empty cylindrical portion t t, whose axis is the same as that of the cylinder u u, and whose surface, if prolonged, would be every where distant from the surface u u, by a quantity equal to the desired thickness of the retort. The diameter of the cylinder t t is precisely equal to that of the core, which is slightly conical, in order that it may enter easily into this aperture t t, and close it very exactly when it is introduced to the collet or neck.

The three parts of the mould and the core being prepared, the two pieces p q, must first be united, and supported in an upright position; then the core must be let down into the opening t t, fig. 477. When the plate or disc o o of the core is supported upon the mould, we must see that the end of the core is every where equally distant from the edge of the external surface u u, and that it does not go too far beyond the line q q. Should there be an inaccuracy, we must correct it by slender iron slips placed under the edge of the disc o o; then by means of a cast iron cross, and screw bolts v v, we fix the core immovably. The whole apparatus is now set down upon r s, and we fix with screw bolts the plane surface q q upon r r; then introduce the melted metal by an aperture z, which has been left at the upper part of the mould.

When, instead of the example now selected, the core of the piece to be cast must go beyond the mould of the external surface, as is the case with a pipe open at each end, the thing is more simple, because we may easily adjust and fix the core by its two ends.

In casting a retort, the metal is poured into the mould set upright. It is important to maintain this position in the two last examples of casting; for all the foreign matters which may soil the metal during its flow, as the sand, the charcoal, gases, scoriæ, being less dense than it, rise constantly to the surface. The hydrostatic pressure produced by a high gate, or filling-in aperture, contributes much to secure the soundness and solidity of the casting. This gate piece being superfluous, is knocked off almost immediately after, or even before the casting cools. Very long, and somewhat slender pieces, are usually cast in moulds set up obliquely to the horizon. As the metal shrinks in cooling, the mould should always be somewhat larger than the object intended to be cast. The iron founder reckons in general upon a linear shrinkage of a ninety-sixth part; that is one-eighth of an inch per foot.

Melting of the cast-iron.--The metal is usually melted in a cupola furnace, of which the dimensions are very various. Fig. 478. represents in plan, section, and elevation, one of these furnaces of the largest size; being capable of founding 5 tons of cast-iron at a time. It is kindled by laying a few chips of wood upon its bottom, leaving the orifice c open, and it is then filled up to the throat with coke. The fire is lit at c, and in a quarter or half an hour, when the body of fuel is sufficiently kindled, the tuyère blast is set in action. The flame issues then by the mouth as well as the orifice c, which has been left open on purpose to consolidate it by the heat. Without this precaution, the sides which are made up in argillaceous sand after each day’s work, would not present the necessary resistance. A quarter of an hour afterwards, the orifice c is closed with a lump of moist clay, and sometimes, when the furnace is to contain a great body of melted metal, the clay is supported by means of a small plate of cast-iron fixed against the furnace. Before the blowing machine is set a going, the openings g g g had been kept shut. Those of them wanted for the tuyères are opened in succession, beginning at the lowest, the tuyères being raised according as the level of the fused iron stands higher in the furnace. The same cupola may receive at a time from one to six tuyères, through which the wind is propelled by the centrifugal action of an excentric fan or ventilator. It does not appear to be ascertained whether there be any advantage in placing more than two tuyères facing each other upon opposite sides of the furnace. Their diameter at the nozzle varies from 3 to 5 inches. They are either cylindrical or slightly conical. A few minutes after the tuyères have begun to blow, when the coke sinks in the furnace, alternate charges of coke and pig iron must be thrown in. The metal begins to melt in about 20 minutes after its introduction; and successive charges are then made every 10 minutes nearly; each charge containing from 2 cwt. to 5 cwt. of iron, and a quantity proportional to the estimate given below. The amount of the charges varies of course with the size of the furnace, and the speed required for the operation. The pigs must be previously broken into pieces weighing at most 14 or 16 pounds. The vanes of the blowing fan make from 625 to 650 turns per minute. The two cupolas represented fig. 478., and another alongside in the plan, may easily melt 6-1/2 tons of metal in 2-3/4 hours; that is 2-1/3 tons per hour. This result is three or four times greater than what was formerly obtained in similar cupolas, when the blast was thrown in from small nozzles with cylinder bellows, moved by a steam engine of 10 horses power.

In the course of a year, a considerable foundry like that represented in the plan, fig. 467., will consume about 300 tons of coke in melting 1240 tons of cast iron; consisting of 940 tons of pigs of different qualities, and 300 tons of broken castings, gate-pieces, &c. Thus, it appears that 48 pounds of coke are consumed for melting every 2 cwt. of metal.

Somewhat less coke is consumed when the fusion is pushed more rapidly to collect a great body of melted metal, for casting heavy articles; and more is consumed when, as in making many small castings, the progress of the founding has to be slackened from time to time; otherwise, the metal would remain too long in a state of fusion, and probably become too cold to afford sharp impressions of the moulds.

It sometimes happens that in the same day, with the same furnace, pieces are to be cast containing several proportions of different kinds of iron; in which case, to prevent an intermixture with the preceding or following charges, a considerable bed of coke is interposed. Though there be thus a little waste of fuel, it is compensated by the improved adaptation of the castings to their specific objects. The founding generally begins at about 3 o’clock, P. M., and goes on till 6 or 8 o’clock. One founder, aided by four labourers for charging, &c., can manage two furnaces.

The following is the work of a well-managed foundry in Derby.

200 lbs. of coke are requisite to melt, or bring down (in the language of the founders), 1 ton of cast-iron, after the cupola has been brought to its proper heat, by the combustion in it of 9 baskets of coak, weighing by my trials, 40 pounds each, = 360 lbs.

The chief talent of the founder consists in discovering the most economical mixtures, and so compounding them as to produce the desired properties in the castings. One piece, for example, may be required to have great strength and tenacity to bear heavy weights or strains; another must yield readily to the chisel or the file; a third must resist sudden alternations of temperature; and a fourth must be pretty hard.

The filling in of the melted metal is managed in two ways. For strong pieces, whose moulds can be buried in the ground at 7 or 8 yards distance from the furnace, the metal may be run in gutters, formed in the sand of the floor, sustained by plates or stones. The clay plug is pierced with an iron rod, when all is ready.

When from the smaller size, or greater distance of the moulds, the melted metal cannot be run along the floor from the furnace, it is received in cast-iron pots or ladles, lined with a coat of loam. These are either carried by the hands of two or more men, or transported by the crane. Between the successive castings, the discharge hole of the furnace is closed with a lump of clay, applied by means of a stick, having a small disc of iron fixed at its end.

After the metal is somewhat cooled, the moulds are taken asunder, and the excrescences upon the edges of the castings are broken off with a hammer. They are afterwards more carefully trimmed or chipped by a chisel when quite cold. The loss of weight in founding is about 6-1/2 per cent. upon the pig iron employed. Each casting always requires the melting of considerably more than its own weight of iron. This excess forms the gates, false seams, &c.; the whole of which being deducted, shows that 1 cwt. of coke is consumed for every 3 cwt. of iron put into the furnace; for every 138 cwt. of crude metal, there will be 100 cwt. of castings, 32 of refuse pieces, and 6 of waste.

Explanation of the plates.

Manner of constructing the Mould of a Sugar-pan.

Fig. 468. View of the pan. -- 469. Flat ring of cast-iron for supporting the inner mould. -- 470. Construction of the inner mould. -- 471. Formation of the outer surface of the pan. -- 472. Finished mould. -- 473. Position of the two flat cast-iron rings, destined to sustain the moulds of the inner and the outer surface.

Gas-retort Moulding.

-- 474. Vertical projection, perpendicular to the axis of the retort; and two sections, the one upright, the other horizontal. -- 475. Construction of the core of the retort. -- 476. Disposition of the outer mould. -- 477. Adjustment of the core in the mould. -- 478. Cupola furnace. It is 3 feet wide within, and 13-1/2 high.

m m, solid body of masonry, as a basis to the furnace.

b b, octagonal platform of cast iron, with a ledge in which the plates a a a a are engaged.

a a, eight plates of cast iron, 1 inch thick, absolutely similar; only one of them is notched at its lower part in c, to allow the melted metal to run out, and two of the others have six apertures g g g, &c. to admit the tuyères.

c, orifice for letting the metal flow out. A kind of cast iron gutter, e, lined with loam is fitted to the orifice.

d, hoops of hammered iron, 4-1/4 inches broad; one half of an inch thick for the bottom ones; and a quarter of an inch for the upper ones. The intermediate hoops decrease in thickness from below upwards between these limits.

e, cast iron gutter or spout, lined with loam, for running off the metal.

f f, cylindrical piece of cast iron, for increasing the height and draught of the furnace.

g, side openings for receiving the tuyères, of which there are six upon each side of the furnace. Each of them may be shut at pleasure, by means of a small cast iron plate h, made to slide horizontally in grooves sunk in the main plate, pierced with the holes g g.

k k, interior lining of the surface, made of sand, somewhat argillaceous, in the following way. After having laid at the bottom of the furnace a bed of sand a few inches thick, slightly sloped towards the orifice of discharge, there is set upright, in the axis of the cupola, a wooden cylinder of its whole height, and of a diameter a little less than that of the vacant space belonging to the top of the furnace. Sand is to be then rammed in so as to fill the whole of the furnace; after which the wooden cylinder is withdrawn, and the lining of sand is cut or shaved away, till it has received the proper form.

This lining lasts generally 5 or 6 weeks, when there are 6 meltings weekly.

i i, cast iron circular plate, through which the mouth of the furnace passes, for protecting the lining in k during the introduction of the charges.

N N, level of the floor of the foundry. The portion of it below the running out orifice consists of sand, so that it may be readily sunk when it is wished to receive the melted metal in ladles or pots of large dimensions.

The fan distributes the blast from the main pipe to three principal points, by three branch tubes of distribution. A register, consisting of a cast-iron plate sliding with friction in a frame, serves to intercept the blast at any moment, when it is not desirable to stop the moving power. A large main pipe of zinc or sheet iron is fitted to the orifice of the slide valve. It is square at the beginning, or only rounded at the angles; but at a little distance it becomes cylindrical, and conducts the blast to the divaricating points. There, each of the branches turns up vertically, and terminates at b b, fig. 479., where it presents a circular orifice of 7-1/2 inches. Upon each of the upright pipes b, the one end of an elbow-tube of zinc c c c c, fig. 479., is adjusted rather loosely, and the other end receives a tuyère of wrought iron d d, through the intervention of a shifting hose or collar of leather c c d, hooped with iron wire to both the tube and the tuyère. The portion c c c c may be raised or lowered, by sliding upon the pipe b, in order to bring the nozzle of the tuyère d d, to the requisite point of the furnace. The portion c c c c may be made also of wrought iron. A power of 4 horses is adequate to drive this fan, for supplying blast to 3 furnaces.

The founders have observed the efflux of air was not the same when blown into the atmosphere, as it was when blown into the furnaces; the velocity of the fan, with the same impulsive power, being considerably increased in the latter case. They imagine that this circumstance arises from the blast being sucked in, so to speak, by the draught of the furnace, and that the fan then supplied a greater quantity of air.

The following experimental researches show the fallacy of this opinion. Two water syphons, e e e, f f f, made of glass tubes, one-fifth of an inch in the bore, were inserted into the tuyère, containing water in the portions g g g, h h h. The one of these manometers for measuring the pressure of the air was inserted at k, the other in the centre of the nozzle. The size of this glass tube was too small to obstruct in any sensible degree the outlet of the air. It was found that when the tuyères of the fan discharged into the open air, the expenditure by a nozzle of a constant diameter was proportional to the number of the revolutions of the vanes. It was further found, that when the speed of the vanes was constant, the expenditure by one or by two nozzles was proportional to the total area of these nozzles. The following formulæ give the volume of air furnished by the fan, when the number of turns and the area of the nozzles are known.

25·32 S n Volume = --------- (1) 1,000,000

0·86´6´7 S n Volume = ------------ (2) 1,000,000

The volume is measured at 32° Fahr., under a pressure of 29·6 inches barom.

S = is the total area of the orifices of the tuyères in square inches.

n = the number of turns of the vanes in a minute.

After measuring the speed of the vanes blowing into the atmosphere, if we introduce the nozzle of discharge into the orifice of the furnace, we shall find that their speed immediately augments in a notable degree. We might, therefore, naturally suppose that the fan furnishes more air in the second case than in the first; but a little reflection will show that it is not so. In fact, the air which issues in a cold state from the tuyère encounters instantly in the furnace a very high temperature, which expands it, and contributes, along with the solid matters with which the furnace is filled, to diminish the facility of the discharge, and consequently to retard the efflux by the nozzles. The oxygen gas consumed is replaced by a like volume of carbonic acid gas, equally expansible by heat. Reason leads us to conclude that less air flows from the nozzles into the furnace than into the open atmosphere.

The increase in the velocity of the vanes takes place precisely in the same manner, when after having made the nozzles blow into the atmosphere, we substitute for these nozzles others of a smaller diameter, instead of directing the larger ones into the furnace. Hence we may conceive that the proximity of the charged furnace acts upon the blast like the contraction of the nozzles. When the moving power is uniform, and the velocity of the vanes remains the same, the quantity of air discharged must also be the same in the two cases.

Two tuyères, one 5 inches in diameter, the other 4-1/2, and which, consequently, presented a total area of 35-1/2 square inches, discharged air into one of the furnaces, from a fan whose vanes performed 654 turns in the minute. These two nozzles being briskly withdrawn from the furnace, and turned round to the free air, while a truncated pasteboard cone of 3-1/2 inches diameter was substituted for the nozzle of 4-1/2 inches, whereby the area of efflux was reduced to 29·3 square inches, the velocity of the vanes continued exactly the same. The inverse operation having been performed, that is to say, the two original nozzles having been smartly replaced in the furnace, to discover whether or not the moving power had changed in the interval of the experiment, they betrayed no perceptible alteration of speed. From the measures taken to count the speed, the error could not exceed 3 revolutions per minute, which is altogether unimportant upon the number 654.

It follows, therefore, that when the vanes of the fan have the velocity of 654 turns per minute, the expenditure by two nozzles, whose joint area is 35-1/2 square inches, both blowing into a furnace, is to the expenditure which takes place, when the same nozzles blow into the air, as 35·5 is to 29·3; that is, a little more than 4-fifths.

If this be, as is probable, a general rule for areas and speeds considerably different from the above, to find the quantity of air blown into one or more furnaces by the fan, we should calculate the volume by one of the above formulæ (1) or (2), and take 4-fifths of the result, as the true quantity.

The fan A C here represented is of the best excentric form, as constructed by Messrs. Braithwaite and Ericsson. D is the circular orifice round the axis by which the air is admitted; and C C B is the excentric channel through which the air is wafted towards the main discharge pipe E.

FOUNTAIN; a stream of water rising up through the superficial strata of the earth. See ARTESIAN WELLS.

FOXING, is a term employed by brewers to characterize the souring of beer, in the process of its fermentation or ripening.

FRANKFORT BLACK; is made by calcining vine branches, and the other refuse lees of the vinegar vats in Germany. They must be previously washed.

FREEZING. (Congelation, Fr.; Gefrierung, Germ.) The three general forms, solid, liquid, and gaseous, under one or other of which all kinds of matter exist, seem to be immediately referrible to the influence of heat; modifying, balancing, or subduing the attraction of cohesion. Every solid may be liquefied, and every liquid may be vaporized, by a certain infusion of caloric, whether this be regarded as a moving power, or an elastic essence. The converse of this proposition is equally true; for many gases, till lately styled permanent, may be liquefied, nay, even solidified, by diminution of their temperature, either alone, or aided by a condensing force, to bring their particles within the sphere of aggregative attraction. When a solid is transformed into a liquid, and a liquid into a gas or vapour, a quantity more or less considerable of heat is absorbed, or becomes latent, to use the term of Dr. Black, the celebrated discoverer of this great law of nature. When the opposite transformation takes place, the heat absorbed is again emitted, or what was latent becomes sensible caloric. Upon the first principle, or the absorption of heat, are founded the various artificial methods of producing cold and congelation.

Tables, exhibiting a collective view of all the Frigorific Mixtures contained in Mr. Walker’s publication, 1808.

I.--Table consisting of Frigorific Mixtures, composed of ice, with chemical salts and acids.

Frigorific Mixtures with Ice.

+-------------------------------+-----------------+------------+ | MIXTURES. | Thermometer |Deg. of cold| | | sinks. | produced. | +-------------------------------+-----------------+------------+ |Snow, or pounded ice 2 parts| } to -5° | * | |Muriate of soda 1 | } | | +-------------------------------+ }---------+------------+ |Snow, or pounded ice 5 parts| } | | |Muriate of soda 2 |From } to -12°| * | |Muriate of ammonia 1 | } | | +-------------------------------+any } --------+------------+ |Snow, or pounded ice 24 parts| } | | |Muriate of soda 10 |tempe- } to -18°| * | |Muriate of ammonia 5 | } | | |Nitrate of potash 5 |rature } | | +-------------------------------+ }---------+------------+ |Snow, or pounded ice 12 parts| } | | |Muriate of soda 5 | } to -25°| * | |Nitrate of ammonia 5 | } | | +-------------------------------+-----------------+------------+ |Snow 3 parts|From +32° to -23°| 55 | |Diluted sulphuric acid 2 | | | +-------------------------------+-----------------+------------+ |Snow 8 parts|From +32° to -27°| 59 | |Muriatic acid 5 | | | +-------------------------------+-----------------+------------+ |Snow 7 parts|From +32° to -30°| 62 | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Snow 4 parts|From +32° to -40°| 72 | |Muriate of lime 5 | | | +-------------------------------+-----------------++-----------+ |Snow 2 parts|From +32° to -50°| 82 | |Cryst. muriate of lime 3 | | | +-------------------------------+-----------------+------------+ |Snow 3 parts|From +32° to -51°| 83 | |Potash 4 | | | +-------------------------------+-----------------+------------+

N. B.--The reason for the omissions in the last column of the preceding table is, the thermometer sinking in these mixtures to the degree mentioned in the preceding column, and never lower, whatever may be the temperature of the materials at mixing.

II.--Table, consisting of Frigorific Mixtures, having the power of generating or creating cold, without the aid of ice, sufficient for all useful and philosophical purposes, in any part of the world at any season.

Frigorific Mixtures without Ice.

+-------------------------------+-----------------+------------+ | MIXTURES. | Thermometer |Deg. of cold| | | sinks. | produced. | +-------------------------------+-----------------+------------+ |Muriate of ammonia 5 parts| | | |Nitrate of potash 5 |From +50° to +10°| 40° | |Water 16 | | | +-------------------------------+-----------------+------------+ |Muriate of ammonia 5 parts| | | |Nitrate of potash 5 |From +50° to +4° | 46 | |Sulphate of soda 8 | | | |Water 16 | | | +-------------------------------+-----------------+------------+ |Nitrate of ammonia 1 part |From +50° to +4° | 46 | |Water 1 | | | +-------------------------------+-----------------+------------+ |Nitrate of ammonia 1 part | | | |Carbonate of soda 1 |From +50° to -7° | 57 | |Water 1 | | | +-------------------------------+-----------------+------------+ |Sulphate of soda 3 parts|From +50° to -3° | 53 | |Diluted nitric acid 2 | | | +-------------------------------+-----------------+------------+ |Sulphate of soda 6 parts| | | |Muriate of ammonia 4 |From +50° to -10°| 60 | |Nitrate of potash 2 | | | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Sulphate of soda 6 parts| | | |Nitrate of ammonia 5 |From +50° to -14°| 64 | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Phosphate of soda 9 parts|From +50° to -12°| 62 | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Phosphate of soda 9 parts| | | |Nitrate of ammonia 6 |From +50° to -21°| 71 | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Sulphate of soda 8 parts|From +50° to 0° | 50 | |Muriatic acid 5 | | | +-------------------------------+-----------------+------------+ |Sulphate of soda 5 parts|From +50° to +3° | 47 | |Diluted sulphuric acid 4 | | | +-------------------------------+-----------------+------------+

N. B.--If the materials are mixed at a warmer temperature than that expressed in the table, the effect will be proportionably greater; thus, if the most powerful of these mixtures be made when the air is +85°, it will sink the thermometer to +2°.

III.--Table consisting of Frigorific Mixtures selected from the foregoing Tables, and combined so as to increase or extend cold to the extremest degrees.

Combinations of Frigorific Mixtures.

+-------------------------------+-----------------+------------+ | MIXTURES. | Thermometer |Deg. of cold| | | sinks. | produced. | +-------------------------------+-----------------+------------+ |Phosphate of soda 5 parts| | | |Nitrate of ammonia 3 |From 0° to -34° | 34 | |Diluted nitric acid 4 | | | +-------------------------------+-----------------+------------+ |Phosphate of soda 3 parts| | | |Nitrate of ammonia 2 |From -34° to -50°| 16 | |Diluted mixed acids 4 | | | +-------------------------------+-----------------+------------+ |Snow 3 parts|From 0° to -46° | 46 | |Diluted nitric acid 2 | | | +-------------------------------+-----------------+------------+ |Snow 8 parts| | | |Diluted sulphuric acid 3 |From -10° to -56°| 46 | |Diluted nitric acid 3 | | | +-------------------------------+-----------------+------------+ |Snow 1 part |From -20° to -60°| 40 | |Diluted sulphuric acid 1 | | | +-------------------------------+-----------------+------------+ |Snow 3 parts|From +20° to -48°| 68 | |Muriate of lime 4 | | | +-------------------------------+-----------------+------------+ |Snow 3 parts|From +10° to -54°| 64 | |Muriate of lime 4 | | | +-------------------------------+-----------------+------------+ |Snow 2 parts|From -15° to -68°| 53 | |Muriate of lime 3 | | | +-------------------------------+-----------------+------------+ |Snow 1 part |From 0° to -66° | 66 | |Cryst. muriate of lime 2 | | | +-------------------------------+-----------------+------------+ |Snow 1 part |From -40° to -73°| 33 | |Cryst. muriate of lime 3 | | | +-------------------------------+-----------------+------------+ |Snow 8 parts|From -68° to -91°| 23 | |Diluted sulphuric acid 10 | | | +-------------------------------+-----------------+------------+

N. B.--The materials in the first column are to be cooled, previously to mixing, to the temperature required, by mixtures taken from either of the preceding tables.

Water absorbs 1000 degrees of heat in becoming vapour; whence, if placed in a saucer within an exhausted receiver, over a basin containing strong sulphuric acid, it will freeze by the rapid absorption of its heat into the vapour so copiously formed under these circumstances.

But the most powerful means of artificial refrigeration is afforded by the evaporation of liquefied carbonic acid gas; for the frozen carbonic acid thus obtained, has probably a temperature 100° under zero; so that when a piece of it is laid upon quicksilver, it instantly congeals this metal. The more copious discussion of this subject belongs to chemical science.

FRENCH BERRIES; Berries of Avignon.

FRICTION, counteraction of; see LUBRICATION.

FRIT; see ENAMEL and GLASS.

FUEL; (Combustible, Fr; Brennstoff, Germ.).

Such combustibles as are used for fires or furnaces are called fuel, as wood, turf, pitcoal. These differ in their nature, and in their power of giving heat.

I. Wood, which is divided into hard and soft. To the former belong the oak, the beech, the alder, the birch, and the elm; to the latter, the fir, the pine of different sorts, the larch, the linden, the willow, and the poplar.

Under like dryness and weight, different woods are found to afford equal degrees of heat in combustion. Moisture diminishes the heating power in three ways; by diminishing the relative weight of the ligneous matter, by wasting heat in its evaporation, and by causing slow and imperfect combustion. If a piece of wood contain, for example, 25 per cent. of water, then it contains only 75 per cent. of fuel, and the evaporation of that water will require 1/28 part of the weight of the wood. Hence the damp wood is of less value in combustion by 8/28 or 2/7 than the dry. The quantity of moisture in newly felled wood amounts to from 20 to 50 per cent.; birch contains 30, oak 35, beech and pine 39, alder 41, fir 45. According to their different natures, woods which have been felled and cleft for 12 months contain still from 20 to 25 per cent. of water. There is never less than 10 per cent. present, even when it has been kept long in a dry place, and though it be dried in a strong heat, it will afterwards absorb 10 or 12 per cent. of water. If it be too strongly kiln dried, its heating powers are impaired by the commencement of carbonization, as if some of its hydrogen were destroyed. It may be assumed as a mean of many experimental results, that 1 pound of artificially dried wood will heat 35 pounds of water from the freezing to the boiling point; and that a pound of such wood as contains from 20 to 25 per cent. of water will heat 26 pounds of ice-cold water to the same degree. It is better to buy wood by measure than by weight, as the bulk is very little increased by moisture. The value of different woods for fuel is inversely as their moisture, and this may easily be ascertained by taking their shavings, drying them in a heat of 140° F., and seeing how much weight they lose.

From every combustible the heat is diffused either by radiation or by direct communication to bodies in contact with the flame. In a wood fire the quantity of radiating heat is to that diffused by the air, as 1 to 3; or it is one fourth of the whole heating power.

II. Charcoal. The different charcoals afford, under equal weights, equal quantities of heat. We may reckon, upon an average, that a pound of dry charcoal is capable of heating 73 pounds of water from the freezing to the boiling point; but when it has been for some time exposed to the air, it contains at least 10 per cent. of water, which is partially decomposed in the combustion into carburetted hydrogen, which causes flame, whereas pure dry charcoal emits none.

A cubic foot of charcoal from soft wood weighs upon an average from 8 to 9 pounds, and from hard wood 12 to 13 pounds; and hence the latter are best adapted to maintain a high heat in a small compass. The radiating heat from charcoal fires constitutes one third of the whole emitted.

III. Pitcoal. The varieties of this coal are almost indefinite, and give out very various quantities of heat in their combustion. The carbon is the heat-giving constituent, and it amounts, in different coals, to from 75 to 95 per cent. One pound of good pitcoal will, upon an average, heat 60 pounds of water from the freezing to the boiling point. Small coal gives out three-fourths of the heat of the larger lumps. The radiating heat emitted by burning pitcoal is greater than that by charcoal.

IV. The coke of pitcoal.--The heating power of good coke is to that of pitcoal as 75 to 69. One pound of the former will heat 65 pounds of water from 32° to 212°; so that its power is equal to nine-tenths of that of wood charcoal.

V. Turf or peat.--One pound of this fuel will heat from 25 to 30 pounds of water from freezing to boiling. Its value depends upon its compactness and freedom from earthy particles; and its radiating power is to the whole heat it emits in burning, as 1 to 3.

VI. Carburetted hydrogen or coal gas.--One pound of this gas, equal to about 24 cubic feet, disengages in burning, as much heat as will raise 76 pounds of water from the freezing to the boiling temperature.

In the following table the fourth column contains the weight of atmospherical air, whose oxygen is required for the complete combustion of a pound of each particular substance.

+--------------------------+-----------+-----------+-----------+ | Species of combustible. | Pounds of | Pounds of | Weight of | | |water which| boiling |atmospheric| | |a pound can| water |air at 32°,| | | heat from |evaporated | to burn 1 | | |0° to 212°.|by 1 pound.| pound. | +--------------------------+-----------+-----------+-----------+ |Perfectly dry wood | 35·00 | 6·36 | 5·96 | |Wood in its ordinary state| 26·00 | 4·72 | 4·47 | |Wood charcoal | 73·00 | 13·27 | 11·46 | |Pitcoal | 60·00 | 10·90 | 9·26 | |Coke | 65·00 | 11·81 | 11·46 | |Turf | 30·00 | 5·45 | 4·60 | |Turf charcoal | 64·00 | 11·63 | 9·86 | |Carburetted hydrogen gas | 76·00 | 13·81 | 14·58 | |Oil } | | | | |Wax } | 78·00 | 14·18 | 15·00 | |Tallow } | | | | |Alcohol of the shops | 52·60 | 9·56 | 11·60 | +--------------------------+-----------+-----------+-----------+

The quantity of air stated in the fourth column, is the smallest possible required to burn the combustible, and is greatly less than would be necessary in practice, where much of the air never comes into contact with the burning body, and where it consequently never has its whole oxygen consumed. The heating power stated in the second column is also the maximum effect, and can seldom be realized with ordinary boilers. The draught of air usually carries off at least 1/7 of the heat, and more if its temperature be very high when it leaves the vessel. In this case it may amount to one half of the whole heat or more; without reckoning the loss by radiation and conduction, which however may be rendered very small by enclosing the fire and flues within proper non-conducting and non-radiating materials.

It appears that in practice, the quantity of heat which may be obtained from any combustible in a properly mounted apparatus, must vary with the nature of the object to be heated. In heating chambers by stoves, and water boilers by furnaces, the effluent heat in the chimney which constitutes the principal waste, may be reduced to a very moderate quantity, in comparison of that which escapes from the best constructed reverberatory hearth. In heating the boilers of steam engines, one pound of coal is reckoned adequate to convert 7-1/2 pounds of boiling water into vapour; or to heat 41-1/4 pounds of water from the freezing to the boiling point. One pound of fir of the usual dryness will evaporate 4 pounds of water, or heat 22 pounds to the boiling temperature; which is about two-thirds of the maximum effect of this combustible. According to Watt’s experiments upon the great scale, one pound of coal can boil off with the best built boiler, 9 pounds of water; the deficiency from the maximum effect being here 10/57, or nearly one-sixth.

In many cases the hot air which passes into the flues or chimneys may be beneficially applied to the heating, drying, or roasting of objects; but care ought to be taken that the draught of the fire be not thereby impaired, and an imperfect combustion of the fuel produced. For at a low smothering temperature both carbonic oxide and carburetted hydrogen may be generated from coal, without the production of much heat in the fire-place.

To determine exactly the quantity of heat disengaged by any combustible in the act of burning, three different systems of apparatus have been employed; 1. the calorimeter of Lavoisier and Laplace, in which the substance is burned in the centre of a vessel, whose walls are lined with ice; and the amount of ice melted, measures the heat evolved; 2. the calorimeter of Watt and Rumford, in which the degree of heat communicated to a given body of water affords the measure of temperature; and 3. by the quantity of water evaporated by different kinds of fuel in similar circumstances.

If our object be to ascertain the relative heating powers of different kinds of fuel, we need not care so much about the total waste of heat in the experiments, provided it be the same in all; and therefore they should be burned in the same furnace, and in the same way. But the more economically the heat is applied, the greater certainty will there be in the results. The apparatus, fig. 480., is simple and well adapted to make such comparative trials of fuel. The little furnace is covered at top, and transmits its burned air by c, through a spiral tube immersed in a cistern of water, having a thermometer inserted near its top, and another near its bottom, into little side orifices a a, while the effluent air escapes from the upright end of the tube b. Here also a thermometer bulb may be placed. The average indication of the two thermometers gives the mean temperature of the water. As the water evaporates from the cistern, it is supplied from a vessel placed alongside of it. The experiment should be begun when the furnace has acquired an equability of temperature. A throttle valve at c serves to regulate the draught, and to equalize it in the different experiments by means of the temperature of the effluent air. When the water has been heated the given number of degrees, which should be the same in the different experiments, the fire may be extinguished, the remaining fuel weighed, and compared with the original quantity. Care should be taken to make the combustion as vivid and free from smoke as possible.

FULGURATION; designates the sudden brightening of the melted gold and silver in the cupel of the assayer, when the last film of vitreous lead and copper leaves their surface.

FULLER’S EARTH, (Terre à foulon, Argile Smectique, Fr.; Walkererde, Germ.) is a soft, friable, coarse or fine grained mass of lithomarge clay. Its colour is greenish, or yellowish gray; it is dull, but assumes a fatty lustre upon pressure with the fingers, feels unctuous, does not adhere to the tongue, and has a specific gravity varying from 1·82 to 2·19. It falls down readily in water, into a fine powder, with extrication of air bubbles, and forms a non-plastic paste. It melts at a high heat into a brown slag. Its constituents are 53·0 silica; 10·0 alumina; 9·75 red oxide of iron; 1·25 magnesia; 0·5 lime; 24 water, with a trace of potash. Its cleansing action upon woollen stuffs depends upon its power of absorbing greasy matters. It should be neither tenacious nor sandy; for in the first case, it would not diffuse itself well through water, and in the second it would abrade the cloth too much. The finely divided silica is one of its useful ingredients.

Fuller’s earth is found in several counties of England; but in greatest abundance in Bedfordshire, Berkshire, Hampshire, and Surry.

In the county of Surry there are great quantities of fuller’s earth found about Nutfield, Ryegate, and Blechingley, to the south of the Downs, and some, but of inferior quality, near Sutton and Croydon, to the north of them. The most considerable pits are near Nutfield, between which place and Ryegate, particularly on Redhill, about a mile to the east of Ryegate, it lies so near the surface as frequently to be turned up by the wheels of the waggons. The fuller’s earth to the north of the road between Redhill and Nutfield, and about a quarter of a mile from the latter place, is very thin; the seam in general is thickest on the swell of the hill to the south of the road. It is not known how long this earth has been dug in Surry; the oldest pit now wrought is said to have lasted between 50 and 60 years, but it is fast wearing out. The seam of fuller’s earth dips in different directions. In one, if not in more cases, it inclines to the west with a considerable angle. There are two kinds of it, the blue and the yellow: the former, on the eastern side of the pit, is frequently within a yard of the surface, being covered merely with the soil--a tough, wet, clayey loam. A few yards to the west, the blue kind appears with an irony sand-stone, of nearly two yards in thickness, between it and the soil. The blue earth in this pit is nearly 16 feet deep. In some places the yellow kind is found lying upon the blue; there seems, indeed, to be no regularity either in the position or inclination of the strata where the fuller’s earth is found, nor any mark by which its presence could be detected. It seems rather thrown in patches than laid in any continued or regular vein. In the midst of the fuller’s earth are often found large pieces of stone of a yellow colour, translucent and remarkably heavy, which have been found to be sulphate of barytes, encrusted with quartzose crystals. These are carefully removed from the fuller’s earth, as the workmen say they often spoil many tons of it which lie about them. There is also found with the yellow fuller’s earth a dark brown crust, which the workmen consider as injurious also. In Surry the price of fuller’s earth seems to have varied very little, at least for these last 80 years. In 1730, the price at the pit was 6_d._ a sack, and 6_s._ per load or ton. In 1744, it was nearly the same. It is carried in waggons, each drawing from three to four tons, to the beginning of the iron railway near Westham, along which it is taken to the banks of the Thames, where it is sold at the different wharfs for about 25_s._ or 26_s._ per ton. It is then shipped off either to the north or west of England.

The next characteristic stratum, owing to its forming a ridge of conspicuous hills through the country, is the Woburn land, a thick ferruginous stratum, which below its middle contains a stratum of fuller’s earth. This is thicker and more pure in Aspley and Hogstye-end, two miles north-west of Woburn, than in any known place.

Fuller’s earth is found at Tillington, and consumed in the neighbouring fulling mills.

Mode of preparing fuller’s earth:--

After baking it is thrown into cold water, where it falls into powder, and the separation of the coarse from the fine is effectually accomplished, by a simple method used in the dry colour manufactories, called washing over. It is done in the following manner: Three or four tubs are connected on a line by spouts from their tops; in the first the earth is beat and stirred, and the water, which is continually running from the first to the last through intermediate ones, carries with it and deposits the fine, whilst the coarse settles in the first. The advantages to be derived from this operation are, that the two kinds will be much fitter for their respective purposes of cleansing coarse or fine cloth; for without baking the earth they would be unfit, as before noticed, to incorporate so minutely with the water in its native state; it would neither so readily fall down, nor so easily be divided into different qualities, without the process of washing over. When fuel is scarce for baking the earth, it is broken into pieces of the same size, as mentioned above, and then exposed to the heat of the sun.

The various uses of fuller’s earth may be shortly explained. According to the above method, the coarse and fine of one pit being separated, the first is used for cloths or an inferior, and the second for those of a superior quality. The yellow and the blue earths of Surry are of different qualities naturally, and are like the above, obtained artificially, and used for different purposes. The former, which is deemed the best, is employed in fulling the kerseymeres and finer cloths of Wiltshire and Gloucestershire, whilst the blue is principally sent into Yorkshire for the coarser cloths. Its effects on these cloths is owing to the affinity which alumine has for greasy substances; it unites readily with them, and forms combinations which easily attach themselves to different stuffs, and thereby serve the purpose of mordants in some measure. The fullers generally apply it before they use the soap.

FULLING; for the theory of the process, see FELTING, and WOOL.

FULLING MILL. Willan and Ogle obtained a patent in 1825 for improved fulling machinery, designed to act in a similar way to the ordinary stocks, in which cloths are beaten, for the purpose of washing and thickening them; but the standard and the bed of the stocks are made of iron instead of wood as heretofore; and a steam vessel is placed under the bed, for heating the cloths during the operation of fulling; whereby their appearance is said to be greatly improved.

Fig. 480*. is a section of the fulling machine or stocks; a, is a cast-iron pillar, made hollow for the sake of lightness; b, is the bed of the stocks, made also of iron, and polished smooth, the side of the stock being removed to shew the interior; c, is the lever that carries the beater d. The cloths are to be placed on the bed b, at bottom, and water allowed to pass through the stock, when by the repeated blows of the beater d, which is raised and let fall in the usual way, the cloths are beaten, and become cleansed and fulled.

A part of the bed at e, is made hollow, for the purpose of forming a steam box, into which steam from a boiler is introduced by a pipe with a stop-cock. This steam heats the bed of the stock, and greatly facilitates, as well as improves the process of cleansing and fulling the cloths.

The smoothness of the surface of the polished metal, of which the bed of the stock is constituted, is said to be very much preferable to the roughness of the surface of wood of which ordinary fulling stocks are made, as by these iron stocks less of the nap or felt of the cloth is removed, and its appearance when finished is very much superior to cloths fulled in ordinary stocks.

In the operation of fulling, the cloths are turned over on the bed, by the falling of the beaters, but this turning over of the cloths will depend in a great measure upon the form of the front or breast of the stock. In these improved stocks therefore, there is a contrivance by which the form of the front may be varied at pleasure, in order to suit cloths of different qualities; f, is a movable curved plate, constituting the front of the stock; its lower part is a cylindrical rod, extending along the entire width of the bed, and being fitted into a recess, forms a hinge joint upon which the curved plate moves; g, is a rod attached to the back of the curved plate f, with a screw thread upon it; this rod passes through a nut h, and by turning this nut, the rod is moved backward or forward, and consequently, the position of the curved plate altered.

The nut h, is a wheel with teeth, taking into two other similar toothed wheels, one on each side of it, which are likewise the nuts of similar rods jointed to the back of the curved plate f; by turning the central wheel, therefore, which may be done by a winch, the other two wheels are turned also, and the curved plate moved backward or forward. At the upper part of the plate there are pins passing through curved slots, which act as guides when the plate is moved.

The patentees state in conclusion, that steam has been employed before for heating cloths while fulling them, they therefore do not exclusively claim its use, except in the particular way described; the advantages arising from the construction of iron stocks, with polished surfaces in place of wooden ones, together with the movable curved plates described, are in their opinion “sufficiently important to constitute a patent right.”

FULMINATES, or fulminating powders. Of these explosive compounds, there are several species; such as fulminating gold, mercury, platinum, silver; besides the old fusible mixture of nitre, sulphur, and potash. The only kind at all interesting in a manufacturing point of view is the fulminate of mercury, now so extensively used as a priming to the caps of percussion locks. Having published a paper in the Journal of the Royal Institution for 1831, upon gunpowder (see GUNPOWDER), the result of an elaborate suite of experiments, I was soon afterwards requested by the Hon. the Board of Ordnance to make such researches as would enable me to answer, in a satisfactory practical manner, a series of questions upon fulminating powders, subservient to the future introduction of percussion musquets into the British army. The following is a verbatim copy of my report upon the subject:--

To the Secretary of the Board of Ordnance.

“SIR,--I have the honour of informing you, for the instruction of the Honourable the Master General and the Board of Ordnance, that the researches on fulminating mercury, which I undertook by their desire, have been brought to a satisfactory conclusion, after a numerous, diversified, and somewhat hazardous series of experiments. The following are the questions submitted to me, with their respective answers:--

Question 1. What proportions of mercury, with nitric acid and alcohol of certain strengths, will yield the greatest quantity of pure fulminate of mercury?

Answer. One hundred parts, by weight, of mercury, must be dissolved with a gentle heat, in 1000 parts (also by weight) of nitric acid, spec. gr. 1·4; and this solution, at the temperature of about 130° Fahr. must be poured into 830 parts by weight of alcohol, spec. gr. 0·830.--Note. 830 parts of such alcohol, by weight, constitute 1000 by measure; and 1000 parts of such nitric acid, by weight, constitute 740 by measure. Hence, in round numbers, one ounce weight of quicksilver must be dissolved in 7-1/2 oz. measures of the above designated nitric acid, and the resulting solution must be poured into 10 oz. measures of the said alcohol.

Question 2. What is the most economical and safe process for conducting the manipulation, either as regards the loss of nitrous gas and residuum, or as respects danger to the operator; also, what is the readiest and safest mode of mixing the fulminate intimately with its due proportions of common gunpowder.

Answer. The mercury should be dissolved in the acid in a glass retort, the beak of which is loosely inserted into a large balloon or bottle of glass or earthenware, whereby the offensive fumes of the nitrous gas disengaged during the solution, are, in a considerable measure, condensed into liquid acid, which should be returned into the retort. As soon as the mercury is all dissolved, and the solution has acquired the prescribed temperature of about 130°, it should be slowly poured, through a glass or porcelain funnel, into the alcohol contained in a glass matrass or bottle capable of holding fully 6 times the bulk of the mixed liquids. In a few minutes bubbles of gas will proceed from the bottom of the liquid; these will gradually increase in number and magnitude till a general fermentative commotion, of a very active kind, is generated, and the mixture assumes a somewhat frothy appearance. A white voluminous gas now issues from the orifice of the matrass, which is very combustible, and must be suffered to escape freely into the air, at a distance from any flame. These fumes consist of an ethereous gas, holding mercury in suspension or combination. I have made many experiments with the view of condensing this gas, or, at least, the mercury, but with manifest disadvantage to the perfection of the process of producing fulminate. When the said gas is transmitted, through a glass tube, into a watery solution of carbonate of soda, a little oxide of mercury is, no doubt, recovered; but the pressure on the fermentative mixture, though slight, necessary to the displacement of the soda solution, seems to obstruct or impair the generation of the fulminate; this effect is chiefly injurious towards the end of the operation when the gaseous fumes are strongly impregnated with nitrous gas. When this is not allowed freely to come off, a portion of subnitrate or nitrate of mercury is apt to be formed, to the injury of the general process and the product.

As soon as the effervescence and concomitant emission of gas are observed to cease, the contents of the matrass should be turned out upon a paper double filter, fitted into a glass or porcelain funnel, and washed by the affusion of cold water till the drainings no longer redden litmus paper. The powder adhering to the matrass should be washed out and thrown on the filter by the help of a little water. Whenever the filter is thoroughly drained, it is to be lifted out of the funnel, and opened out on plated copper or stone ware, heated to 212° Fahr. by steam or hot water. The fulminate being thus dried, is to be put up in paper parcels of about 100 grains each; the whole of which may be afterwards packed away in a tight box, or a bottle with a cork stopper. The excellence of the fulminate may be ascertained, by the following characters. It consists of brownish-gray small crystals which sparkle in the sun, are transparent when applied to a slip of glass with a drop of water, and viewed by transmitted light. These minute spangles are entirely soluble in 130 times their weight of boiling water; that is to say, an imperial pint of boiling water will dissolve 67 grs. of pure fulminate. Whatever remains indicates impurity. From that solution beautiful pearly spangles of fulminate fall down as the liquid cools.

It may now be proper to show within what nice and narrow limits the best proportions of the ingredients used in making the fulminate of mercury lie. The following are selected from among many experiments instituted to determine that point, as well as the most economical process.

1. According to the formula given by the celebrated chemist Berzelius, in the 4th vol. of his “Traité de Chimie,” recently published (p. 383.), the mercury should be dissolved in 12 times its weight of nitric acid sp. gr. 1·375; and alcohol of sp. gr. 0·850, amounting to 16·3 times the weight of the mercury, should be poured at intervals into the nitric solution. The mixture is then to be heated till effervescence with the characteristic cloud of gas appears. On the action becoming violent, alcohol is to be poured in from time to time to repress it, till additional 16·3 parts have been employed.

On this process I may remark, that it is expensive, troublesome, dangerous, and unproductive of genuine pure fulminate. One fifth more nitric acid is expended very nearly than what is necessary, and almost four times the weight of alcohol which is beneficial. Of alcohol at 0·83, 8·3 parts by weight are sufficient; whereas Berzelius prescribes nearly 4 times this quantity in weight, though the alcohol is somewhat weaker, being of sp. gr. 0·850. By using such an excess of alcohol, much of the fulminate is apt to be revived into globules of quicksilver at the end of the process, as I showed in my paper on this subject published in the Journal of the Royal Institution two years ago. There is no little hazard in pouring the alcohol into the nitric solution; for at each effusion an explosive blast takes place, whereas by pouring the solution into the alcohol, as originally enjoined by the Hon. Mr. Howard, the inventor of the process, no danger whatever is incurred. 100 parts of mercury treated in the way recommended by Berzelius afforded me only 112 parts of fulminate, instead of the 130 obtained by my much more economical and safe proportions and process from the same weight of quicksilver.

2. If 10 parts of nitric acid of sp. gr. 1·375 be used for dissolving 1 of quicksilver, and if 14 parts of alcohol of sp. gr. 0·85 be thereafter mixed with the solution, the product of such proportions will either be not granular, and therefore not fulminating, or it will be partially granular and partially pulverulent, being a mixture of fulminate and subnitrate of mercury ill adapted for priming detonating caps. Instead of 130 parts of genuine fulminate, as I do obtain, probably not more than 10 parts of powder will be produced, and that of indifferent quality. In fact, whenever the ethereous fermentation is defective, or not vigorous, little true fulminate is generated; but much of the mercury remains in the acidulated alcoholic liquid.

3. If the alcohol be poured in successive portions, and of proper strength (sp. gr. 0·83) into a proper nitric solution of mercury, the explosive action which accompanies each effusion dissipates much of the alcohol, and probably impairs the acid, so that the subsequent ethereous fermentation is defective, and little good fulminate is formed. From 100 parts of mercury submitted to this treatment, I obtained in one experiment carefully made, only 51 parts of a powder, which was impalpable, had a cream colour, and was not explosive either by heat or percussion.

4. When, with 100 parts of mercury, 800 of nitric acid of sp. gr. 1·375 are employed with 650 of alcohol of sp. gr. 846, no fulminate whatever is generated.

5. When with the proper proportions of mercury, acid, and alcohol, the process is advanced into a proper energy of fermentative commotion, if the matrass be immersed in cold water so as materially to repress that action, the process will be impaired, and will turn out ultimately defective both as to the quantity and quality of the fulminate. It is therefore evident that a certain energy or vivacity of etherization is essential to the full success of this curious process, and that any thing which checks it, or obstructs its taking place, is injurious and to be avoided.

When my proportions are observed in making fulminating mercury, somewhat less than one fourth of the nitric acid used in making the solution remains in the alcoholic mixture along with the fulminate. When other proportions are taken, much more acid remains. This acid is not recoverable to any useful or economical purpose, nor is the alcohol that is associated with it. Many distillations with various reagents have led me to this practical conclusion. In fact, when the process is most complete, as described in the first paragraph, the alcohol is entirely and profitably employed in etherization, and generating fulminic acid.

I have made a series of analytical experiments on the pure fulminate of mercury, with the view of determining its composition, the quantity of quicksilver present in it, and consequently the loss of mercury in the operation. I have stated that my maximum product of fulminate from 100 grs. of quicksilver is 130 grs. Occasionally from slight differences in the temperature of the mixture, or the ambient atmosphere, 2 grs. less may be obtained.

A. I dissolved 130 grs. with a gentle heat in muriatic acid contained in a small matrass, adding a few drops of the nitric to quicken the solution. On evaporating it to dryness, with much care to avoid volatilization of the salt, I obtained 125 grs. of corrosive sublimate or bi-chloride of mercury. But 125 grs. of this bi-chloride contain only 91·1 grs. of quicksilver. Therefore, by this experiment, 130 grs. of fulminate contain no more than 91·1 of mercury, indicating an exhalation of 8·9 parts in the form of fumes, or a retention in the residuary liquid of some of these 8·9 parts, out of the 100 originally employed.

B. In another experiment for analysis, 130 grs. dissolved as above, were thrown down by carbonate of soda. 95 grs. of black oxide of mercury were obtained, which are equivalent to 91·2 grs. of quicksilver; affording a confirmation of the preceding result.

C. 130 grs. of fulminate were dissolved in strong muriatic acid, and the solution was decomposed by crystals of proto-muriate of tin at a boiling temperature. The mercury was precipitated in globules to such amount as to verify the two preceding experiments.

Regarding fulminate of mercury as a bi-cyanate, that is, as a compound of one atom or one equivalent prime of deutoxide of mercury, and two primes of cyanic acid, we shall find its theoretical composition to be as follows, hydrogen being the radix, or 1.

2 Primes of Cyanic or fulminic Acid = 34 × 2 = 68 24 1 Deutoxide of Mercury = 216 76 --- --- 284 100

As these 284 parts of fulminate contain 200 of quicksilver, so 142 parts of fulminate will contain 100 of quicksilver. Whence it appears, that when only 130 parts of fulminate can be obtained in practice from 100 of quicksilver, 8-1/2 parts of quicksilver out of the 100 are unproductive, that is, are expended in the etherized gas, or left in the residuary acidulous liquid. By the above experimental and theoretical analysis, 91·5 parts of quicksilver enter into the composition of 130 parts of true crystalline fulminate. The complete accordance here exhibited between theory and practice removes every shadow of doubt as to the accuracy of the statements. 100 parts of fulminate consist of--

Mercury } 70·4 } Peroxide 76·0 Oxygen } 5·6 } Fulminic acid 24 ----- 100·0

Question 3. May the gas or vapour produced by the inflammation of the fulminate of mercury, when combined with a portion of gunpowder, be considered in its nature corrosive of iron or brass?

Answer. I have suggested to Mr. Lovell, of Waltham Abbey works, that the fulminate may be probably diluted most advantageously with spirit varnish made of a proper consistence by dissolving sandarach in alcohol. When well mixed with this varnish, a small drop of the mixture will suffice for priming each copper cap or disc; and as the spirit evaporates immediately, the fulminate will be fixed to the copper beyond the risk of shaking or washing away. On the Continent, tincture of benjamin is used for the same purpose; but as that balsamic resin leaves in combustion a voluminous coal, which sandarach does not, the latter, which is the main constituent of spirit varnish, seems better adapted for this purpose. It is sufficiently combustible, and may be yet made by a due proportion, to soften the violence of the explosive mercury on the nipple of the touch-hole. Fulminate prepared by my formula has no corrosive influence whatsoever on iron or steel; and, therefore, if such a medium of applying it, as I have now taken leave to suggest, should be found to answer, all fears on the score of corrosion may for ever be set at rest.

Question 4. How far is the mixture (of fulminate and gunpowder) liable to be affected by the moisture of the atmosphere, or by the intrusion of water; and will such an accident affect its inflammability when dried again?

Answer. Well made fulminate, mixed with gunpowder and moistened, undergoes no change, nor is it apt to get deteriorated by keeping any length of time in a damp climate or a hazy atmosphere. Immersion in water would be apt to wash the nitre out of the pulverine; but this result would be prevented if the match or priming mixture were liquefied or brought to the pasty consistence not with water, but spirit varnish. Such detonating caps would be indestructible, and might be alternately moistened and dried without injury.

Question 5. Is it at all probable that the composition would be rendered more inflammable or dangerous of use, by the heat of tropical climates?

Answer. No elevation of temperature of an atmospheric kind, compatible with human existence, could cause spontaneous combustion of the fulminating mercury, or the detonating matches made with it. In fact, its explosive temperature is so high as 367° of Fahrenheit’s scale, and no inferior heat will cause its detonation.

Question 6. Is the mercurial vapour or gas arising from the ignition of a great number of primers, and combined with the smoke of gunpowder in a confined space (as in the case of troops in close bodies, squares, casemates, &c.) likely in its nature to be found prejudicial to human health?

Answer. I have exploded in rapid succession of portions, 100 grains of fulminate of mercury (equivalent to 300 or 400 primers), in a close chamber of small dimensions, without experiencing the slightest inconvenience at the period, or afterwards, though my head was surrounded by the vapours all the time of the operation. These vapours are, in fact, so heavy that they subside almost immediately. When the fulminate mixed with pulverine is exploded in the primers by condensed masses of troops, the mercury will cause no injury to their health, nor one 100th part of the deleterious impression on weak lungs which the gases of exploded gunpowder might by possibility inflict. These gases are all, theoretically speaking, noxious to respiration; such as carbonic acid gas, azote, carburetted hydrogen, and sulphuretted hydrogen, a deadly gas. Yet the soldier who should betray any fear of gunpowder smoke would be an object of just ridicule.”

In the following September, I executed for the Board of Ordnance a set of experiments complementary to those of the memoir, with the view of ascertaining the best manner of protecting the fulminate when applied to the copper caps, from being detached by carriage, or altered by keeping. The following were my results and conclusions.

1. Fulminate of mercury moistened upon copper is speedily decomposed by the superior affinity of the copper over mercury, for oxygen and fulminic acid. Dryness is, therefore, essential to the preservation of the fulminate; and hence charcoal, which is apt to become moist, should not be introduced into percussion caps destined for distant service.

2. An alcoholic solution of sandarach, commonly called spirit varnish, acts powerfully on copper, with the production of a green efflorescence, which decomposes fulminate of mercury. Indeed, sandarach can decompose the salts of copper. It is therefore ill adapted for attaching the fulminate to copper caps.

3. An alcoholic solution of shell-lac acts on copper, though more feebly than the sandarach.

4. A solution of mastic in spirits of turpentine, whether alone or mixed with fulminate, has no action whatever on bright copper, but protects it from being tarnished. Such a varnish is very cheap, dries readily, adheres strongly, screens the fulminate from damp, and does not impair or counteract its detonating powers. This, therefore, is in my opinion the fittest medium for attaching the fulminate, and for softening the force of its impulsion in any degree proportional to the thickness of the varnish.”

Fulminate of mercury is obtained in white grains, or short needles, of a silky lustre, which become gray upon exposure to light, and detonate either by a blow or at a heat under 370° F.; with the disengagement of azote, carbonic acid, as also of aqueous and mercurial vapours; to the sudden formation of which gaseous products the report is due. It detonates even in a moist condition; and when dry it explodes readily when struck between two pieces of iron, less so between iron and bronze, with more difficulty between marble and glass, or between two surfaces of marble or glass. It is hardly possible to explode it by a blow with iron upon lead; and impossible by striking it with iron upon wood. It fulminates easily when rubbed between two wooden surfaces; less so between two of marble, two of iron, or one of iron against one of wood or marble. The larger its crystals, the more apt they are to explode. By damping it with 5 per cent. of water, it becomes less fulminating; the part of it struck still explodes with a proper blow, but will not kindle the adjoining portion. Though moistened with 30 per cent. of water, it will occasionally explode by trituration between a wooden muller and a marble slab, but only to a small extent, and never with any danger to the operator. When an ounce of it, laid upon the bottom of a cask, is kindled, it strikes a round hole down through it, as if it had been exposed to a four-pound shot, without splintering the wood. If a train of fulminate of mercury be spread upon a piece of paper, covered with some loose gunpowder, in exploding the former the latter will not be kindled, but merely scattered. When gunpowder, however, is packed in a cartridge, or otherwise, it may be certainly kindled by a percussion cap of the fulminate, and more completely than by a priming of gunpowder. 8-1/2 parts of gunpowder exploded by a percussion cap, have an equal projectile force as 10 exploded by a flint lock. If we add to this economy in the charge of the barrel, the saving of the powder for priming, the advantage in military service of the percussion system will become conspicuous.

The French calculate that 1 kilogramme of mercury will furnish 1-1/4 kil. (2-1/2 lbs. nearly) of fulminate, which will be sufficient to charge 40,000 percussion caps. For this purpose they grind the crystalline salt along with 30 per cent. of water upon a marble table with a wooden muller; mixing with every 10 parts of the fulminate 6 of gunpowder. A consistent dough is thus obtained, which, being dried in the air, is ready for introducing into the bottoms of the copper caps. One quarter of a grain of the fulminate is said to be fully sufficient for one priming.

Mr. Lovell, of the Royal Manufactory of Arms, has lately executed a series of experiments upon priming powders. His trials, which occupied nearly 18 months, were made for the purpose of ascertaining what is the advantage in point of force obtained by using percussion primes. He had anticipated some extra energy would be imparted to the charge of powder in the barrel, because he had repeatedly proved that a good strong cap, exploded by itself on the nipple of the musquet, (without any charge of gunpowder), will exert sufficient force upon the air within the barrel to blow a candle out at a distance of 12 feet from the muzzle. He concluded also that stopping the escape of fluid from the vent, as is done by the cap, would have some effect, but he attributed most to the quickness and energy with which the powder of the charge is ignited by the vivid stream of flame, generated by the percussion prime. The trials were made from one and the same barrel, having a percussion lock on one side and a flint lock on the other. The balls were fired against Austen’s recoiling target, a very delicate plegometer, beginning with a charge of 150 grains (the present musquet charge), and descending by 10 grains at a time (firing 30 rounds with each weight), down to 50 grains. The machine marked the decrease of force at each reduction in the charge very satisfactorily, and the result of the whole average was that 8·84 parts of gunpowder fired by percussion are equal to 10 parts fired by the flint.

To find out what sort of liberties might be taken with fulminate of mercury in handling it, he placed 3 grains on an anvil, putting the end of a steel punch gently on the top of it, and while so placed he covered the fulminate over with a drachm of dry gunpowder. He then ignited the fulminate by a blow on the punch with the hammer, but not a grain of the gunpowder was lighted, though it was blown about in all directions. He then placed a train of fulminate as thick as a quill, and about 3 feet long, on a table, and covered it over entirely with gunpowder except about an inch at one end; this he lighted with a hot iron, when the whole train went off without blazing a grain of the gunpowder, which he swept together and blew up afterwards with a match. He then took a tin box containing 500 copper caps, made a hole in the top of the box, and through this hole ignited one of the caps in the middle, by means of the punch and hammer on the outside; only two other caps besides the one struck exploded; no injury was sustained by the remainder, except being discoloured. This he tried repeatedly, and always with the same kind of result, never more than 3 or 4 caps exploding. He then made a steel rammer red hot, and passed it through the hole in the box right in amongst the caps, but it only ignited them where the hot iron came in actual contact with the priming composition; when, however, he placed a few grains of gunpowder loose among the caps, the hot iron lighted this, and produced a flame that blew off the whole of them.

The same thing has been tried at Woolwich, where large packages of percussion caps (some thousands) have been fired at with musquet balls, and only a few of the caps actually hit by the ball exploded; but when any cartridges were connected with the packages, the whole, caps and all were blown up. The flame of the fulminate is therefore hazardous, but being so very ethereal, it requires for making primes, an admixture of some combustible matter, as a little gunpowder, to condense or modify the flame.

FULMINIC ACID; (Acide fulminique, Fr.; Knallsäure, Germ.) is the explosive constituent of the fulminating mercury of Howard, and the fulminating silver of Brugnatelli, being generated by the reaction of alcohol and the acid nitrates of these metals. It is a remarkable chemical fact, that fulminic acid has exactly the same composition as cyanic acid; though the salts of the latter possess no detonating property, and afford, in their decomposition by an oxygen acid, ammonia with carbonic acid; while those of the former afford ammonia and prussic acid. All attempts to insulate fulminic acid have proved unsuccessful, as it explodes with the slightest decomposing force. It consists, by weight, of 2 primes of carbon, 1 of azote, and 1 of oxygen; or of two volumes of carbonic acid, and one of azote. When two different bodies, like the above, have the same composition, they are said to be isomeric.

FUMIGATION, is the employment of fumes or vapours to purify articles of apparel, and goods or apartments supposed to be imbued with some infectious or contagious poison or fumes. The vapours of vinegar, the fumes of burning sulphur, explosion of gunpowder, have been long prescribed and practised, but they have in all probability little or no efficacy. The diffusion of such powerful agents as chlorine gas, muriatic acid gas, or nitric acid vapour, should alone be trusted to for the destruction of morbific effluvia.

FUR; see PELTRY.

FURNACE OF ASSAY. Under ASSAY, I have referred to a furnace constructed by Messrs. Anfrye and d’Arcet, which gives some peculiar facilities and economy to the ancient process by fire. It had originally a small pair of bellows attached to it, for raising the heat rapidly to the proper vitrifying pitch. The furnace, 17-1/2 inches high, and 7-1/2 inches wide, made of pottery or fine clay, is represented fig. 481., supported upon a table, having a pair of bellows beneath it. The laboratory is at b, the blow-pipe of the bellows at d, with a stop-cock, and the dome is surmounted by a chimney a, c, in whose lower part there is an opening with a sliding door, for the introduction of the charcoal fuel. The furnace is formed in three pieces; a dome, a body, and an ash-pit. A pair of tongs, a stoking hook, and cupel, are seen to the right hand, and the plan of the stone-ware grate, pierced with conical holes, and a poker, are seen to the left. This grate suits the furnace represented under ASSAY. The following are comparative experiments made by means of this furnace:

+--------+---------+---------+-----------+--------------+-----------+ |Numbers.| Silver | Lead | Time of | Standards. | Charcoal | | |employed.|employed.| Assay. | | used. | +--------+---------+---------+-----------+--------------+-----------+ | 1 |1 Grain. |4 Grains.|12 minutes.|947 millièmes.|173 Grains.| | 2 | -- | -- |11 |950 | 86 | | 3 | -- | -- |13 |949 | 93 | | 4 | -- | -- |10 |949 | 60 | +--------+---------+---------+-----------+--------------+-----------+

Each assay was therefore performed at an average in 11-1/2 minutes, and not much more than a quarter of a pound of charcoal was used. An experiment of verification in the ordinary assay furnace showed the standard to be 949 thousandths.

This furnace becomes a very convenient one for melting small quantities of metals in analyses, by removing the muffle, and closing the several apertures with their appropriate stoppers. A small pedestal may be then set in the middle of the grate, to support a crucible, which may be introduced through the opening h. Coak may also be used as fuel, either by itself or mixed with charcoal. For descriptions of various furnaces, see ASSAY; BEER; COPPER; EVAPORATION; IRON; METALLURGY; ORES; SILVER; TIN; &c.

FUSIBILITY. That property by which solids assume the fluid state.

Some chemists have asserted that fusion is simply a solution in caloric; but this opinion includes too many yet undecided questions, to be hastily adopted.

Fusibility of Metals, as given by M. Thenard.

Centigr. 1. Fusible below a Mercury -39° red heat. Potassium +58° } Gay Lussac and Thenard. Sodium 90 } Tin 210 } Newton. Bismuth 256 } Lead 260 Biot. Tellurium A little less fusible than lead.-- Klaproth. Arsenic Undetermined. Zinc 370° Brongniart. Antimony A little below a red heat. Cadmium Stromeyer.

Pyrometer of Wedgewood.

2. Infusible below Silver 20° Kennedy. a red heat. Copper 27 } Wedgewood. Gold 32 } Cobalt A little less difficult to melt than iron. Iron {130 Wedgewood. {158 Sir G. M’Kenzie. Manganese 160 Guyton. Nickel As manganese.--Richter. Palladium } Molybdenum } Nearly infusible; and to be obtained Uranium } at a forge heat only in small Tungsten } buttons. Chromium } Titanium } Cerium } Osmium } Infusible at the forge furnace. Iridium } Fusible at the oxyhydrogen blowpipe. Rhodium } See BLOWPIPE. Platinum } Columbium }

FUSIBLE METAL. See ALLOY.

FUSTET. (Fustec, Fr.) The wood of the rhus cotinus, a fugitive yellow dye.

FUSTIAN, is a species of coarse thick tweelled cotton, and is generally dyed of an olive, leaden, or other dark colour. Besides the common fustian, which is known by the name of pillow (probably pilaw), the cotton stuffs called corduroy, velverett, velveteen, thicksett, used for men’s wearing apparel, belong to the same fabric. The commonest kind is merely a tweel of four, or sometimes five leaves, of a very close stout texture, and very narrow, seldom exceeding 17 or 18 inches in breadth. It is cut from the loom in half pieces, or ends as they are usually termed, about 35 yards long, and after undergoing the subsequent operations of dyeing, dressing, and folding, is ready for the market.

The draught and cording of common fustian is very simple, being generally a regular or unbroken tweel of four or five leaves. Below are specimens of a few different kinds, selected from those most general in Lancashire.

The number of leaves of heddles are represented by the lines across the paper, and the cording by the cyphers in the little squares, those which raise every leaf being distinguished by these marks, and those which sink them left blank, as more particularly explained in the article TEXTILE FABRIC.

Of velvet, there are properly only two kinds, that with a plain, and that with a tweeled, or, as it is here called, a Genoa ground, or back. When the material is silk, it is called velvet, when cotton, velveteen; and this is the sole difference. In the same way a common tweeled cloth, when composed of silk is called satin; when of cotton, fustian or jean; of woollen, plaiding, serge, or kerseymere; and in the linen trade is distinguished by a variety of names according to the quality or fineness, or the place where the article is manufactured.

No. 1.--Pillow Fustian. No. 2.--Plain Velveret. -+-+-+-+-+------------------------------+-+-+-+-+-+-------------- |0| | | | 4 5 1 § | |0| | | | 3 1 -+-+-+-+-+------------------------------+-+-+-+-+-+-------------- | |0| | | 3 6 2 § |0| | | | | 5 -+-+-+-+-+------------------------------+-+-+-+-+-+-------------- | | |0| | 6 2 3 § |0| | |0|0| 0 2 -+-+-+-+-+------------------------------+-+-+-+-+-+-------------- | | | |0| 5 1 4 § | | | |0| | 6 4 -+-+-+-+-+------------------------------+-+-+-+-+-+-------------- 2 4 3 1 4 6 2 3 1 5

Of the above, each contains four leaves of heddles or healds; that represented by No. 1. is wrought by four treddles, and that which is distinguished by No. 2. by five; the succession of inserting the threads of warp into the heddles will be discovered by the figures between the lines, and the order in which the treddles are to be successively pressed down by the figures below.

No. 3.--Double Jean. No. 4.--Plain Thicksett. -+-+-+-+-+----------------------+-+-+-+-+-+---------------- |0| | |0| 1 § | |0| | | | 8 -+-+-+-+-+----------------------+-+-+-+-+-+---------------- |0| |0| | 2 § | |0|0|0| | 6 4 -+-+-+-+-+----------------------+-+-+-+-+-+---------------- | |0|0| | 3 § | | | |0| | 5 2 -+-+-+-+-+----------------------+-+-+-+-+-+---------------- | |0| |0| 4 § |0| | |0|0| 7 3 1 -+-+-+-+-+----------------------+-+-+-+-+-+---------------- 4 2 3 1 4 6 2 3 1 5 7

These, like the former, are wrought with leaves. No. 3. requires four, and No. 4. five treddles. The succession of inserting the threads of warp, and of working the treddles, are marked by the respective numbers between and under the lines, as in the former example. Both are fabrics of cloth in very general use and estimation as low priced articles.

No. 5.--Best Thicksett. No. 6.--Velvet Tuft. -+-+-+-+-+-+------------------+-+-+-+-+-+--------------------- |0| | |0|0| 3 1 § | |0| | | | 5 3 1 -+-+-+-+-+-+------------------+-+-+-+-+-+--------------------- | | | | |0| 5 § | |0|0| | | 4 2 -+-+-+-+-+-+------------------+-+-+-+-+-+--------------------- | |0| | | | 2 § |0| | |0|0| 4 2 -+-+-+-+-+-+------------------+-+-+-+-+-+--------------------- | |0|0| | | 6 4 § | | | |0| | 5 3 1 -+-+-+-+-+-+------------------+-+-+-+-+-+--------------------- 6 4 2 3 1 6 4 2 3 1 5

These are further specimens of what may be, and is, executed with four leaves, and in both examples five treddles are used. With two other specimens we shall conclude our examples of this description of work, and shall then add a very few specimens of the more extensive kinds.

No. 7.--Cord and Velveret. No. 8.--Thicksett Cord. -+-+-+-+-+-+-----------------------------+-+-+-+-+-+----------------- | |0| | | | 3 1 3 1 §|0| | |0|0| 5 3 1 -+-+-+-+-+-+-----------------------------+-+-+-+-+-+----------------- | |0|0| | | 5 7 5 §| |0| | | | 4 2 -+-+-+-+-+-+-----------------------------+-+-+-+-+-+----------------- |0| | |0|0|6 8 2 §| | | | | | 9 7 -+-+-+-+-+-+-----------------------------+-+-+-+-+-+----------------- | | | |0| | 4 2 6 4 §| |0|0| | | 10 8 6 -+-+-+-+-+-+-----------------------------+-+-+-+-+-+----------------- 4 2 3 1 5 4 3 2 1 6 5

In these the succession of drawing and working are marked like the former. The next are examples of patterns wrought with six leaves. No. 9. has eight, and No. 10. five heddles.

No. 9.--Double Corduroy. No. 10.--Genoa Thicksett. -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- | | | |0| |0 | |0| 1 § | | | |0|0| 1 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- | |0| | | |0 | | | 2 § | | | 0| |0| 2 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- |0|0|0|0|0 | | | | 3 § |0| | 0|0| | 3 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- | | | |0| |0 | | | 4 § | |0| |0|0| 4 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- | |0| | | | | 0| | 5 § |0| | 0| |0| 5 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- | |0| |0| | | | | 6 § | |0| |0| | 6 -+-+-+-+-+--+--+--+-+-----------------+-+-+--+-+-+-------------- 2 4 6 8 10 12 3 1 4 2 5 3 1 7 5 8 6 11 9 7 11 9 1 2 10

In both these the warp is inserted into the heddles the same way. The difference is entirely in the application of the cords, and in the succession of pressing down the treddles. We now give four specimens of the flushed and cut work, known by the name of velveteen. They are also upon six leaves, and the difference is solely in the cording and in the treading.

No. 11. Queen’s Velveteens. No. 12. -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- | | 0| |0|0| | 1 § | | | |0| |0| 1 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- | | | 0| |0| | 2 § | | | 0| |0|0| 2 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- | | | 0|0| | | 3 § | | | |0|0| | 3 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- | | | |0|0| 0| 4 § | | 0| |0| |0| 4 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- | | | 0| |0| | 5 § | | | | |0|0| 5 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- |0| | 0|0| | | 6 § | 0| | |0|0| | 6 -+-+--+--+-+-+--+-----------------+--+--+--+-+-+-+------------- 1 2 12 8 4 2 2 4 3 1 5 7 6 6 8 7 5 9 11 10 10 12 11 9

No. 13.--Plain Velveteen. No. 14.--Genoa Velveteen. -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- | | | | |0| 1 § | | |0| 0| |0| 1 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- |0| | |0| | 2 § | |0|0| | | | 2 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- | | | | |0| 3 § | 0|0| | 0| | | 3 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- | | |0|0| | 4 § | | |0| 0| | | 4 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- | | | | |0| 5 § | |0|0| | 0| | 5 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- | |0| |0| | 6 § | |0| | 0| | | 6 -+-+-+-+-+-+-----------------+--+-+-+--+--+-+------------- 1 3 2 4 8 2 4 8 12 3 1 5 7 6 6 7 5 10 11 9

The additional varieties of figure which might be given are almost endless, but the limits of this article will not admit a further detail. Those already given are the articles in most general use. The varieties of fancy may be indulged to great extent, but it is universally found, that the most simple patterns in every department of ornamental weaving, are those which attract attention and command purchasers. We shall therefore only add two examples of king’s cord or corduroy, two of Genoa and common velvet, and two more of jean. These will be found below.

No. 15.--King’s Cord. No. 16.--Dutch Cord. -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ | | | | |0|0| 1 § | | |0| | | 4 1 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ | | |0| | |0| 2 § | |0| | |0| 5 2 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ | | |0|0| | | 7 3 § |0| | |0| | 6 3 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ | | | |0|0| | 8 4 § | |0|0| | | 7 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ | |0| | |0|0| 5 § |0| |0| |0| 8 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ |0| |0| | | | 6 § |0|0| |0|0| 9 -+-+-+-+-+-+-+---------------------+-+-+-+-+-+------------------ 1 3 8 6 4 2 6 4 2 3 1 5 7 5

No. 17.--Genoa Velvet. No. 18.--Plain Velvet. -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | | |0| | |0| 1 § | | | | | | 1 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | |0|0| 0| | | 2 § | | | | | | 2 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | 0|0| | | | | 3 § | | | | | | 3 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | | |0| 0| | | 4 § | | | | | | 4 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | |0| | 0| | | 5 § | | | | | | 5 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- | |0| | 0| | | 6 § | | | | | | 6 -+--+-+-+--+--+-+-----------------+-+-+-+-+-+------------- 2 4 8 12 3 1 1 3 4 2 8 6 7 5 7 5 10 11 9

After the fustian cloth is taken from the loom-beam, it is carried to the cutter, who rips up the surface-threads of weft, and produces thereby a hairy-looking stuff.

Preparatory to its being cut, the cloth is spread evenly upon a table about six feet long, upon each end of which a roller mounted with a ratchet-wheel is fixed; the one to give off, and the other to wind up the piece, in the above six-feet lengths.

The knife is a steel rod about two feet long, and three-eighths of an inch square, having a square handle at the one end; the other end is tapered away to a blade, as thin as paper. To prevent this point from turning downwards and injuring the cloth, its under side is covered by a guide which serves to stiffen it, as well as to prevent its lower edge from cutting the fustian.

The operative (male or female) grasps the handle in the right hand, and insinuating the projecting point of the guide under the weft, pushes the knife smartly forward through the whole length of six feet, with a certain dexterous movement of the shoulder and right side, balancing the body meanwhile, like a fencer, upon the left foot. This process is repeated upon every adhesive line of the weft.

The next process to which fustians are exposed is steeping in hot water, to take out the dressing paste. They are then dried, reeled, and brushed by a machine, &c. From twenty to thirty pieces, each eighty yards long, may be brushed in an hour. The breadth of the cloth is twenty inches. The maceration is performed by immersing the bundled pieces in tanks of water, heated by waste steam; and the washing by means of a reel or winch, kept revolving rapidly under the action of a stream of cold water, for an hour or longer.

After being thus ripped up, it is taken to the brushing or teazling machine, to make it shaggy.

This consists of a series of wooden rollers, turning freely upon iron axles, and covered with tin-plate, rough with the burs of punched holes; and blocks of wood, whose concave under surfaces are covered with card-cloth or card-brushes, and which are made to traverse backwards and forwards in the direction of the axes of the revolving rollers, during the passage of the cloth over them.

After they are brushed in the machine, the goods are singed by passing their cut surface over a cylinder of iron, laid in a horizontal direction, and kept red hot by a flue. See SINGEING. They are now brushed again by the machine, and once more passed over the singeing surface. The brushing and singeing are repeated a third or even occasionally a fourth time, till the cord acquires a smooth polished appearance.

The goods are next steeped, washed, and bleached, by immersion in solution of chloride of lime. They are then dyed by appropriate chemical means. After which they are padded (imbued by the padding machine of the calico printers) with a solution of glue, and passed over steam cylinders to stiffen them.

Smooth fustians, when cropped or shorn before dyeing, are called moleskins; but when shorn after being dyed, are called beaverteen, they are both tweeled fabrics. Cantoon is a fustian with a fine cord visible upon the one side, and a satiny surface of yarns running at right angles to the cords upon the other side. The satiny side is sometimes smoothed by singeing. The stuff is strong, and has a very fine aspect. Its price is one shilling and sixpence a yard.

Common plain fustian, of a brown or drab colour, with satin top, is sold as low as sevenpence a yard.

A fustian, with a small cord running in an oblique direction, has a very agreeable appearance. It is called diagonal. Moleskin shorn, of a very strong texture, and a drab dyed tint, is sold at 20_d_. per yard.

The weight of 90 yards of the narrow velveteen, in the green or undressed state, is about 24 pounds. The goods made for the German, Italian, and Russian markets are lighter, on account of the peculiarity in the mode of levying the import duty in these countries.

Velveteens as they come from the loom, are sold wholesale by weight, and average a price of 20_d._ per pound. They are usually woven with yarns of Upland and Brazil cotton wool, spun together for the warp; or, sometimes, New Orleans alone. The weft is usually Uplands, sometimes mixed with East India cotton wools.

Trowser velveteens are woven 19 inches wide, if they are to be cut up; if not, they are woven 30 inches, and called beaverteen.

Cutting or cropping fustians by hand is a very laborious and delicate operation. The invention of an improved apparatus for effecting the same end with automatic precision and despatch, was therefore an object of no little interest to this peculiar manufacture of Manchester. An ingenious machine, apparently well calculated for this purpose, was made the subject of a patent by Messrs. William Wells and George Scholefield, of Salford in November, 1834.

FUSTIC. (Bois jaune, Fr.; Gelbholz, Germ.) The old fustic of the English dyer, as the article fustet is their yellow fustic. It is the wood of the Morus tinctoria. It is light, not hard, and pale yellow with orange veins; it contains two colouring matters, one resinous, and another soluble in water. The latter resembles weld, but it has more of an orange cast, and is not so lively.

Its decoctions in water are brightened by the addition of a little glue, and more by curdled milk. This wood is rich in colour, and imparts permanent dyes to woollen stuffs, when aided by proper mordants. It unites well with the blue of the indigo vat, and Saxon blue, in producing green of various shades. Alum, tartar, and solution of tin, render its colour more vivid; sea salt and sulphate of iron deepen its hue. From 5 to 6 parts of old fustic are sufficient to give a lemon colour to 16 parts of cloth. The colour of weld is however purer and less inclining to orange; but that of fustic is less affected by acids than any other yellow dye. This wood is often employed with sulphate of iron in producing olive and brownish tints, which agree well with its dull yellow. For the same reason it is much used for dark greens.

G.

GABRONITE, is a yellowish stony substance, of a greasy lustre and spec. gr. = 2·74; affording no water by calcination; fusible at the blowpipe into an opaque glass; soluble in muriatic acid; solution affords hardly any precipitate by oxalate of ammonia. This mineral is distinguished by the large quantity of soda which it contains; its constituents being,--silica, 54; alumina, 24; soda, 17·25; magnesia, 1·5; oxide of iron, 1·25; water, 2. It belongs to the species Nepheline.

GADOLINITE; called also Yttrite and Ytterbite; is a mineral of a black, brownish, or yellowish colour, granular, or compactly vitreous, and conchoidal fracture; of spec. grav. 4·23? readily scratching glass; fusible at the blowpipe into an opaque glass, sometimes with intumescence. It affords, with acids, a solution that lets fall, with caustic soda, a precipitate partly re-soluble in carbonate of ammonia. It is remarkable for containing from 45 to 55 per cent. of the earth Yttria; its remaining constituents being silica, 25·8; oxide of cerium, 17·92; oxide of iron, 11·43. This mineral is very rare, having been hitherto found only in the neighbourhood of Fahlun and Ytterby, in Sweden; its peculiar constituent was discovered by Professor Gadolin.

GALACTOMETER, or LACTOMETER, is an instrument to ascertain the quality of milk; an article often sophisticated in various ways. Fresh milk, rich in cream, has a less specific gravity, than the same milk after it has been skimmed; and milk diluted with water becomes proportionably lighter. Hence, when our purpose is to determine the quantity of cream, the galactometer may consist merely of a long graduated glass tube standing upright upon a sole. Having filled 100 measures with the recent milk, we shall see, by the measures of cream thrown up, its value in this respect. A delicate long-ranged glass hydrometer, graduated from 1·000 up to 1·060, affords the most convenient means of detecting the degree of watery dilution, provided the absence of thickening materials has been previously ascertained by filtration. Good fresh milk indicates from 1·030 to 1·032; when the cream is removed, 1·035 to 1·037. When its density is less than 1·028, we may infer it has been thinned with water.

GALBANUM, is a gum-resin, which occurs sometimes in yellow, shining tears, easily agglutinated; of a strong durable smell; an acrid and bitter taste; at other times in lumps. It exudes either spontaneously or from incisions made into the stem of the bubon galbanum, a plant of the family of umbelliferæ, which grows in Africa, particularly in Ethiopia. It contains 67 of resin; 19·3 of gum; 6·4 of volatile oil and water; 7·5 of woody fibres and other impurities; with traces of acid malate of lime.

GALENA; (Plomb sulfuré, Fr.; Bleiglanz, Germ.;) is a metallic looking substance of a lead-gray colour, which crystallizes in the cubical system, and is susceptible of cleavages parallel to the faces of the cube; spec. gr. 7·7592; cannot be cut; fusible at the blowpipe with exhalation of sulphureous vapours; is easily reduced to metallic lead. Nitric acid first dissolves it, and then throws down sulphate of lead in a white precipitate; the solution affording with plates of zinc, brilliant laminæ of lead (arbor Saturni.) It consists of sulphur, 13; lead, 85; with a little iron, and sometimes a minute quantity of silver. This is the richest ore of lead, and it occurs in almost every geological formation, in veins, in masses, or in beds. It is almost always accompanied by sulphuret of zinc, different salts of lead, heavy spar, fluor spar, &c. Galena in powder, called Alquifoux, is employed as a glaze for coarse stoneware.

GALIPOT, is a name of a white semi-solid viscid rosin found on fir-trees; or an inferior sort of turpentine, poor in oil.

GALLATES; salts consisting of gallic acid combined with bases; the most important being that with oxide of iron, constituting a principal part of the black dye.

GALLIC ACID, is the peculiar acid extracted from gall-nuts; which see.

GALLIPOLI OIL, is a coarse olive oil, containing more or less mucilage; imported from a sea port so named, of the province of Otranto, in the kingdom of Naples.

GALL-NUTS, or GALLS; (Noix de Galle, Fr.; Galläpfel, Germ.;) are excrescences found upon the loaves and leaf-stalks of a species of oak, called Quercus infectoria, which grows in the Levant. They are produced in consequence of the puncture of the female of the gall wasp, (Cynips folii quercus), made in order to deposit her eggs; round which the juice of the tree exudes, and dries in concentric portions. When the insect gets fully formed, it eats through the nut, and flies off.

The Levant galls are of two different appearances and qualities; the first are heavy, compact, imperforated, the insect having not been sufficiently advanced to eat its way through the shell; prickly on the surface; of a blackish or bluish green hue; about the size of a musket ball. These are called black, blue, or Aleppo galls. The second are light, spongy, pierced with one or more holes; smooth upon the surface, of a pale grayish or reddish yellow colour, generally larger than the first, and are called white galls. Besides the galls of the Levant, others come from Dalmatia, Illyria, Calabria, &c.; but they are of inferior quality, being found upon the Quercus Cerris; they are smaller, of a brownish colour, and of inferior value. The further south the galls are grown, they are reckoned the better.

Galls consist principally of three substances; tannin or tannic acid; yellow extractive; and gallic acid. Their decoction has a very astringent and unpleasant bitter taste. The following are their habitudes with various reagents:--

Litmus paper is powerfully reddened.

Stannous chloride (protomuriate of tin), produces an isabel yellow precipitate.

Alum; a yellowish gray precipitate.

Acetate of lead; a thick yellowish white precipitate.

Acetate of copper; a chocolate brown precipitate.

Ferric sulphate (red sulphate of iron); a blue precipitate.

Sulphuric acid; a dirty yellowish precipitate.

Acetic acid brightens the muddy decoction.

The galls of the Quercus Cerris and common oak (Galles à l’épine, Fr.; Knoppern, Germ.) are of a dark-brown colour, prickly on the surface, and irregular in shape and size. They are used chiefly for tanning in Hungary, Dalmatia, and the southern provinces of the Austrian states, where they abound.

Tannin or tannic acid is prepared as follows: Into a long narrow glass adopter tube shut at its lower orifice with a cotton wick, a quantity of pounded galls are put, and slightly pressed down. The tapering end of the tube being inserted into a matrass or bottle, the vacant upper half of the tube is filled with sulphuric ether, and then closed with a ground-glass stopper. Next day there will be found in the bottle a liquid in two distinct strata; of which the more limpid occupies the upper part, and the other, of a syrupy consistence and amber colour, the lower. More ether must be filtered through the galls, till the thicker liquid ceases to augment. Both are now poured into a funnel, closed with the finger, and after the dense liquor is settled at the bottom, it is steadily run off into a capsule. This, after being washed repeatedly with ether, is to be transferred into a stove chamber, or placed under the receiver of an air pump to be evaporated. The residuary matter swells up in a spongy crystalline form of considerable brilliancy, sometimes colourless, but more frequently of a faintly yellowish hue.

This is pure tannin, which exists in galls to the amount of from 40 to 45 per cent. It is indispensable that the ether employed in the preceding process be previously agitated with water, or that it contain some water, because by using anhydrous ether, not a particle of tannin will be obtained.

Tannic acid is a white or yellowish solid, inodorous, extremely astringent, very soluble in water and alcohol, much less so in sulphuric ether, and uncrystallizable. Its watery solution, out of contact of air, undergoes no change; but if, in a very dilute state, it be left exposed to the atmosphere, it loses gradually its transparency, and lets fall a slightly grayish crystalline matter, consisting almost entirely of gallic acid. For procuring this acid in a perfectly pure state, it is merely necessary to treat that solution thus changed with animal charcoal, and to filter it in a boiling state, through paper previously washed with dilute muriatic acid. The gallic acid will fall down in crystals as the liquid cools.

If the preceding experiment be made in a graduated glass tube containing oxygen over mercury, this gas will be absorbed, and a corresponding volume of carbonic acid gas will be disengaged. In this case the liquor will appear in the course of a few weeks as if traversed with numerous crystalline colourless needles of gallic acid.

Tannin or tannic acid consists of carbon 51·56; hydrogen 4·20; oxygen 44·24.

From the above facts it is obvious that gallic acid does not exist ready formed in gall nuts, but that it is produced by the reaction of atmospheric oxygen upon the tannin of these concretions.

Gallic acid is a solid, feebly acidulous and styptic to the taste, inodorous, crystallizing in silky needles of the greatest whiteness; soluble in about 100 times its weight of cold, and in a much smaller quantity of boiling water; more soluble in alcohol than in water, but little so in sulphuric ether.

Gallic acid does not decompose the salts of protoxide of iron, but it forms, with the sulphate of the peroxide, a dark blue precipitate, much less insoluble than the tannate of iron. Gallic acid takes the oxide from the acetate and nitrate of lead, and throws down a white gallate unchangeable in the air, when it is mixed with that acetate and nitrate. It occasions no precipitate in solutions of gelatine (isinglass or glue), by which criterion its freedom from tannin is verified.

Gallic acid occurs but seldom in nature; and always united to brucine, veratrine, or lime. Its constituents are, carbon 49·89; hydrogen 3·49; oxygen 46·62. In the crystalline state it contains one atom of water, which it loses by drying.

Scheele obtained gallic acid by infusing pounded galls for 3 or 4 days in 8 times their weight of water, and exposing the infusion to the air, in a vessel covered loosely with paper. At the end of two months, the liquor had almost all evaporated, leaving some mouldiness mixed with a crystalline precipitate. The former being removed, the deposit was squeezed in a linen cloth, and then treated with boiling water. The solution being gradually evaporated, yielded crystals of gallic acid, granular or star-like, of a grayish colour. These crystals might be whitened by boiling their solution along with a little animal charcoal. About one fifth of gallic acid may be obtained by Scheele’s process from good gall-nuts.

From a decoction of 500 parts of galls, Sir H. Davy obtained 185 parts of solid extract; which consisted of 130 parts of tannin; 31 parts of gallic acid with extractive; 13 parts of mucilage; 12 parts of lime and salts. Hence gall-nuts would seem to contain, by this statement, more than two-thirds of their weight of tannin. This result is now seen, from the above experiments of Pelouze, to have been incorrect, in consequence of the admixture of yellow extractive in Davy’s tannin.

The uses of galls in many processes of dyeing, and in making black ink, are detailed under their respective heads.

GALL OF ANIMALS, or OX-GALL, purification of. Painters in water colours, scourers of clothes, and many others employ ox-gall or bile, but when it is not purified, it is apt to do harm from the greenness of its own tint. It becomes therefore an important object to clarify it, and to make it limpid and transparent like water. The following process has been given for that purpose. Take the gall of newly killed oxen, and after having allowed it to settle for 12 or 15 hours in a basin, pour the supernatant liquor off the sediment into an evaporating dish of stone ware, and expose it to a boiling heat in a water bath, till it is somewhat thick. Then spread it upon a dish, and place it before a fire till it becomes nearly dry. In this state it may be kept for years in jelly pots covered with paper, without undergoing any alteration. When it is to be used, a piece of it of the size of a pea is to be dissolved in a table spoonful of water.

Another and probably a better mode of purifying ox-gall is the following. To a pint of the gall boiled and skimmed, add one ounce of fine alum in powder, and leave the mixture on the fire till the alum be dissolved. When cooled, pour into a bottle, which is to be loosely corked. Now take a like quantity of gall also boiled and skimmed, add an ounce of common salt to it, and dissolve with heat; put it when cold into a bottle, which is likewise to be loosely corked. Either of these preparations may be kept for several years without their emitting a bad smell. After remaining three months, at a moderate temperature, they deposit a thick sediment, and become clearer, and fit for ordinary uses, but not for artists in water colours and miniatures, on account of their yellowish-green colour. To obviate this inconvenience, each of the above liquors is to be decanted apart, after they have become perfectly settled, and the clear portion of both mixed together in equal parts. The yellow colouring matter still retained by the mixture coagulates immediately and precipitates, leaving the ox-gall perfectly purified and colourless. If wished to be still finer, it may be passed through filtering paper; but it becomes clearer with age, and never acquires a disagreeable smell, nor loses any of its good qualities.

Clarified ox-gall combines readily with colouring matters or pigments, and gives them solidity either by being mixed with or passed over them upon paper. It increases the brilliancy and the durability of ultramarine, carmine, green, and in general of all delicate colours, whilst it contributes to make them spread more evenly upon the paper, ivory, &c. When mixed with gum Arabic, it thickens the colours without communicating to them a disagreeable glistering appearance; it prevents the gum from cracking, and fixes the colours so well that others may be applied over them without degradation. Along with lamp black and gum, it forms a good imitation of China ink. When a coat of ox-gall is put upon drawings made with black lead or crayons, the lines can no longer be effaced, but may be painted over safely with a variety of colours previously mixed up with the same ox-gall.

Miniature painters find a great advantage in employing it; by passing it over ivory, it removes completely the unctuous matter from its surface; and when ground with the colours, it makes them spread with the greatest ease, and renders them fast.

It serves also for transparencies. It is first passed over the varnished or oiled paper, and is allowed to dry. The colours mixed with the gall are then applied, and cannot afterwards be removed by any means.

It is adapted finally for taking out spots of grease and oil.

GALL OF GLASS, called also sandiver, is the neutral salt skimmed off the surface of melted crown glass; which, if allowed to remain too long, is apt to be reabsorbed in part, and to injure the quality of the metal, as the workmen call it.

GALVANIZED IRON, is the somewhat fantastic name newly given in France to iron tinned by a peculiar patent process, whereby it resists the rusting influence of damp air, and even moisture, much longer than ordinary tin plate. The following is the prescribed process. Clean the surface of the iron perfectly by the joint action of dilute acid and friction, plunge it into a bath of melted zinc, and stir it about till it be alloyed superficially with this metal; then take it out, and immerse it in a bath of tin, such as is used for making tin plate. The tin forms an exterior coat of alloy. When the metal thus prepared is exposed to humidity, the zinc is said to oxidize slowly by a galvanic action, and to protect the iron from rusting within it, whereby the outer tinned surface remains for a long period perfectly white, in circumstances under which iron tinned in the usual way would have been superficially browned and corroded with rust.

GAMBOGE; (Gomme Gutte, Fr.; Gutti, Germ.) is a gum resin, concreted in the air, from the milky juice which exudes from several trees. The gambogia gutta, a tree which grows wild upon the coasts of Ceylon and Malabar, produces the coarsest kind of gamboge; the guttaefera vera (Stalagmites cambogioides) of Ceylon and Siam affords the best. It comes to us in cylindrical lumps, which are outwardly brown yellow, but reddish yellow within, as also in cakes; it is opaque, easily reducible to powder, of specific gravity 1·207, scentless, and nearly devoid of taste, but leaves an acrid feeling in the throat. Its powder and watery emulsion are yellow. It consists of 80 parts of a hyacinth red resin, soluble in alcohol; and 20 parts of gum; but by another analysis, of 89 of resin, and 10·5 of gum. Gamboge is used as a pigment, and in miniature painting, to tinge gold varnish; in medicine as a powerful purge. It should never be employed by confectioners to colour their liqueurs, as they sometimes do.

GANGUE. A word derived from the German gang, a vein or channel. It signifies the mineral substance which either encloses or usually accompanies any metallic ore in the vein. Quartz, lamellar carbonate of lime, sulphate of baryta, sulphate and fluate of lime, generally form the gangues; but a great many other substances become such when they predominate in a vein. In metallurgic works the first thing is to break the mixed ore into small pieces, in order to separate the valuable from the useless parts, by processes called stamping, picking, sorting. See METALLURGY and MINES.

GARNET (Grenat, Fr.; Granat, Germ.); is a vitreous mineral of the cubic system, of which the predominating forms are the rhomboidal dodecahedron and the trapœzohedron; specific gravity varying from 3·35 to 4·24; fusible at the blowpipe. Its constituents are, silica, 42; alumina, 20·0; lime, 34·0; protoxide of iron, 4. Garnets are usually disseminated, and occur in all the primitive strata from gneiss to clay slate. The finer varieties, noble garnet or Almandine, and the reddish varieties of Grossulaire (Essonite), are employed in jewellery; the first are called the Syrian or oriental; the others, hyacinth. In some parts of Germany garnets are so abundant as to be used as fluxes to some iron ores; in others, the garnet gravel is washed, pounded, and employed as a substitute for emery. The garnets of Pegu are most highly valued. Factitious garnets may be made by the following composition:--Purest white glass, 2 ounces; glass of antimony, 1 ounce; powder of cassius, 1 grain; manganese, 1 grain.

GAS (Eng. and Fr.; Gaz, Germ.); is the generic name of all those elastic fluids which are permanent under a considerable pressure, and at the temperature of zero of Fahrenheit. In many of them, however, by the joint influence of excessive cold and pressure, the repulsive state of the particles may be balanced or subverted, so as to transform the elastic gas into a liquid or a solid. For this most interesting discovery, we are indebted to the fine genius of Mr. Faraday.

The following table exhibits the temperatures and pressures at which certain gases are liquefied.

+---------------------+--------------------------+-------------------+ | | Becomes liquid | Calculated | | Name of the gas. +------+-------------------+ boiling point; | | | At |Under a pressure of|Barom. = 30 inches.| +---------------------+------+-------------------+-------------------+ |Sulphurous acid |59° F.| 3 atmospheres. | - 4° Fahr. | |Chlorine |60 | 4 | - 22 | |Ammonia |50 | 6·5 | - 64 | |Sulphuretted hydrogen|50 | 17 | - 142 | |Carbonic acid |32 | 36 | - 229 | |Hydrochloric or | | | | |muriatic acid |50 | 50 | - 249 | |Deutoxide of azote |45 | 50 | - 254 | +---------------------+------+-------------------+-------------------+

Liquid carbonic acid becomes solidified, into a snowy-looking substance, by its own rapid evaporation. Oxygen, hydrogen, and azote, have hitherto resisted all attempts to divest them of their elastic form. For this purpose, it is probable that a condensing force equal to that of 650 atmospheres, will be required.

The volume of any gas is, generally speaking, inversely as the pressure to which it is exposed; thus, under a double pressure its bulk becomes one-half; under a triple pressure, one-third; and so on. For the change of volume in gaseous bodies by heat, see EXPANSION.

Ammonia, carbonic acid, carburetted hydrogen, chlorine, muriatic acid, sulphurous acid, sulphuretted hydrogen, are the gases of most direct interest in the arts and manufactures. Their detailed examination belongs to a work on chemistry.

GAS-LIGHT. (Eclairage par gas, Fr.; Gaslicht, Germ.) Dr. Clayton demonstrated, by numerous experiments in 1737 and 1738, that bituminous pit-coal, subjected to a red heat in close vessels, afforded a great deal of an air similar to the fire-damp of mines, but which burned with a brighter flame. It does not appear that this species of factitious air was ever produced from pit-coal for the purpose of artificial illumination till 1792, when Mr. William Murdoch, engineer to Messrs. Bolton and Watt, employed coal gas for lighting his house and offices, at Redruth in Cornwall. The gas was generated in an iron retort, whence it was received in a gasometer, distributed in different situations by pipes, and finally burned at small apertures which could be opened and stopped at pleasure. He moreover made this light movable, by confining the gas in portable tin-plate vessels, and burning it wherever he pleased. Between this period and 1802, Mr. Murdoch continued at intervals to make similar experiments; and upon occasion of the national illumination in the spring of the latter year, at the peace of Amiens, he lighted up part of the Soho manufactory with a public display of gas lights.

The earliest application of this artificial light, on a large systematic scale, was made at Manchester; where an apparatus for lighting the great cotton mills of Messrs. Philips and Lee, was fitted up in 1804 and 1805, under the direction of Mr. Murdoch. A quantity of light, nearly equal to 3000 candles, was produced and distributed in this building. This splendid pattern has been since followed very generally in Great Britain, and more or less in many parts of the continents of Europe and America. By the year 1822, gas-lighting in London had become the business of many public companies. At the Peter-street station, for example, 300 retorts had been erected, supplying 15 gasometers, having each an average capacity of 20·626 cubic feet, but, being never quite filled, their total contents in gas might be estimated at 309,385 cubic feet. The extent of main pipes of distribution belonging to this station was then about 57 miles, with two separate mains in some of the streets. The product of gas was from 10,000 to 12,000 cubic feet from a chaldron of coals. The annual consumption of coals was therefore altogether 9282 chaldrons, affording 11,384,000 cubic feet of gas, allowing 153 retorts to be in constant daily action, upon an average of the year; and illuminating 10,660 private lamps, 2248 street lamps, and 3894 theatre lamps.

At the Brick-lane works, 371 retorts were fixed in 1822, 133 being worked on an average of summer and winter. There were 12 gasometers, charged with an average quantity of gas amounting to 197,214 cubic feet. Of coals, 8060 chaldrons were annually consumed; 96,720,000 cubic feet of gas were generated; for the supply of 1978 public lamps, and 7366 private ones, connected with main pipes 40 miles long.

At the Curtain-road gas establishment, there were 240 retorts; but the greatest number worked in 1821 was only 80, and the lowest 21. The six gasometers had an average contents of 90,467 cubic feet. Of coals, 3336 chaldrons were annually consumed, yielding 40,040,000 cubic feet of gas, that supplied 3860 private lamps, and 629 public ones, by means of mains 25 miles long. The above three stations belonged to the London Gas Light and Coke Company.

The City of London Gas Light Company, Dorset-street, had built up 230 retorts, and 6 gasometers, while two were preparing; having a total capacity of 181,282 cubic feet. Of private lamps 5423 were lighted, and 2413 public ones, from mains extending 50 miles. The quantity of coals carbonized amounted to 8840 chaldrons; producing 106,080,000 cubic feet of gas.

The South London Gas Light and Coke Company had mounted at Bankside 143 retorts, with 3 gasometers; the contents of the whole being 41,110 cubic feet, connected with mains from 30 to 40 miles long. At their other station, in Wellington-street, 3 large gasometers were then erecting, with a capacity of 73,565 cubic feet, which were to be supplied with gas from Bankside, till retorts were mounted for them.

The Imperial Gas Light and Coke Company had at that time 6 gasometers in progress at their Hackney station.

In 1822 there were thus four great companies, having in all 47 gasometers at work, capable of containing 917,940 cubic feet of gas, supplied by 1315 retorts, which generated per annum upwards of 397,000,000 cubic feet of gas, by which 61,203 private lamps, and 7268 public or street lamps, were lighted in the metropolis. Besides these public companies, there were likewise several private ones.

1. Of the generation of illuminating gases.--Pure hydrogen gas burns with too feeble a flame to be employed for illumination. But carburetted hydrogen having the property of precipitating its carbon in the act of burning, its solid particles become incandescent, and diffuse a vivid light. The more carbon it contains, the more brightly does it burn. This gas exists in two distinct states of combination. In the first, two measures of hydrogen gas are combined with one measure of the vapour of carbon, forming together one measure whose specific gravity is of course the sum of the weights of the constituents, or 0·559; atmospherical air being 1·000. This is the gas which is found in mines, and is also evolved in ditches from decomposing vegetable matter. In the second, two measures of hydrogen gas are combined with two of gaseous carbon, forming also one volume or measure whose weight or specific gravity is 0·985. This was at one time called the olefiant gas, because when mixed with chlorine an oily looking compound was produced. It may be called as well oil gas, because it is generated in considerable quantities by the igneous decomposition of oil. Thus the olefiant gas contains in the same volume double the quantity of carbon of common carburetted hydrogen, and it burns with a proportionably brighter flame. The gaseous oxide of carbon, as well as sulphuretted hydrogen gas, burns with a feeble blue light, but the latter produces in combustion sulphurous acid, an offensive and noxious gas.

By dry distillation or carbonization in close vessels, all bodies of vegetable and animal origin disengage carburetted hydrogen gas; even charcoal when placed in ignition in contact with steam, by decomposing the water, produces abundance of carbonic acid, carburetted hydrogen, hydrogen, and carbonic oxide. After separating the carbonic acid with lime water, that mixed gas contains in 100 measures, 20 of carburetted hydrogen; the rest being hydrogen and carbonic oxide, so that the gaseous mixture cannot be used for illumination. The best substances for furnishing a gas rich in luminifereous materials are, pitcoal, especially the cannel coal, resin, oil, fats of all kinds, tar, wax, &c. In some cases the gases evolved during the igneous decomposition of bones and other animal matters for the production of ammonia, may be employed for procuring light, but they are apt to emit a fetid odour.

When coals are heated in a cast-iron retort to ignition, the progress of decomposition is as follows. First, and before the retort becomes red hot, steam issues along with the atmospheric air. When the retort begins to redden, tar distils in considerable quantity with some combustible gas, of which hydrogen mixed with ammoniacal gas forms a part. The evolution of gas increases as the retort becomes hotter, with a continual production of tar and ammoniacal liquor as well as sulphurous acid from the pyrites of the coal, which unites with the ammonia. When the retort has come to a bright cherry red heat, the disengagement of gas is most active. By and bye the gaseous production diminishes, and eventually ceases entirely, although the heat be increased. In the retort a quantity of carbonized coal or coke remains, while tar is found at the bottom of the receiver, covered with the ammoniacal liquor, and combined with carbonic and sulphurous acids, and sulphuretted hydrogen.

If during this distillation, the combustible gas be collected and examined at the several stages of the process, it is found to differ extremely in its luminiferous powers. That which comes off before the retort has acquired its proper temperature, gives a feeble light, and resembles the gas obtained by the ignition of moist charcoal, consisting chiefly of hydrogen. That evolved when the retort has just acquired throughout a vivid red heat, is the best of all, consisting chiefly of bicarburetted hydrogen or olefiant gas. From good coal, it consists, for example in 100 measures, of 13 of olefiant gas, 82·5 of carburetted hydrogen, 3·2 carbonic oxide, 1·3 azote; the mixture having a specific gravity of 0·650. At a later period, as after 5 hours, it contains 7 measures of olefiant gas, 56 of carburetted hydrogen, 11 of carbonic oxide, 21·3 of hydrogen, 4·7 of azote; the specific gravity of the whole being 0·500. Towards the end of the operation, as after 10 hours, it contains twenty measures of carburetted hydrogen, 10 of carbonic oxide, 60 of hydrogen, 10 of azote, with a specific gravity of only 0·345. The hydrogen becomes sulphuretted hydrogen, if there be much pyritous matter in the coal. The larger proportion of the gas is disengaged during the first hour, amounting to about one fifth of the whole; in the three following hours the disengagement is tolerably uniform, constituting in all fifty-four hundredths; in the sixth hour, it is one tenth; in the seventh and eighth hours, sixteen hundredths.

From these observations are derived the rules for the production of a good light gas from coals. They show that the distillation should commence with a retort previously heated to a cherry red, since thereby good gas is immediately produced, and a portion of the tar is also converted into gas, instead of being simply distilled over into the condenser pit; that this heat should be steadily continued during the whole operation, from 5 to 8 hours; that it should not be increased, especially towards the end, for fear of generating carbonic oxide and hydrogen gases, as well as of injuring the retort when the cooling agency of gasefication has become feeble; and that the operation should be stopped some time before gas ceases to come over, lest gases with feeble illuminating power should impoverish the contents of the gasometer. Upon the average, a pound of good coal affords four cubic feet of gas, or a chaldron = 26 cwt. London measure, affords from 12,000 to 15,000 cubic feet, according to the form of the retort, and the manner of firing it.

When oil, fats, rosin, tar, &c. are employed for the production of a light gas, it is not sufficient to introduce these substances into the retorts, and to heat them, as is done with coals. In this case, the greater part of them would distil over in the state of volatile oils, and very little gas be generated, only as much as corresponded to the quantity of fat, &c. in immediate contact with the retort. It becomes therefore necessary to fill the retorts with pieces of brick or coke; and to keep them in ignition, while the oil, &c. is slowly introduced into their interior. The fats instantly assume the vaporous state, and thus coming into contact upon an extensive surface with the ignited bricks, are decomposed into combustible gases. A small portion of carbonaceous matter remains in the retort, while much olefiant gas is formed, possessing a superior illuminating power to common coal gas, and entirely free from sulphureous impregnation. The best oil gas is generated at a dull red, a heat much below what is requisite for the decomposition of coal. A more intense heat would indeed produce a greater volume of gas, but of a poorer quality, because the olefiant gas thereby deposits one half of its carbon, and is converted into common carburetted hydrogen. Oil affords at a lively red heat, gases which contain in 100 measures, 19 of olefiant gas, 32·4 of carburetted hydrogen, 12·2 of carbonic oxide gas, 32·4 of hydrogen, and 4 of azote; the mean specific gravity being only 0·590. At a more moderate temperature it yields 22·5 of the olefiant, 50·3 carburetted hydrogen, 15·5 carbonic oxide, 7·7 hydrogen, and 4 azote, with a specific gravity of 0·758. It contains when generated by dull ignition, as is usual in works on the manufacturing scale, in 100 parts, from 38 to 40 of olefiant gas, and besides the carburetted hydrogen, a few per cents. of carbonic oxide and azote, with a specific gravity of 0·900, and even upwards. One pound of oil or fluid fat affords 15 cubic feet of gas; of tar affords about 12 cubic feet; of rosin or pitch, 10 cubic feet.

When the oil gas is compressed by a force of from 15 to 20 atmospheres, as was the practice of the Portable Gas Company, about one fifth of the volume of the gas becomes liquefied into an oily, very volatile fluid, having the specific gravity 0·821. It is a mixture of three fluids (consisting of carburetted hydrogen), of different degrees of volatility. The most volatile of these boils even under 32° F. Some of the vapour of this gas-oil is mixed with the olefiant gas in the general products of decomposition; in consequence of which they are sometimes richer in carbon than even olefiant gas, and have a higher illuminating power. Oil gas contains about 22 per cent. and coal gas about 3-1/4 per cent. of this oily vapour. In the estimations of the composition of the gases given above, this vapour is included under olefiant gas. This vapour combines readily with sulphuric acid, and is thus precipitated from the gaseous mixture. The amount of olefiant gas is shown, by adding to the gas, contained over water, one half of its volume of chlorine, which, in the course of an hour or two, condenses the olefiant gas into an oily looking liquid (chloride of hydrocarbon.) After the mixture, the gases must be screened from the light, otherwise the common carburetted hydrogen would also combine with the chlorine, while water and carbonic acid would make their appearance.

The oil employed for affording gas is the crudest and cheapest that can be bought; even the blubber and sediment of whale oil are employed with advantage. After all, however, coal is so much cheaper, and the gas produced from it is now so well purified, that oil and rosin are very little used in gas apparatus.

Apparatus for Coal Gas.--Coal gas, as it issues from the retort, cannot be directly employed for illumination; for it contains vapours of tar and coal oil, as also steam impregnated with the carbonate, sulphite, and hydrosulphuret of ammonia. These vapours would readily condense in the pipes through which the gas must be distributed, and would produce obstructions; they must therefore be so far removed by previous cooling, as to be liable to occasion no troublesome condensation at ordinary temperatures. The crude coal gas contains moreover sulphuretted hydrogen, whose combustion for light would exhale an offensive sulphureous odour, that ought to be got rid of as much as possible. Carbonic acid and carbonic oxide gases, generated at first from the decomposition of the steam by the ignited coal, enfeeble the illuminating power of the gas, and should be removed. The disengagement of gas in the retorts is never uniform, but varies with the degree of heat to which they are exposed; for which reason the gas must be received in a gasometer, where it may experience uniform pressure, and be discharged uniformly into the pipes of distribution, in order to ensure a steady discharge of gas, and uniform intensity of light in the burners. A coal gas apparatus ought therefore to be so constructed as not only to generate the gas itself, but to fulfil the above conditions.

In fig. 482., such an apparatus is represented, where the various parts are shown connected with each other, in section.

A is the furnace with its set of cylindrical or elliptical retorts, five in number. From each of these retorts, a tube b proceeds perpendicularly upwards, and then by a curve or saddle-tube, it turns downwards, where it enters a long horizontal cylinder under B, shut at each end with a screw cap, and descends to beneath its middle, so as to dip about an inch into the water contained in it. From one end of this cylinder the tube d passes downwards, to connect itself with a horizontal tube which enters into the tar pit or cistern C, by means of the vertical branch f. This branch reaches to near the bottom of the cylindrical vessel, which sits on the sole of the tar cistern. From the other side of the vertical branch f, the main pipe proceeds to the condenser D, and thence by the pipe l, into the purifier E; from which the gas is immediately transmitted by the pipe p into the gasometer F.

The operation proceeds in the following way:--As soon as gas begins to be disengaged from the ignited retort, tar and ammoniacal liquor are deposited in the cylindrical receiver B, and fill it up till the superfluity runs over by the pipe d, the level being constantly preserved at the line shown in the figure. By the same tarry liquid, the orifices of the several pipes b, issuing from the retorts, are closed; whereby the gas in the pipe d has its communication cut off with the gas in the retorts. Hence if one of the retorts be opened and emptied, it remains shut off from the rest of the apparatus. This insulation of the several retorts is the function of the pipe under B, and therefore the recurved tube b must be dipped as far under the surface of the tarry liquid, as to be in equilibrio with the pressure of the gas upon the water in the purifier. The tube b is closed at top with a screw cap, which can be taken off at pleasure, to permit the interior to be cleansed.

Both by the overflow from the receiver-pipe B, and by subsequent condensation in the tube d, tar and ammoniacal liquor collect progressively in the cistern or pit under C, by which mingled liquids the lower orifice of the vertical tube f is closed, so that the gas cannot escape into the empty space of this cistern. These liquids flow over the edges of the inner vessel when it is full, and may, from time to time, be drawn off by the stopcock at the bottom of the cistern.

Though the gas has, in its progress hitherto, deposited a good deal of its tarry and ammoniacal vapours, yet, in consequence of its high temperature, it still retains a considerable portion of them, which must be immediately abstracted, otherwise the tar would pollute the lime in the vessel E, and interfere with its purification. On this account the gas should, at this period of the process, be cooled as much as possible, in order to condense these vapours, and to favour the action of the lime in the purifier E, upon the sulphuretted hydrogen, which is more energetic the lower the temperature of the gas. The coal gas passes, therefore, from the tube f into the tube h of the condenser D, which is placed in an iron chest g filled with water, and it deposits more tar and ammoniacal liquor in the under part of the cistern at t, t. When these liquids have risen to a certain level, they overflow into the tar-pit, as shown in the figure, to be drawn off by the stopcock as occasion may require.

The refrigerated gas is now conducted into the purifier E, which is filled with milk of lime, made by mixing one part of slaked lime with 25 parts of water. The gas, as it enters by the pipe l, depresses the water in the wide cylinder n, thence passes under the perforated disc in the under part of that cylinder, and rising up through innumerable small holes is distributed throughout the lime liquid in the vessel m. By contact with the lime on this extended surface, the gas is stripped of its sulphuretted hydrogen and carbonic acid, which are condensed into the hydro-sulphuret and carbonate of lime; it now enters the gasometer F in a purified state, through the pipe p t, and occupies the space q. The gasometer, pressing with a small unbalanced force over the counterweight s, expels it through the main u u, in communication with the pipes of distribution through the buildings or streets to be illuminated.

The parts A B C D E and F, of which this apparatus consists, are essential constituents of every good coal-gas work. Their construction rests upon peculiar principles, is susceptible of certain modifications, and therefore deserves to be considered in detail.

The Retorts.--These are generally made of cast iron, though they have occasionally been made of baked clay, like common earthenware retorts. The original form was a cylinder, which was changed to an ellipse, with the long axis in a horizontal direction, then into the shape of the letter D with the straight line undermost, and lastly into a semi-cylinder, with its horizontal diameter 22 inches, and its vertical varying from 9 to 12. The kidney form was at one time preferred, but it has been little used of late.

The form of retort represented in fig. 483. has been found to yield the largest quantity of good gas in the shortest time, and with the least quantity of firing. The length is 7-1/2, and the transverse area, from one foot to a foot and a half square. The arrows show the direction of the flame and draught in this excellent bench of retorts, as mounted by Messrs. Barlow.

The charge of coals is most conveniently introduced in a tray of sheet iron, made somewhat like a grocer’s scoop, adapted to the size of the retort, which is pushed home to its further end, inverted so as to turn out the contents, and then immediately withdrawn.

The duration of the process, or the time of completing a distillation, depends upon the nature of the coal and the form of the retort. With cylindrical retorts it cannot be finished in less than 6 hours, but with elliptical and semi-cylindrical retorts, it may be completed in 4 or 5 hours. If the distillation be continued in the former for 8 hours, and in the latter for 6, gas will continue to be obtained, but during the latter period of the operation, of indifferent quality.

The Receiver.--If the furnace contains only 2 or 3 retorts, a simple cylindrical vessel standing on the ground half filled with water, may serve as a receiver; into which the tube from the retort may be plunged. It should be provided with an overflow pipe for the tar and ammoniacal liquor. For a range of several retorts, a long horizontal cylinder is preferable, like that represented at B in fig. 484. Its diameter is from 10 to 15 inches. This cylinder may be so constructed as to separate the tar from the ammoniacal liquor, by means of a syphon attached to one of its ends.

The Condenser.--The condenser, represented in fig. 482., consists of a square chest, g, made of wrought iron plates open at top, but having its bottom pierced with a row of holes, to receive a series of tubes. To these holes the upright four-inch tubes h h are secured by flanges and screws, and they are connected in pairs at top by the curved or saddle tubes. The said bottom forms the cover of the chest t, t, which is divided by vertical iron partitions, into half as many compartments as there are tubes.

These partition plates are left open at bottom, so as to place the liquids of each compartment in communication. Thereby the gas passes up and down the series of tubes, in proceeding from one compartment to another. The condensed liquids descend into the box t, t, and flow over into the tar cistern, when they rise above the level t, t. The tar may be drawn off from time to time by the stopcock. Through the tube k, cold water flows into the condenser chest, and the warm water passes away by a pipe at its upper edge.

The extent of surface which the gas requires for its refrigeration before it is admitted into the washing-lime apparatus, depends upon the temperature of the milk of lime, and the quantity of gas generated in a certain time.

It may be assumed as a determination sufficiently exact, that 10 square feet of surface of the condenser can cool a cubic foot of gas per minute to the temperature of the cooling water. For example, suppose a furnace or arch with 5 retorts of 150 pounds of coal each, to produce in 5 hours 3000 cubic feet of gas, or 10 cubic feet per minute, there would be required, for the cooling surface of the condenser, 100 square feet = 10 × 10. Suppose 100,000 cubic feet of gas to be produced in 24 hours, for which 8 or 9 such arches must be employed, the condensing surface must contain from 800 to 900 square feet.

The Purifier.--The apparatus represented in the preceding figure is composed of a cylindrical iron vessel, with an air-tight cover screwed upon it, through which the cylinder n is also fixed air-tight. The bottom of this cylinder spreads out like the brim of a hat, forming a horizontal circular partition, which is pierced with holes. Through a stuffing box, in the cover of this interior cylinder, the vertical axis of the agitator passes, which is turned by wheel and pinion work, in order to stir up the lime from the bottom of the water in the purifier. The vessel o serves for introducing fresh milk of lime, as also for letting it off by a stopcock when it has become too foul for further use.

The quantity of lime should be proportioned to the quantity of sulphuretted hydrogen and carbonic acid contained in the gas. Supposing that in good coal gas there is 5 per cent. of these gases, about one pound and a half of lime will be requisite for every hundred cubic feet of coal gas generated, which amounts to nearly one-sixteenth of the weight of coal subjected to decomposition. This quantity of lime mixed with the proper quantity of water will form about a cubic foot of milk of lime. Consequently, the capacity of the purifier, that is, of the interior space filled with liquid, may be taken at four-sevenths of a cubic foot for every hundred cubic feet of gas passing through it in one operation; or for 175 cubic feet of gas, one cubic foot of liquor. After every operation, that is, after every five or six hours, the purifier must be filled afresh. Suppose that in the course of one operation 20,000 cubic feet of gas pass through the machine, this should be able to contain 20,000/175 = 114 cubic feet of milk of lime; whence its diameter should be seven feet, and the height of the liquid three feet. If the capacity of the vessel be less, the lime milk must be more frequently changed.

In some of the large gas works of London the purifier has the following construction, whereby an uninterrupted influx and efflux of milk of lime takes place. Three single purifiers are so connected together, that the second vessel stands higher than the first, and the third than the second; so that the discharge tube of the superior vessel, placed somewhat below its cover, enters into the upper part of the next lower vessel; consequently, should the milk of lime in the third and uppermost vessel rise above its ordinary level, it will flow over into the second, and thence in the same way into the first; from which it is let off by the eduction pipe. A tube introduces the gas from the condenser into the first vessel, another tube does the same thing for the second vessel, &c., and the tube of the third vessel conducts the gas into the gasometer. Into the third vessel, milk of lime is constantly made to flow from a cistern upon a higher level. By this arrangement, the gas passing through the several vessels in proportion as it is purified, comes progressively into contact with purer milk of lime, whereby its purification becomes more complete. The agitator c, provided with two stirring paddles, is kept in continual rotation. The pressure which the gas has here to overcome is naturally three times as great as with a single purifier of like depth.

Fig. 485. is a simple form of purifier, which has been found to answer well in practice. Through the cover of the vessel A B, the wide cylinder e d is inserted, having its lower end pierced with numerous holes. Concentric with that cylinder is the narrower one s z, bound above with the flange a b, but open at top and bottom. The under edge g h of this cylinder descends a few inches below the end c d of the outer one. About the middle of the vessel the perforated shelf m n is placed. The shaft of the agitator l, passes through a stuffing box upon the top of the vessel. The gas-pipe g, proceeding from the condenser, enters through the flange a b in the outer cylinder, while the gas-pipe h goes from the cover to the gasometer. A stopcock upon the side, whose orifice of discharge is somewhat higher than the under edge of the outer cylinder, serves to draw off the milk of lime. As the gas enters through the pipe g into the space between the two cylinders, it displaces the liquor till it arrives at the holes in the under edge of the outer cylinder, through which, as well as under the edge, it flows, and then passes up through the apertures of the shelf m n into the milk of lime chamber; the level of which is shown by the dotted line. The stirrer, l, should be turned by wheel work, though it is here shown as put in motion by a winch handle.

In order to judge of the degree of purity of the gas after its transmission through the lime machine, a slender syphon tube provided with a stopcock may have the one end inserted in its cover, and the other dipped into a vessel containing a solution of acetate of lead. Whenever the solution has been rendered turbid by the precipitation of sulphuret of lead, it should be renewed. The saturated and fetid milk of lime is evaporated in oblong cast-iron troughs placed in the ash-pit of the furnaces, and the dried lime is partly employed for luting the apparatus, and partly disposed of for a mortar or manure.

By this purifier, and others of similar construction, the gas in the preceding parts of the apparatus, as in the retorts and the condenser, suffers a pressure equal to a column of water about two feet high; and in the last described purifier even a greater pressure. This pressure is not disadvantageous, but is of use in two respects; 1. it shows by a brisk jet of gas when the apparatus is not air-tight, and it prevents common air from entering into the retorts; 2. this compression of the gas favours the condensation of the tar and ammoniacal liquor. The effect of such a degree of pressure in expanding the metal of the ignited retorts is quite inconsiderable, and may be neglected. Two contrivances have, however, been proposed for taking off this pressure in the purifier.

In fig. 486., m m are two similar vessels of a round or rectangular form, furnished at their upper border with a groove filled with water, into which the under edge of the cover fits, so as to make the vessel air-tight. The cover is suspended by a cord or chain, which goes over a pulley, and may be raised or lowered at pleasure. The vessels themselves have perforated bottoms, r r´, covered with wetted moss or hay sprinkled over with slaked and sifted quicklime. The gas passes through the loosely compacted matter of the first vessel, by entering between its two bottoms, rises into the upper space t, thence it proceeds to the second vessel, and, lastly, through the pipe u into the gasometer. This method, however, requires twice as much lime as the former, without increasing the purity of the gas.

The second method consists in compressing the gas by the action of an Archimedes screw, to such a degree, before it is admitted into the purifier, as that it may overcome the pressure of the column of water in that vessel. Fig. 487. exhibits this apparatus in section. D D is the Archimedes worm, the axis of which revolves at bottom upon the gudgeon e; it possesses a three-fold spiral, and is turned in the opposite direction to that in which it scoops the water. The cistern which contains it has an air-tight cover. The gas to be purified passes through the pipe C into the space D, over the water level d; the upper cells of the worm, scoop in the gas at this point, and carry it downwards, where it enters at g into the cavity E of a second cistern. In order that the gas, after it escapes from the bottom of the worm, may not partially return through g into the cavity D, an annular plate g h is attached to its under edge, so as to turn over it. The compressed gas is conducted from the cavity E through the pipe G into the purifying machine; a is a manometer, to indicate the elastic tension of the gas in D. On the top of the worm a mechanism is fitted for keeping it in constant rotation.

A perfect purification of light-gas from sulphuretted hydrogen, either by milk of lime or a solution of the green sulphate of iron, is attended with some difficulty, when carried so far as to cause no precipitation of sulphuret in acetate of lead, because such a degree of washing is required as is apt to diminish its illuminating power, by abstracting the vapour of the rich oily hydrocarburet which it contains. Moreover, the coal gas obtained towards the end of the distillation contains some sulphuret of carbon, which affords sulphurous acid on being burned, and can be removed by no easy method hitherto known. The lime in the purifier disengages from the carbonate and hydrosulphuret of ammonia carried over with the gas, especially when it has been imperfectly cooled in the condenser, a portion of ammoniacal gas, which, however, is not injurious to its illuminating power. The best agent for purifying gas would be the pyrolignite of lead, were it not rather expensive, because it would save the trouble of stirring, and require a smaller and simpler apparatus.

The Gasometer.--The gasometer serves not merely as a magazine for receiving the gas when it is purified, and keeping it in store for use, but also for communicating to the gas in the act of burning such an uniform pressure as may secure a steady unflickering flame. It consists of two essential parts; 1. of an under cistern, open at top and filled with water; and 2. of the upper floating cylinder or chest, which is a similar cistern inverted, and of somewhat smaller dimensions, called the gas-holder: see F, fig. 482. The best form of this vessel is the round or cylindrical; both because under equal capacity it requires least surface of metal, and it is least liable to be warped by its own weight or accidents. Since a cylindrical body has the greatest capacity with a given surface when its height is equal to its semi-diameter, its dimensions ought to be such that when elevated to the highest point in the water, the height may be equal to the radius of the base. For example, let the capacity of the gas-holder in cubic feet be k, the semi-diameter of its base be x, the height out of the water be h; h is = x = ∛(k/3·14). This height may be increased by one or two feet, according to its magnitude, to prevent the chance of any gas escaping beneath its under edge, when it is raised to its highest elevation in the water.

The size of the gasometer should be proportional to the quantity of gas to be consumed in a certain time. If 120,000 cubic feet be required, for instance, in 10 hours for street illumination, and if the gas retorts be charged four times in 24 hours, 30,000 cubic feet of gas will be generated in 6 hours. Hence the gasometer should have a capacity of at least 70,000 cubic feet, supposing the remaining 50,000 cubic feet to be produced during the period of consumption. If the gasometer has a smaller capacity, it must be supplied from a greater number of retorts during the lighting period, which is not advantageous, as the first heating of the supernumerary retorts is wasteful of fuel. Some engineers consider that a capacity of 30,000 cubic feet is the largest which can with propriety be given to a gasometer; in which case, they make its diameter 42 feet, and its height 23. When the dimensions are greater, the sheet iron must be thicker and more expensive; and the hollow cylinder must be fortified by strong internal cross braces.

The water cistern is usually constructed in this country with cast-iron plates bolted together, and made tight with rust-cement.

In cases where the weight of water required to fill such a cistern might be inconvenient to sustain, it may be made in the form represented in fig. 488.; which, however, will cost nearly twice as much. Parallel with the side of the cistern, a second cylinder C, of the same shape but somewhat smaller, is fixed in an inverted position to the bottom of the first, so as to leave an annular space B B between them, which is filled with water, and in which the floating gasometer A plays up and down. The water must stand above the cover of the inverted cylinder. a and b are the pipes for leading the gas in and out. Through an opening in the masonry upon which the gasometer apparatus rests, the space C may be entered, in order to make any requisite repairs.

The water cistern may also be sunk in the ground, and the sides made tight with hydraulic mortar, as is shown in fig. 489., and to make it answer with less water, a concentric cylindrical mass of masonry may be built at a distance of 2 or 3 inches within it.

Every large gasometer must be strengthened interiorly with cross iron rods, to stiffen both its top and bottom. The top is supported by rods stretching obliquely down to the sides, and to the under edge an iron ring is attached, consisting of curved cast-iron bars bolted together; with which the oblique rods are connected by perpendicular ones. Other vertical rods stretch directly from the top to the bottom edge. Upon the periphery of the top, at the end of the rods, several rings are made fast, to which the gas-holder is suspended, by means of a common chain which runs over a pulley at the centre. Upon the other end of the chain there is a counterpoise, which takes off the greater part of the weight of the gas-holder, leaving only so much as is requisite for the expulsion of the gas. The inner and outer surfaces of the gas-holder should be a few times rubbed over with hot tar, at a few days’ interval between each application. The pulley must be made fast to a strong frame.

If the water cistern be formed with masonry, the suspension of the gas-holder may be made in the following way. A A, fig. 489., is a hollow cylinder of cast iron, standing up through the middle of the gasometer, and which is provided at either end with another small hollow cylinder G, open at both ends and passing through the top, with its axis placed in the axis of the gas-holder. In the hollow cylinder G, the counterweight moves up and down, with its chain passing over the three pulleys B, B, B, as shown in fig. 489. E F are the gas pipes made fast to a vertical iron rod. Should the gasometer be made to work without a counterweight, as we shall presently see, the central cylinder A A, serves as a vertical guide.

In proportion as the gas-holder sinks in the water of the cistern, it loses so much of its weight, as is equal to the weight of the water displaced by the sides of the sinking vessel; so that the gas-holder when entirely immersed, exercises the least pressure upon the gas, and when entirely out of the water, it exercises the greatest pressure. In order to counteract this inequality of pressure, which would occasion an unequal velocity in the efflux of the gas, and of course an unequal intensity of light in its flame, the weight of the chain upon which the gas-holder hangs is so adjusted as to be equal, throughout the length of its motion, to one half of the weight which the gas-holder loses by immersion. In this case, the weight which it loses by sinking into the water, is replaced by the portion of the chain which passing the pulley, and hanging over, balances so much of the chain upon the side of the counterweight; and the weight which it gains by rising out of the water, is counterpoised by the links of the chain which passing over the pulley, add to the amount of the counterweight. The pressure which the gas-holder exercises upon the gas, or that with which it forces it through the first main pipe, is usually so regulated as to sustain a column of from one to two inches of water; so that the water will stand in the cistern from one to two inches higher within, than without the gas-holder. The following computation will place these particulars in a clear light.

Let the semi-diameter of the gas-holder, equal to the vertical extent of its motion into and out of the water, = x; let the weight of a foot square of the side of the gas-holder, including that of the strengthening bars and ring, which remain plunged under the water, be = p; then

1. the weight of the gas-holder in its highest position =

3 p π _x_²;

2. the weight of the sides of the gas-holder which play in the water =

2 p π _x_²;

3. the cubic contents of the immersed portion of the gas-holder =

2 p π _x_² ------------ 400;

4. its loss of weight in water =

112 --- p π _x_²; 400

5. the weight of the gas-holder in its lowest position =

( 112) p π _x_² (3 - ---) = 2·72 p π _x_²; ( 400)

6. the weight of n inches, height of water =

56 -- n π _x_²; 12

7. the amount of the counterweight =

( 56 n) π _x_² (3 p - ------); ( 12 )

8. the weight of the chain for the length x =

112 --- p π x. 800

If we reduce the weight of the gas-holder in its highest and lowest positions to the height of a stratum of water equal to the surface of its top, this height is that of the column of water which would press the gas within the gasometer, were no counterweight employed; it consists as follows;--

9. for the highest position =

3 p -----; 56

10. for the lowest =

2·72 p --------; 50

For the case, when the height of the gas-holder is different from its semi-diameter, let this height = m x; then the height of the water level is

11. for the highest position =

(1 + 2 m) p (---------); ( 56 )

12. for the lowest =

(1 + 1·72 m) p (------------); ( 6 )

13. the counterweight =

( 56 n) π _x_² (p (1 + 2 m) - ------); ( 12 )

14. the weight of the equalizing chain =

112 --- p π m _x_². 800

For example, let the diameter of the gas-holder be 30 feet, the height 15 (the contents in cubic feet will be 10,597), p = 4 pounds; then the counterweight for a height of an inch and a half of water pressure = 3532 pounds; the weight of the chain for a length of 15 feet = 395 pounds. Were no counterweight employed, so that the gas-holder pressed with its whole weight upon the gas, then the height of the equivalent column of water in its highest position = 2·56 inches; and in its lowest, 2·33. The counterweight may hence be lessened at pleasure, if the height of the pressing water-column n be increased. The weight of the equalising or compensating portion of the chain remains the same. When n = 2 inches, for instance, the counterweight = 1886 pounds.

The velocity with which the gas passes along the mains for supplying the various jets of light, may be further regulated by opening the main-cock or slide-valve in a greater or less degree.

Gasometers whose height is greater than their semi-diameter, are not only more costly in the construction, but require heavier counterweights and equilibration chains.

The above estimate is made on the supposition of the gas in the gas-holder being of the same specific gravity as the atmospherical air, which would be nearly true with regard to oil gas under the ordinary pressure. But coal gas, whose specific gravity may be taken on an average at about 0·5, exercises a buoyancy upon the top of the gas-holder, which of course diminishes its absolute weight. Supposing the cubic foot of gas to be = 0·0364 pounds, the buoyancy will be = 0·0364 π _x_³ pounds; a quantity which deserves to be taken into account for large gasometers. Hence,

15. the weight of the gas-holder in its highest position =

3 p π _x_² - 0·1143 _x_³;

16. the counterweight =

( 56 n) π _x_² (3 p - ------) - 0·1143 _x_²; ( 12 )

17. The weight of the chain for the length x, =

112 0·1143 _x_³ --- p π _x_² --------------; 800 2

18. The height of the water pressure for the highest position, without the counterweight =

3 p π - 0·1143 x --------------------; 56 π

19. the same for the lowest position =

2·72 p -------- in feet. 56

The preceding values of p and x, are,

(16) = 3147; (17) = 203; (18) = 2·44 inches; (19) = 2·33 inches.

The water columns in the highest and lowest situations of the gas-holder here differ about 0·1 of an inch, and this difference becomes still less when p has a smaller value, for example, 3 pounds, or when the diameter of the gas-holder is still greater.

It would thus appear that for coal-gas gasometers, in which the height of the gas-holder does not exceed its semi-diameter, and especially when it has a considerable size, neither a compensation chain nor a counterweight is necessary. The only thing requisite, is to preserve the vertical motion of the gas-holder by a sufficient number of guide rods or pillars, placed either within the water cistern, or round about it. Should the pressure of the gas in the pipe proceeding from the gasometer, be less than in the gasometer itself, this may be regulated by the main valve, or by water valves of various kinds. Or a small intermediate regulating gasometer may be introduced between the great gas-holder, and the main pipe of distribution. With a diameter of 61 feet in the gas-holder, the pressure in the highest and lowest positions is the same.

The gasometers employed in storing up gas until required for use, occupy, upon the old plan, much space, and are attended with considerable expense in erecting. The water tank, whether sunk in the ground, or raised, must be of equal dimensions with the gasometer, both in breadth and depth. The improved construction which we are about to describe, affords a means of reducing the depth of the tank, dispensing with the bridge of suspension, and of increasing at pleasure the capacity of the gasometer, upon a given base; thus rendering a small apparatus capable, if required, of holding a large quantity of gas, the first cost of which will be considerably less than even a small gasometer constructed upon the ordinary plan.

Mr. Tait, of Mile-End Road, the inventor, has, we believe, been for some years connected with gas establishments, and is therefore fully aware of the practical defects or advantages of the different constructions of gasometers now in use. Fig. 490. is a section of Mr. Tait’s improved contrivance; a a is the tank, occupied with water, b b two iron columns, with pulley-wheels on the top, c c, chains attached to a ring of iron, d d, extending round the gasometer, which chains pass over the pulley-wheels, and are loaded at their extremities, for the purpose of balancing the weight of the materials of which the gasometer is composed.

The gasometer is formed by 2 or 3 cylinders, sliding one within the other, like the tubes of a telescope; e, e, e, is the first or outer cylinder, closed at the top, and having the ring of iron d, passing round it, by which the whole is suspended; f f, is the second cylinder, sliding freely within the first, and there may be a third and fourth within these if necessary.

When there is no gas in the apparatus, all the cylinders are slidden down, and remain one within the other immersed in the tank of water; but when the gas rises through the water pressing against the top of the gasometer, its buoyancy causes the cylinder e to ascend. Round the lower edge of this cylinder a groove is formed by the turning in of the plate of iron, and as it rises, the edge takes hold of the top rim of the cylinder f, which is overlapped for that purpose. The groove at the bottom of the cylinder fills itself with water as it ascends, and by the rim of the second cylinder falling into it, an air-tight hydraulic joint is produced.

Thus, several cylinders may be adapted to act in a small tank of water, by sliding one within the other, with lapped edges forming hydraulic joints, and by supporting the apparatus in the way shown, the centre of gravity will always be below the points of suspension. A gasometer may be made upon this plan of any diameter, as there will be no need of frame work, or a bridge to support it; and the increasing weight of the apparatus, as the cylinders are raised one after the other, may be counterpoised by loading the ends of the chains c c.

The water in the gasometer need not be renewed; but merely so much of it as evaporates or leaks out, is to be replaced. Indeed the surface of the water in the cistern gets covered with a stratum of coal oil, a few inches deep, which prevents its evaporation, and allows the gas to be saturated with this volatile substance, so as to increase its illuminating powers.

The gasometer may be separated from the purifier by an intermediate vessel, such as is represented fig. 491., with which the two gas pipes are connected. A is the cylindrical vessel of cast iron, a, the end of the gas pipe which comes from the purifier, immersed a few inches deep into the liquid with which the vessel is about two-thirds filled; b is the gas-pipe which leads into the gasometer, c is a perpendicular tube, placed over the bottom of the vessel, and reaching to within one-third of the top, through which the liquid is introduced into the vessel, and through which it escapes when it overflows the level d. In this tube the liquid stands towards the inner level higher, in proportion to the pressure of the gas in the gasometer. The fluid which is condensed in the gas pipe, b, and in its prolongation from the gasometer, runs off into the vessel A; and therefore the latter must be laid so low that the said tube may have the requisite declivity. A straight stop-cock may also be attached to the side over the bottom, to draw off any sediment.

II. APPLICATION OF LIGHT-GAS.

1. Distribution of the pipes.--The pressure by which the motion of the gas is maintained in the pipes, corresponds to a certain height of water in the cistern of the gasometer. From the magnitude of this pressure, and the quantity of gas which in a given time, as an hour, must be transmitted through a certain length of pipes, depends the width or the diameter that they should have, in order that the motion may not be retarded by the friction which the gas, like all other fluids, experiences in tubes, and thereby the gas might be prevented from issuing with the velocity required for the jets of flame. The velocity of the gas in the main pipe increases in the ratio of the square root of the pressing column of water upon the gasometer, and therefore by increasing this pressure, the gas may be forced more rapidly along the remoter and smaller ramifications of the pipes. Thus it happens, however, that the gas will be discharged from the orifices near the gasometer, with superfluous velocity. It is therefore advisable to lay the pipes in such a manner, that in every point of their length, the velocity of discharge may be nearly equal. This may be nearly effected as follows;--

From experiment it appears that the magnitude of the friction, or the resistance which the air suffers in moving along the pipes, under a like primary pressure, that is for equal initial velocity, varies with the square root of the length. The volume of gas discharged from the end of a pipe, is directly proportional to the square of its diameter, and inversely as the square root of its length; or, calling the length L, the diameter D, the cubic feet of gas discharged in an hour k; then k = D²/√L. Experience likewise shows, that for a pipe 250 feet long, which transmits in an hour 200 cubic feet of gas, one inch is a sufficient diameter.

Consequently,

1 D² √(k √L) 200 : k ∷ -------- : --; and D = --------- 144 √250 √L 455,000

From this formula the following table of proportions is calculated.

+---------------+---------------+----------+ |Number of cubic|Length of pipe,|Diameter, | |feet per hour. | in feet. |in inches.| +---------------+---------------+----------+ | 50 | 100 | 0·40 | | 250 | 200 | 1·00 | | 500 | 600 | 1·97 | | 700 | 1000 | 2·65 | | 1000 | 1000 | 3·16 | | 1500 | 1000 | 3·87 | | 2000 | 1000 | 4·47 | | 2000 | 2000 | 5·32 | | 2000 | 4000 | 6·33 | | 2000 | 6000 | 7·00 | | 6000 | 1000 | 7·75 | | 6000 | 2000 | 9·21 | | 8000 | 1000 | 8·95 | | 8000 | 2000 | 16·65 | +---------------+---------------+----------+

These dimensions are applicable to the case where the body of gas is transmitted through pipes without being let off in its way by burners, that is, to the mains which conduct the gas to the places where it is to be used. If the main sends off branches for burners, then for the same length the diameter may be reduced, or for like diameter the length may be greater. For example, if a pipe of 5·32 inches, which transmits 2000 cubic feet through a length of 2000 feet, gives off, in this space, 1000 cubic feet of gas; then the remainder of the pipe, having the same diameter, can continue to transmit the gas through a length of 2450 feet = (450,000/k)², with undiminished pressure for the purposes of lighting. Inversely, the diameter should be progressively reduced in proportion to the number of jets sent off in the length of the pipe.

Suppose for instance, the gasometer to discharge 2000 cubic feet per hour, and the last point of the jets to be at a distance of 4000 feet. Suppose also that from the gasometer to the first point of lighting, the gas proceeds through 1000 feet of close pipe, the diameter of the pipe will be here 4·47 inches; in the second 1000 feet of length, suppose the pipe to give off, at equal distances, 1000 cubic feet of gas, the diameter in this length (calculated at 1500 cubic feet for 1000 feet long) = 3·87 inches; in the third extent of 1000 feet, 600 cubic feet of gas will be given off, and the diameter (reckoning 700 cubic feet for 1000 feet long) will be 2·65 inches; in the fourth and last space (for 200 cubic feet in 1000 feet long) the pipe has a diameter of only an inch and a half, for which, in practice, a two-inch cast iron pipe is substituted; this being the smallest used in mains, into which branch pipes can be conveniently inserted.

The same relations hold with regard to branch pipes through which the gas is transmitted into buildings and other places to be illuminated. If such pipes make frequent angular turnings, whereby they retard the motion of the gas, they must be a third or a half larger in diameter. The smallest tubes of distribution are never less than one fourth of an inch in the bore.

Where, from one central gas work, a very great quantity of light is required in particular localities, there ought to be placed near these spots gasometers of distribution, which, being filled during the slack hours of the day, are ready to supply the burners at night, without making any considerable demand upon the original main pipe. Suppose the first main be required to supply 8000 cubic feet in the hour, for an illumination of 8 hours, at the distance of 2000 feet, a pipe 10-2/3 inches in diameter would be necessary; but if two or three gasometers of distribution, or station gasometers be had recourse to, into which the gas during the course of 24 hours would flow through the same distance continuously from the central gas works, the quantity required per hour from them would be only one third of 8000, = 2666·6 cubic feet; consequently the diameter for such a pipe is only 6·15 inches.

All the principal as well as branch pipes, whose interior diameter exceeds an inch and a half, are made of cast iron from 6 to 8 feet long, with elbow pipes cast in them where it is necessary. These pipe lengths are shown in fig. 492., having at one end a wide socket a, and at the other a nozzle b, which fits the former. After inserting the one in the other in their proper horizontal position, a coil of hemp soaked with tar is driven home at the junction; then a luting of clay is applied at the mouth, within which a ring of lead is cast into the socket, which is driven tight home with a mallet and blunt chisel.

The pipes should be proved by a force pump before being received into the gas works; two or three lengths of them should be joined before laying them down, and they should be placed at least two feet below the surface, to prevent their being affected by changes of temperature, which would loosen the joints. The tubes for internal distribution, when of small size are made of lead, copper, wrought iron, or tin.

Instead of a stopcock for letting off the gas in regulated quantities from the gasometer, a peculiarly formed water or mercurial valve is usually employed. Fig. 493. shows the mode of construction for a water trap or lute, and is, in fact, merely a gasometer in miniature. C D E F is a square cast iron vessel, in the one side of which a pipe A is placed in communication with the gasometer, and in the other, one with the main B. The movable cover or lid H G I K has a partition, L M, in its middle. If this cover be raised by its counterweight, the gas can pass without impediment from A to B; but if the counterweight be diminished so as to let the partition plate L M sink into the water, the communication of the two pipes is thereby interrupted. In this case the water-level stands in the compartment A so much lower than outside of it, and in the compartment B, as is equivalent to the pressure in the gasometer; therefore the pipes A and B must project thus far above the water. In order to keep the water always at the same height, and to prevent it from flowing into the mouths of these pipes, the rim C D of the outer vessel stands somewhat lower than the orifices A B; and thence the vessel may be kept always full of water.

If a quicksilver valve be preferred, it may be constructed as shown in fig. 494. A B are the terminations of the two gas pipes, which are made fast in the rectangular iron vessel M. E is an iron vessel of the same form, which is filled with quicksilver up to the level a, and which, by means of the screw G, which presses against its bottom, and works in the fixed female screw C C, may be moved up or down, so that the vessel M may be immersed more or less into the quicksilver. The vessel M is furnished with a vertical partition m; the passage of the gas from A to B is therefore obstructed when this partition dips into the quicksilver, and from the gradual depression of the vessel E by its screw, the interval between the quicksilver and the lower edge of the partition, through which the gas must enter, may be enlarged at pleasure, whereby the pressure of the gas in B may be regulated to any degree. The transverse section of that interval is equal to the area of the pipe or rather greater; the breadth of the vessel M from A to B amounts to the double of that space, and its length to the mere diameter of A or B. The greatest height to which the partition m can rise out of the quicksilver, is also equal to the above diameter, and in this case the line a comes to the place of b. The vertical movement of the outer vessel E, is secured by a rectangular rim or hoop which surrounds it, and is made fast to the upper part of the vessel M, within which guide it moves up and down. Instead of the lever D D, an index with a graduated plate may be employed to turn the screw, and to indicate exactly the magnitude in the opening of the valve.

In order to measure the quantity of gas which passes through a pipe for lighting a factory, theatre, &c., the gas-meter is employed, of whose construction a sufficiently precise idea may be formed from the consideration of fig. 495., which shows the instrument in a section perpendicular to its axis.

Within the cylindrical case a, there is a shorter cylinder b b, shut at both ends, and movable round an axis, which is divided into four compartments, that communicate by the opening d, with the interval between this cylinder and the outer case. The mode in which this cylinder turns round its axis is as follows:--The end of the tube c, which is made fast to the side of the case, and by which the gas enters, carries a pivot or gudgeon, upon which the centre of its prop turns; the other end of the axis runs in the cover, which here forms the side of a superior open vessel, in which, upon the same axis, there is a toothed wheel. The vessel is so far filled with water, that the tube c just rises above it, which position is secured by the level of the side vessel. When the gas enters through the tube c, by its pressure upon the partition e, (fig. 495.) it turns the cylinder from right to left upon its axis, till the exterior opening d rises above the water, and the gas expands itself in the exterior space, whence it passes off through a tube at top. At every revolution a certain volume of gas thus goes through the cylinder, proportional to its known capacity. The wheel on the axis works in other toothed wheels, whence, by means of an index upon a graduated disc or dial, placed at top or in front of the gas-meter, the number of cubic feet of gas, which pass through this apparatus in a given time, is registered.

B. Employment of the gas for lighting.--The illuminating power of different gases burned in the same circumstances, is proportional, generally speaking, to their specific gravity, as this is to the quantity of carbon they hold in combination. The following table exhibits the different qualities of gases in respect to illumination.

+-------------------+----------------------------+ | Density or |Proportion of light afforded| | specific gravity. | by coal gas to oil gas. | +----------+--------+----------------------------+ | Coal gas.|Oil gas.| | +----------+--------+ | | 0·659| 0·818 | 100 : 140 | | 0·578| 0·910 | 100 : 225 | | 0·605| 1·110 | 100 : 250 | | 0·407| 0·940 | 100 : 354 | | 0·429| 0·965 | 100 : 356 | | 0·508| 1·175 | 100 : 310 | +----------+--------+----------------------------+ |Mean 0·529| 0·96 | 100 : 272 | +----------+--------+----------------------------+

In the last three proportions, the coal gas was produced from coals of middle quality; in the first three proportions from coals of good quality; and therefore the middle proportion of 100 to 270 may be taken to represent the fair average upon the great scale. On comparing the gas from bad coals, with good oil gas, the proportion may become 100 to 300. Nay, coal gas of specific gravity 0·4, compared to oil gas of 1·1, gives the proportion of 1 to 4. A mould tallow candle, of 6 in the pound, burning for an hour, is equivalent to half a cubic foot of ordinary coal gas, and to four tenths of a foot of good gas. The flame of the best argand lamp of Carcel, in which a steady supply of oil is maintained by pump-work, consuming 42 grammes = 649 grains English in an hour, and equal in light to 9·38 such candles, is equivalent to 3·75 cubic feet of coal gas per hour. The sinumbra lamp, which consumes 50 grammes = 772 grains English, of oil per hour, and gives the light of 8 of the above candles, is equivalent to the light emitted by 3·2 cubic feet of coal gas burning for an hour. A common argand lamp, equal to 4 candles, which consumes 30 grammes = 463 grains English per hour, is represented by 1·6 cubic feet of gas burning during the same time. A common lamp, with a flat wick and glass chimney, whose light is equal to 1·13 tallow candles, and which consumes 11 grammes = 169·8 grains English per hour, is represented by 0·452 of a cubic foot of gas burning for the same time.

Construction of the Burners.--The mode of burning the gas as it issues from the jets has a great influence upon the quantity and quality of its light. When carburetted hydrogen gas is transmitted through ignited porcelain tubes, it is partially decomposed with a precipitation of some of its carbon, while the resulting gas burns with a feebler flame. Coal gas, when kindled at a small orifice in a tube, undergoes a like decomposition and precipitation. Its hydrogen, with a little of its carbon, burns whenever it comes into contact with the atmospherical air, with a bluish coloured flame; but the carbonaceous part not being so accendible, takes fire only when mixed with more air; therefore at a greater distance from the beak, and with a white light from the vivid ignition of its solid particles. Upon this principle pure hydrogen gas may be made to burn with a white instead of its usual blue flame, by dusting into it particles of lamp black; or by kindling it at the extremity of a tube containing finely pulverized zinc. The metallic particles become ignited, and impart their bright light to the pale blue flame. Even platinum wire and asbestos, when placed in the flame of hydrogen gas, serve to whiten it. Hence it has been concluded, that the intensity of light which a gas is capable of affording is proportional to the quantity of solid particles which it contains, and can precipitate in the act of burning. Carbonic oxide gas burns with the feeblest light next to hydrogen, because it deposits no carbon in the act of burning. Phosphuretted hydrogen gives a brilliant light, because the phosphoric acid, into which its base is converted during the combustion, is a solid substance, capable of being ignited in the flame. Olefiant gas, as also the vapour of hydro-carbon oil, emits a more vivid light than common coal gas; for the first is composed of two measures of hydrogen and two measures of the vapour of carbon condensed into one volume; while the last contains only one measure of the vapour of carbon in the same bulk, and combined with the same proportion of hydrogen. Olefiant gas may therefore be expected to evolve a double quantity of carbon in its flame, which should emit a double light.

The illuminating power of the flame of coal gas is, on the contrary, impaired, when, by admixture with other species of gas which precipitate no carbon, its own ignited particles are diffused over a greater surface. This happens when it is mixed with hydrogen, carbonic oxide, carbonic acid, and nitrogen gases, and the diminution of the light is proportional to the dilution of the coal gas.

In like manner the illuminating power of coal gas is impaired, when it is consumed too rapidly to allow time for the separation and ignition of its carbonaceous matter; it burns, in this case, without decomposition, and with a feeble blue flame. 1. This occurs when the light-gas is previously mixed with atmospherical air, because the combustion is thereby accelerated throughout the interior of the flame, so as to prevent the due separation of carbon. A large admixture of atmospherical air makes the flame entirely blue. 2. When it issues, with considerable velocity, from a minute orifice, whereby the gas, by expansion, gets intimately mixed with a large proportion of atmospherical air. If the jet be vertical, the bottom part of the flame is blue, and the more so the less carbon is contained in the gas. The same thing may be observed in the flame of tallow, wax, or oil lights. The burning wick acts the part of a retort, in decomposing the fatty matter. From the lower part of the wick the gases and vapours of the fat issue with the greatest velocity, and are most freely mixed with the air; while the gases disengaged from the upper part of the wick compose the interior of the flame, and being momentarily protected from the action of the atmosphere, acquire the proper high temperature for the deposition of carbon, which is then diffused on the outer surface in an ignited state, and causes its characteristic white light. Hence with coal gas, the light increases in a certain ratio with the size of the flame as it issues from a larger orifice, because the intermixture of air becomes proportionately less. 3. If by any means too great a draught be given to the flame, its light becomes feebler by the rapidity and completeness with which the gas is burned, as when too tall a chimney is placed over an argand burner, see fig. 496. Fig. 497. c, is a view of the upper plate, upon which the glass chimney b rests. The gas issues through the smaller openings of the inner ring, and forms a hollow cylindrical flame, upon the outside as well as the inside of which the atmospherical air acts. The illuminating power of this flame may be diminished at pleasure, according as more or less air is allowed to enter through the orifices beneath. With a very full draught the light almost vanishes, leaving only a dull blue flame of great heating power, like that of the blowpipe, corresponding to the perfect combustion of the gas without precipitation of its carbon. 4. On the other hand, too small a draught of air is equally prejudicial; not merely because a portion of the carbon thus escapes unconsumed in smoke, but also because the highest illuminating power of the flame is obtained only when the precipitated charcoal is heated to whiteness, a circumstance which requires a considerable draught of air. Hence the flame of dense oil gas, or of oil in a wick, burns with a yellow light without a chimney; but when it is increased in intensity by a chimney draught, it burns with a brilliant white flame.

From the consideration of the preceding facts, it is possible to give to coal gas its highest illuminating power. The burners are either simple beaks perforated with a small round hole, or circles with a series of holes to form an argand flame, as shown in fig. 497, or two holes drilled obliquely, to make the flame cross, like a swallow’s tail, or with a slit constituting the sheet of flame called a bat’s wing, like most of the lamps in the streets of London. These burners are mounted with a stop-cock for regulating the quantity of gas.

The height of the flame, which with like pressure depends upon the size of the orifice, and with like orifice upon the amount of pressure, the latter being modified by the stop-cock, is for simple jets in the open air, as follows:--

Length of the flame 2 3 4 5 6 inches Intensity of the light 55·6 100 150 197·8 247·4 Volume of gas consumed 60·5 101·4 126·3 143·7 182·2 Light with equal consumption 100 109 131 150 150

When the length exceeds five inches, nothing is gained in respect to light. For oil gas the same statements will serve, only on account of its superior richness in carbon, it does not bear so long a flame without smoke. Thus:--

Length of the flame 1 2 3 4 5 inches Intensity of the light 22 63·7 96·5 141 178 Gas consumed 33·1 78·5 90 118 153 Light with equal consumption 100 122 159 181 174

The diameter of the orifice for single jets, or for several jets from the same beak, is one twenty-eighth of an inch for coal gas, and one forty-fifth for oil gas.

When several jets issue from the same burner, the light is improved by making all the flames unite into one. In this case the heat becomes greater, for the combined flame presents a smaller surface to be cooled, than the sum of the smaller flames. The advantage gained in this way, may be in the ratio of 3 to 2, or 50 per cent. In an argand burner, the distances of the orifices for coal gas should be from 16/100 to 18/100 of an inch, and for oil gas 12/100. If the argand ring has ten orifices, the diameter of the central opening should be = 4/10 of an inch; if 25 orifices, it should be one inch for coal gas; but for oil gas with 10 orifices, the central opening should have a diameter of half an inch, and for 20 orifices, one inch. The pin holes should be of equal size, otherwise the larger ones will cause smoke, as in an argand flame with an uneven wick. The glass chimney is not necessary to promote the combustion of an argand coal gas flame, but only to prevent it from flickering with the wind, and therefore it should be made so wide as to exercise little or no influence upon the draught. A narrow chimney is necessary merely to prevent smoke, when a very strong light, with a profusion of gas is desired. Oil gas burned in an argand beak requires a draught chimney, like a common argand lamp, on account of the large quantity of carbon to be consumed. The most suitable mode of regulating the degree of draught can be determined only by experiment, and the best construction hitherto ascertained is that represented in fig. 498. Fig. 499. exhibits the view from above, of the rim or ring c, upon which the chimney b stands, and which surrounds the perforated beak. The ring is made of open fretwork, to permit the free passage of air upwards to strike the outside of the flame. The thin annular disc d, which is laid over its fellow disc c, in the bottom of the chimney-holder, being turned a little one way or other, will allow more or less air to pass through for promoting more or less, the draught or ventilation. The draught in the central tube of the burner may be regulated by the small disc e, whose diameter is somewhat smaller than that of the ring of the burner, and which by turning the milled head f, of the screw, may be adjusted with the greatest nicety, so as to admit a greater or smaller body of air into the centre of the cylindrical flame.

In mounting gas-lights, and in estimating beforehand their illuminating effects, we must keep in mind the optical proposition, that the quantity of light is inversely as the square of the distance from the luminous body, and we must distribute the burners accordingly. When for example a gas-light placed at a distance of ten feet, is required for reading or writing to afford the same light as a candle placed at a distance of two feet; squaring each distance, we have 100 and 4; therefore 100/4 = 25, shows us that 25 such lights will be necessary at the distance of 10 feet.

Concerning portable gas-light, with the means of condensing it, and carrying it from the gas works to the places where it is to be consumed, we need say nothing, as by the improvements lately made in the purification and distribution of coal-gas, the former system has been superseded.

It is well known that light gas deteriorates very considerably by keeping, especially when exposed to water over an extensive surface; but even to a certain degree over oil, or in close vessels. An oil-gas which when newly prepared has the specific gravity of 1·054, will give the light of a candle for an hour, by consuming 200 cubic inches; will, after two days, give the same light by consuming 215 cubic inches per hour; and after four days, by consuming 240 cubic inches in the like time. With coal-gas the deterioration appears to be more rapid. When newly prepared, if it affords the light of a candle with a consumption of 400 cubic inches per hour; it will not give the same light after being kept two days, except with a consumption of 430 inches; and after four days, of 460. Oil-gas three weeks old has become so much impaired in quality that 600 inches of it were required per hour to furnish the light of a candle. All light gas should be used therefore as soon as possible after it is properly purified.

Economical considerations.--The cost of gas-light depends upon so many local circumstances, that no estimate of it can be made of general application; only a few leading points may be stated. The coals required for heating the retorts used to constitute one half of the quantity required for charging the retorts themselves. When five retorts are heated by one fire, the expenditure for fuel is only one third of that when each retort has a fire. The coak which remains in the retorts constitutes about 60 per cent. of the weight of the original coal; but the volume is increased by the coaking in the proportion of 100 to 75. When the coak is used for heating the retorts, about one half of the whole is required. If we estimate the coak by its comparative heating power, it represents 65 per cent. of the coals consumed. One hundred pounds of good coal yield in distillation 10 pounds of ammoniacal liquor, from which sulphate or muriate of ammonia may be made, by saturation with sulphuric or muriatic acid, and evaporation. The liquor contains likewise some cyanide of ammonia, which may be converted into prussian blue by the addition of sulphate of iron, after saturation with muriatic acid.

Two hundred pounds of coal afford about 17 pounds of tar. This contains in 100 pounds 26 pounds of coal oil, and 48 pounds of pitch. The tar is sometimes employed as a paint to preserve wood and walls from the influence of moisture, but its disagreeable smell limits its use. The coal oil when rectified by distillation, is extensively employed for dissolving caoutchouc in making the varnish of waterproof cloth, and also for burning in a peculiar kind of lamps under the name of naphtha. Oil of turpentine however is often sold and used for this purpose, by the same name. If the coal oil be mixed with its volume of water, and the mixture be made to boil in a kettle, the mingled vapours when passed through a perforated nozzle may be kindled, and employed as a powerful means of artificial heat. The water is not decomposed, but it serves by its vapour to expand the bulk of the volatile oil, and to make it thereby come into contact with a larger volume of atmospherical air, so as to burn without smoke, under a boiler or any other vessel. The pitch may be decomposed into a light-gas.

The relative cost of light from coal gas and oil gas may be estimated as one to six, at least. Rosin gas is cheaper than oil gas. See ROSIN.

I shall conclude this article with a summary of the comparative expense of different modes of illumination, and some statistical tables.

One pound of tallow will last 40 hours in six mould candles burned in succession, and costs 8_d._; a gallon of oil, capable of affording the light of 15 candles, for 40 hours costs 5_s._, being therefore 1/2 of the price of mould candles, and 6/15 of the price of dips. The cost of wax is about 3-1/2 times that of tallow; and coal gas, as sold at the rate of 9_s._ for 1000 cubic feet, will be one sixth the price of mould candles; for 500 cubic inches of coal gas give a light equal to the above candle for an hour; therefore 40 × 500 = 20,000 cubic inches = 11·57 cubic feet, worth 1-1/4_d._, which multiplied by 6 gives 7-1/2_d._ the average price of mould candles per pound.

The author of the article Gas-light in the Encyclopædia Britannica, observes, in reference to the economy of this mode of illumination, that while the price of coal, in consequence of the abundant and regular supply of that article, is liable to little fluctuation, the cost of wax, tallow, and oil, on account of the more precarious nature of the sources from which they are obtained, varies exceedingly in different seasons. “Assuming that a pound of tallow candles, which last when burned in succession forty hours, costs nine-pence,” (seven-pence halfpenny is the average price), “that a gallon of oil, yielding the light of 600 candles for an hour, costs two shillings,” (five shillings is the lowest price of a gallon of such oil as a gentleman would choose to burn in his lamp), “that the expense of the light from wax is three times as great as from tallow, and that a thousand cubic feet of coal gas cost nine shillings;” he concludes the relative cost to be for the same quantity of light,--from wax, 100; tallow, 25; oil, 5; and coal-gas, 3. I conceive the estimate given above to be much nearer the truth; when referred to wax called 100, it becomes, for tallow, 28·6; oil, 14·3; coal gas, 4·76.

Gas-lighting has received a marvellous development in London. In the year 1834, the number of gas lamps in this city was 168,000, which consumed daily about 4,200,000 cubic feet of gas. For the purpose of generating this gas, more than 200,000 chaldrons, or 10,800,000 cubic feet of coals were required.

For the following valuable statistical details upon gas-light, my readers are indebted to Joseph Hedley, Esq., engineer, of the Alliance Gas Works, Dublin; a gentleman who to a sound knowledge of chemistry, joins such mechanical talent and indefatigable diligence, as qualify him to conduct with success, any great undertaking committed to his care. He has long endeavoured to induce the directors of the London gas-works to employ a better coal, and generate a more richly carburetted gas, which in much smaller quantity would give as brilliant a light, without heating the apartments unpleasantly, as their highly hydrogenated gas now does. Were his judicious views adopted, coal gas would soon supersede oil, and even wax candles, for illuminating private mansions.

Copy of a paper laid before a Committee of the House of Commons, showing not only the relative values of the Gases produced at the undermentioned places, but showing in like manner the relative economy of Gas as produced at the different places, over candles. By Joseph Hedley, Esq.

+---------------+---------------------------------------------------+ |Names of the |Illuminating power of a single Jet of Gas-flame | |Places where |four inches high, taken by a comparison of Shadows.| |Experiments | +-----------------------------------------+ |were made. | |The Jet of Gas burnt, four inches high, | | | |consumed per hour and was equal to the | | | |Candles in the last column. | | | | +----------------------------------+ | | | |Gas required to be equal to 100 | | | | |lbs. of mould Candles, 6 to the | | | | |lb., 9 inches long each.[A] | | | | | +---------------------------+ | | | | |Selling price of Gas per | | | | | |meter per 1000 cubic feet. | +---------------+---------+------+------+-------+-------------------+ | |_Equal to|_Cubic|_Cubic| | | |Candles.|Feet.|Feet._|s. d.| |Birmingham; }| | | | | |Birmingham and}| | | | | |Staffordshire;}| 2·572 | 1·22 | 2704 |10 0 | |two Companies }| | | | | |Stockport | 3·254 | ·85 | 1489 |10 0 | |Manchester | 3·060 | ·825| 1536 | 8 0 | |Liverpool Old}| | | | | |Company[C] }| 2·369 | 1·1 | 2646 |10 0 | |Liverpool New} | | | | | |Gas Company } | 4·408 | ·9 | 1164 |10 0 | |Bradford | 2·190 | 1·2 | 3123 | 9 0 | |Leeds | 2·970 | ·855| 1644 | 8 0 | |Sheffield | 2·434 | 1·04 | 2440 | 8 0 | |Leicester | 2·435 | 1·1 | 2575 | 7 6 | |Nottingham | 1·645 | 1·3 | 4200 | 9 0 | |Derby | 1·937 | 1·2 | 3521 |10 0 | |Preston | 2·136 | 1·15 | 3069 |10 0 | | | | | | | |London | 2·083 | 1·13 | 3092 |10 0 | +---------------+---------+------+------+-------+

+---------------+---------------------------------------------------+ |Names of the |Cost of Gas equal in illuminating power to 100 lbs.| |Places where |of candles.[B] | |Experiments | +----------------------------------------+ |were made. | |Average discount allowed off the charge | | | |for Gas. | | | | +-------------------------------+ | | | |Net cost of Gas equal to 100 | | | | |lbs. of Candles. | | | | | +--------------------+ | | | | |Specific gravity of | | | | | |the Gas. | +---------------+----------+--------+----------+----+---------------+ | | | Per | | | | |L. s. d.|Cent. |L. s. d.| | |Birmingham; }| | | | | |Birmingham and}| | | | | |Staffordshire;}| 1 7 0 | 9 | 1 4 7 |·541| |two Companies }| | | | | |Stockport | 0 14 11 | 12-1/2 | 0 13 0 |·539| |Manchester | 0 12 3 | 11-1/4 | 0 0 10 |·534| |Liverpool Old}| | | | | |Company[C] }| 1 6 5 | 6-1/4 | 1 4 9 |·462| |Liverpool New} | | | | | |Gas Company } | 0 11 8 | 6-1/4 | 0 9 10 |·580| |Bradford | 1 8 1 | 12-1/2 | 1 4 6 |·420| |Leeds | 0 13 2 | 6-1/4 | 0 12 4 |·530| |Sheffield | 0 19 6 | 6-1/4 | 0 18 3 |·466| |Leicester | 0 19 3 | 15 | 0 16 5 |·528| |Nottingham | 1 17 9 | 15 | 1 11 3 |·424| |Derby | 1 15 4 | 15 | 1 10 0 |·448| |Preston | 1 10 8 | 15 | 1 6 2 |·419| | | | none | | | |London | 1 10 11 |allowed.| 1 10 11 |·412| +---------------+----------+--------+----------+----+ [A] 100 lbs. of candles are estimated to burn 5700 hours. [B] The candles cost 3_l._ 2_s._ 6_d._ [C] The Liverpool Old Company have since resorted to the use of Cannel coal, and consequently very nearly assimilate to the Liverpool New Company in illuminating power.

MEMORANDUM.--It will not fail to be observed that in deducing the comparative value between candles and gas by these experiments, the single jet (and in every instance, of course, it was the same), has been the medium. This however, though decidedly the most correct way of making the comparative estimate of the illuminating power of the several gases, is highly disadvantageous in the economical comparison, inasmuch as gas burnt in a properly regulated argand burner, with its proper sized glass, air aperture, and sufficient number of holes, gives an advantage in favour of gas consumed in an argand, over a jet burner, of from 30 to 40 per cent. At the same time it must not be overlooked that in many situations where great light is not required, it will be found far more economical to adopt the use of single jets, which by means of swing brackets and light elegant shades, becomes splendid substitutes for candles, in banking establishments, offices, libraries, &c. &c.

NOTE.--In Glasgow, Edinburgh, Dundee, Perth, and the Scotch towns generally the Parrot or Scotch Cannel coal is used; in illuminating power and specific gravity the gas produced is equal to that from the best description of Cannel coal in England. The price per 1000 cubic feet ranges about 9_s._, with from 5 to 30 per cent. off for discounts, leaving the net price about 9_s._ to be equal in the above table to 100 lbs. of candles.

Epitome of Experiments made in Gas produced from different qualities of Coal, and consumed in different kinds of Burners:

Tried at the Sheffield Gas Light Company’s Works, and laid before a Committee of the House of Commons. By Joseph Hedley, Esq.

+------+-----------+----------+--------+---------+--------+-------+ | | | | | | | | | Date |Description|Species of|Specific|Distance |Gas | | | 1835.|of Burner. |Coal. |Gravity |of Candle|consumed|Height | | | | |of Gas. | from |per |of Gas | | | | | | Shadow. |Hour. |Flame. | | | | | | | | | | | | | | | | | +------+-----------+----------+--------+---------+--------+-------+ | | | | | |Cubic | In- | |May.| | | |Inches.|Feet. |ches.| | 8 | Single Jet|Deep Pit | ·410 | 75 | 1· |4 | | 9 | Ditto |Mortormley| ·450 | 74 | ·95 |4 | | 9 | Ditto |Cannel | ·660 | 61-1/4 | ·7 |4 | | 8 |{ Argand }| | | | | | | |{ 14 holes}|Deep Pit | ·410 | 34 | 3·3 |3-1/2 | | 9 | Ditto |Mortormley| ·450 | 33 | 3·1 |3-1/2 | | 9 | Ditto |Cannel | ·660 | 29 | 2·6 |3-1/3 | +------+-----------+----------+--------+---------+--------+-------+

+------+-------------+-----------+------------+----------+ | |Equal to | | |Cost of | | Date |Mould Tallow |Gas equal |Cost of Gas |100 lbs. | | 1835.|Candles, 6 |to 100 lbs.|at 8_s._ |of Mould | | |to the pound,|of Mould |per 1000 |Candles | | |9 inches | Candles. |cubic feet. |at 7_s._ | | |long each. | | |6_d._ per | | | | | |dozen lbs.| +------+-------------+-----------+------------+----------+ | | | Cubic | | | |May.| Candles. | Feet. |L. s. d. |L. s. d.| | 8 | 2·36 | 2415 | 0 19 3-1/2}| | | 9 | 2·434 | 2224 | 0 17 9-1/2}| | | 9 | 3·54 | 1127 | 0 9 0 }| | | 8 | | | }| 3 2 6 | | | 11·53 | 1631 | 0 13 0-1/2}| | | 9 | 12·24 | 1443 | 0 11 6-1/2}| | | 9 | 15·85 | 935 | 0 7 5-3/4}| | +------+-------------+-----------+------------+----------+

Copy of Experiments made at the Alliance Gas Company’s Works in Dublin, during the past year 1837. By Joseph Hedley, Esq.

Results of experiments on the qualities of various coals for the production of gas; its value in illuminating power; produce of coke, and quality; and other particulars important in gas-making:--

1st Experiment, Saturday, May 27th, 1837.--Deane coal, (Cumberland). 2 cwt. of 112 lbs. each (or 224 lbs.) produced 970 cubic feet of gas; 4 bushels of coke of middling quality; specific gravity of the gas, 475. Consumed in a single-jet burner, flame 4 inches high, 1-4/10ths cubic feet per hour; distance from shadow 76 inches or 2·3 mould candles. Average quantity of gas made from the charge (6 hours) 4·33 cubic feet per lb., or 9,700 cubic feet per ton of 20 cwt. Increase of coke over coal in measure, not quite 30 per cent. Loss in weight between coal, coke and breize 56 lbs., converted into gas, tar, ammonia, &c.

2nd Experiment, May 28th.--Carlisle coal, (Blenkinsopp). 224 lbs. produced 1010 cubic feet of gas, 4 bushels of coke of good quality though small; increase of coke over coal in measure not quite 30 per cent. Loss in weight, same as foregoing experiment. Average quantity of gas made from the charge (6 hours) 4·5 cubic feet per lb. or 10,080 per ton.

Illuminating power of the Gas.

+-------------------------------+---------+--------+--------+--------+ | |Consumed |Distance|Equal to|Specific| | |per hour,|from |candles.|gravity.| | |single |candle. | | | | |jet. | | | | +-------------------------------+---------+--------+--------+--------+ | | feet. | in- | | | | | |ches. | | | |At the end of the 1st hour | 1-1/10 | 70 | 2·72 | ·475 | |Ditto ditto with 20-hole}| | | | | |argand burner }| 5 | 25 | 21·33 | ·475 | |When charge nearly off | 1-4/10 | 85 | 1·84 | ·442 | |When charge quite off, with }| | | | | |20-hole argand burner }| 9 | 100 | not 1 | ·256 | +-------------------------------+---------+--------+--------+--------+

3rd Experiment, May 29th.--Carlisle coal (Blenkinsopp). 112 lbs. produced 556 cubic feet of gas. Other products, loss of weight, &c., same proportion as foregoing experiment. Average quantity of gas made from the charge (6 hours) 4·96 cubic feet per lb., or 11,120 per ton.

In this experiment the quantity of gas generated every hour was ascertained; the illuminating power, the specific gravity, and the quantity of gas consumed by the single jet with a flame 4 inches high, was tried at the end of each hour, with the respective gases generated at each hour; and the following is a table of results.

RESULTS.

+-----+-------------+---------------+--------+---------+------------+ | | | Consumed |Specific|Distance |Illuminating| |Hour.|Gas produced.| per hour |gravity.|of candle|power equal | | | |per single jet,| |from | to mould | | | | 4 inches high.| |shadow. | candles. | +-----+-------------+---------------+--------+---------+------------+ | |cubic feet.| cubic feet. | | in- | | | | | | | ches. | | | | { | 11-1/2-10ths.}| | | | |1st. | 150 { | or 1·15 }| ·534 | 70 | 2·72 | | | | | | | | |2nd. | 120 | 11 | ·495 | 75 | 2·36 | |3rd. | 95 | 12 | ·344 | 75 | 2·36 | |4th. | 95 | 15 | ·311 | 80 | 2·08 | |5th. | 80 | 17 | ·270 | 85 | 1·81 | |6th. | 16 | 29 | ·200 | 100 | not one | | +-------------+---------------+ | | |Total| 556 | or 92-1/3 or 2 feet 9 inches. | | +-----+-------------+----------------------------------+------------+

Average of the above gas, 6-hour charge. 92-1/3 16-10ths. ·359 81 2·03 nearly

Average of the above gas at 4-hour charge. 115 12-1/3-10ths. ·421 75 2·36

Production of gas in 6 hours 556 feet, or at the rate of 11,120 cubic feet per ton. Ditto in 4 hours 460 feet, or at the rate of 9,200 ditto.

The relative value of these productions of gas is as follows, viz.:

11,120 at 16-10ths per hour nearly, (or 1·5916 accurately) and equal to 203 candles; the 11,120 feet would be equal to and last as long as 1597 candles, or 266-1/6 lbs. of candles.

9200 at 12-1/3-10ths. per hour, (or 1·2375 accurately,) and equal to 236 candles; the 9200 feet would be equal to 1949 candles, or 324-5/6 lbs. candles.

Now 266-1/6 lbs. of mould candles, at 7_s._ 6_d._ per dozen lbs. will cost 8_l._ 6_s._ 4-1/2_d._, whilst

324-5/6 lbs. of do. do. at 7_s._ 6_d._ per do. do. 10_l._ 3_s._

Shewing the value of 4-hour charges, over 6-hour charges; and of 9,200 cubic feet over 11,120 cubic feet.

Note.--9500 cubic feet of Wigan cannel coal gas are equal in illuminating power to 859 1-6th lbs. of candles, which at 7_s._ 6_d._ per dozen lbs. will cost 25_l._ 10_s._ 5-1/2_d._ It is also found that any burner with superior gas, will consume only about half the quantity it would do with common gas.

4th Experiment, May 30th.--Cannel and Cardiff coal mixed 1/2 and 1/2, together 112 lbs., produced 460 feet of gas; 2 bushels of coke of good quality; increase of coke over coal in measure about 30 per cent.; loss in weight, 41 lbs.; coke weighed 71 lbs., no breize. Average quantity of gas made from the charge, (4 hours) 4·1 cubic feet, per lb., or 9·200, per ton.

Illuminating power.--At end of first hour.

Candles. Cubic feet. Distance of candle} {Consumed per hour, single} from shadow } 73 or 2·49 {jet, 4 inches high } 12-10ths

At end of 2nd hour, 70 or 2·72 Do. do. do. 11-1/2-10ths do.

At end of 3d hour. This gas very indifferent.

Average of the three 70 or 2·72 Do. do. do. 11-1/2-10ths

Specific gravity 3·44; 5 feet per hour, with a 20-hole argand burner, equal to 14·66 candles.

5th Experiment, May 31st.--Carlisle coal, 112 lbs. produced 410 feet of gas; other products, same as in former experiments with this coal, but heat very low.

Illuminating power and produce of gas.

{Average of this gas: specific gravi- {1st hour 120 cubic feet {ty, 540; distance of candle from {2nd 100 {shadow, 55 inches, or 4·4 candles 410 ft {3d 90 {consumed per single jet, 9-10ths of a {4th 100 {cubic foot per hour. 20-hole argand {burner, 4 feet per hour, equal to {21·33 candles.

It is possible, from the superior quality of this gas, that a little of the cannel gas made for a particular purpose, may have have got intermixed with it in the experimental gasholder and apparatus.

A variety of other experiments were tried on different qualities of coal, and mixtures of ditto, too tedious to insert here, though extremely valuable, and all tending to shew the superior value of gas produced at short over long charges; and also showing the importance and value of coal producing gas of the highest illuminating power; among which the cannel coal procured in Lancashire, Yorkshire, and some other counties of England and Wales, and the Parrot or splent coal of Scotland, stand pre-eminent.

Note.--In all the foregoing experiments the same single-jet burner was used; its flame in all instances exactly 4 inches high.

The coal when drawn from the retort was slaked with water, and after allowing some short time for drying, was weighed.

A TABLE of the number of hours Gas is burnt in each month, quarter and year.

+---------------+-----+----+----+----+----+----+----+----+----+----+ |Time of |July.|Aug.|Sep.|Oct.|Nov.|Dec.|Jan.|Feb.|Mar.|Apl.| |Burning. | | | | | | | | | | | | | | | | | | | | | | | +---------------+-----+----+----+----+----+----+----+----+----+----+ | o’clock.| | | | | | | | | | | |From Dusk to 6| -- | --| 2| 31| 62| 80| 65| 33| 4| --| | -- 7| -- | 14| 22| 62| 92| 111| 96| 61| 31| 4| | -- 8| -- | 40| 52| 93| 122| 142| 127| 89| 62| 28| | -- 9| 13 | 71| 82| 124| 152| 173| 158| 117| 93| 58| | -- 10| 44 | 102| 112| 155| 182| 204| 189| 145| 124| 88| | -- 11| 75 | 133| 142| 186| 212| 235| 220| 173| 155| 118| | -- 12| 106 | 164| 172| 217| 242| 266| 251| 201| 186| 148| |All night -| 217 | 307| 345| 421| 473| 527| 512| 411| 382| 295| |Morning from 4| -- | 16| 48| 80| 110| 137| 137| 98| 71| 28| | -- 5| -- | --| 18| 49| 80| 106| 106| 70| 40| 3| | -- 6| -- | --| --| 18| 50| 75| 75| 42| 9| --| | -- 7| -- | --| --| --| 20| 44| 44| 14| --| --| +---------------+-----+----+----+----+----+----+----+----+----+----+

+---------------+----+-----++-----+-----+-----+-----+-----+----+ |Time of |May.|June.||Mid. |Mic. |Xms. |Lady |Totl.| | |Burning. | | ||quar.|quar.|quar.|day | of | | | | | || | | |quar.|Year.| | +---------------+----+-----++-----+-----+-----+-----+-----+----+ | o’clock.| | || | | | | | | |From Dusk to 6| --| -- || -- | 2 | 173 | 102 | 277 |} | | -- 7| --| -- || 4 | 36 | 265 | 188 | 493 |} | | -- 8| 4| -- || 32 | 92 | 357 | 278 | 759 |} | | -- 9| 29| 8 || 95 | 166 | 449 | 368 |1078 |} | | -- 10| 60| 38 || 186 | 258 | 541 | 458 |1443 |} | | -- 11| 91| 68 || 277 | 350 | 633 | 548 |1808 |}[A]| | -- 12| 122| 98 || 368 | 442 | 725 | 638 |2173 |} | |All night -| 242| 195 || 732 | 869 |1421 |1305 |4327 |} | |Morning from 4| 2| -- || 30 | 64 | 327 | 306 | 727 |} | | -- 5| --| -- || 3 | 18 | 235 | 216 | 472 |} | | -- 6| --| -- || -- | -- | 143 | 126 | 269 |} | | -- 7| --| -- || -- | -- | 64 | 58 | 122 |} | +---------------+----+-----++-----+-----+-----+-----+-----+----+ [A] For Sundays off, deduct one seventh.

Copy of a Paper submitted to a Committee of the House of Commons in the Session of 1837, being a Synopsis of the proceedings of the undermentioned principal Gas-Light Establishments of England; and procured by actual Survey and Experiments between the Years 1834 and 1837. By Joseph Hedley, Esq.

+--------------+------------------------------+------------------+--------+ |Name of the |Price of Gas per Meter, and |Price of Coal, and|Average | |Place where |Discounts allowed. |Description; de- |Quantity| |Gas Works | |livered per Ton. |of Gas | |are situated. | | |made per| | | | |Ton of | | | | |Coals. | +--------------+------------------------------+------------------+--------+ | | | |Cu. | | | | |ft. | +--------------+------------------------------+------------------+--------+ |Birmingham Gas|10_s._ per meter cub. feet. |Lump coal from |6,500 | |Company. | Discounts |West Bromwich pits| | | | per an. per cent. |risen much of | | | | 10_l._ to 30_l._ 2-1/2 |late. 1837, 11_s._| | | | 30_l._ to 50_l._ 5 |10_d._ | | | | 50_l._ to 75_l._ 7-1/2 | | | | | 75_l._ to 100_l._ 10 | | | | |100_l._ & upwards 15 | | | +--------------+------------------------------+------------------+--------+ |Birmingham and|10_s._ per meter cub. feet. |From West Bromwich|6,500 | |Staffordshire.|Discounts as above. |pits, 1837, 9_s._ | | | | |3_d._ | | +--------------+------------------------------+------------------+--------+ |Macclesfield. |10_s._ per meter cub. feet. |Common, 8_s._ |6,720 | | | Discounts |average 1831 | | | |Above and not per cent. | | | | | exceeding | | | | | 50_l._ 75_l._ 5 | | | | | 75_l._ 100_l._ 7-1/2 | | | | |100_l._ 125_l._ 10 | | | | |125_l._ 150_l._ 12-1/2 | | | | |150_l._ 175_l._ 15 | | | | |175_l._ 200_l._ 17-1/2 | | | | |200_l._ & upwards 20. | | | +--------------+------------------------------+------------------+--------+ |Stockport. |10_s._ per meter cub. feet. |Coal 10_s._ 6_d._ |7,800 | | |Discounts same as Maccles- |cannel 19_s._ | | | |field. Macclesfield discounts |6_d._ about half | | | |taken from Stockport card. |and half used. | | | | |Average 15_s._ | | | | |1834. | | +--------------+------------------------------+------------------+--------+ |Manchester. |10_s._ per m. cub. ft. 1834. |15_s._ 2_d._ |9,500 | | | 9_s._ and 8_s._ -- 1837. |average. | | | | Discounts |Oldham } | | | | and under per cent.|Watergate }cannel.| | | | 50_l._ 100_l._ 2-1/2 |Wigan } | | | |100_l._ 150_l._ 5 |Mixed, 1834. | | | |150_l._ 200_l._ 7-1/2 | | | | |200_l._ 225_l._ 10 | | | | |225_l._ 250_l._ 12-1/2 | | | | |250_l._ 300_l._ 15 | | | | |300_l._ 400_l._ 17-1/2 | | | | |400_l._ and upwards 20 | | | +--------------+------------------------------+------------------+--------+ |Liverpool Old |10_s._ per meter cub. feet. |7_s._ 3_d._ per |8,200 | |Company, 1834.| Discounts per ct.|ton of 112 lbs. | | | | 10_l._ & under 50_l._ 2-1/2|per cwt. Ormskirk | | | | 50_l._ to 100_l._ 5 |or Wigan slack. | | | |100_l._ to 200_l._ 7-1/2| | | | |300_l._ & upwards 10 | | | +--------------+------------------------------+------------------+--------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel coal | | |similar to the Liverpool New Gas and Coal Company, pro- | | |ducing nearly similar results, which see. | +--------------+------------------------------+------------------+--------+ |Liverpool New |10_s._ per meter cub. feet. |18_s._ all cannel |9,500 | |Gas and Coke, |Discounts same as Liverpool |Wigan. | | |1835. |Old Company. | | | +--------------+------------------------------+------------------+--------+ |Bradford, |9_s._ per meter cubic feet to |8_s._ 6_d._ per |8,000 | |1834. |large consumers. |ton. 3 sorts used | | | | Discounts per cent. |average. Slack | | | | 20_l._ to 30_l._ 5 |5_s._ 6_d._ Low | | | | 30_l._ to 40_l._ 7-1/2 |moor 8_s._ 10_d._ | | | | 40_l._ to 60_l._ 10 |Catherine slack | | | | 60_l._ to 80_l._ 12-1/2 |8_s._ | | | | 80_l._ to 100_l._ 15 | | | | |100_l._ & upwards 20 | | | | |Small consumers, 10_s._ per | | | | |meter cub. feet, and 5 per | | | | |cent. off from 10_l._ to | | | | |20_l._ | | | +--------------+------------------------------+------------------+--------+ |Leeds, 1834. |8_s._ per meter cubic feet. |8_s._ per ton av- |6,500 | | | Discounts |erage. 2-3ds com- | | | | 2-1/2}per cent.{ 15_l._ |mon 7_s._ 1-3d | | | | 5 }on half- { 30_l._ |cannel, 10_s._ | | | | 7-1/2}yearly { 50_l._ | | | | |10 }payments { 100_l._ | | | +--------------+------------------------------+------------------+--------+ |Sheffield, |8_s._ per meter cubic feet. |7_s._ 9_d._ per |8,000 | |1835. |Discounts same as Leeds. |ton average. 3 | | | | |sorts used 1, | | | | |2-10ths. cannel, | | | | |at 16_s._ 8, | | | | |2-10ths. deep pit,| | | | |7_s._ 1-10th silk | | | | |stone, 10_s._ | | +--------------+------------------------------+------------------+--------+ |Leicester, |7_s._ 6_d._ per meter cub. ft.|13_s._ 6_d._ aver-|7,500 | |1837. |Discounts on half-yearly |age. Derbyshire | | | |rental not exceeding 10_l._, |soft coal. | | | |5 per cent. | | | | |Above and not per cent. | | | | | exceeding | | | | |10_l._ 20_l._ 7-1/2 | | | | |20_l._ 30_l._ 10 | | | | |30_l._ 40_l._ 12-1/2 | | | | |40_l._ 50_l._ 15 | | | | |50_l._ 60_l._ 20 | | | | |60_l._ & upwards 25 | | | +--------------+------------------------------+------------------+--------+ |Derby, 1834. |10_s._ per meter cub. feet. |Same coal used as |7,000 | | |Discounts 5 to 35 per cent. |at Leicester. | | +--------------+------------------------------+------------------+--------+ |Nottingham, |9_s._ per meter cubic feet. |Ditto. |7,000 | |1834. |Discounts as above. | | | +--------------+------------------------------+------------------+--------+ |London, 1834. |10_s._ per meter cub. feet. No|17_s._ average. |8,500 | | |discounts. |Newcastle. | | +--------------+------------------------------+------------------+--------+ |Ditto, 1837. |Ditto. |Ditto. |8,500 | +--------------+------------------------------+------------------+--------+

+--------------+-----------+-------------+---------+--------+-------------+ |Name of the |Coke made |Selling Price|Material |Quantity|No. of Public| |Place where |from a Ton |of Coke. |used to |used per|or Street | |Gas Works |of Coal. | |heat Re- |Ton of |Lamps | |are situated. | | |torts. |Coal. |supplied. | +--------------+-----------+-------------+---------+--------+-------------+ |Birmingham Gas|32 bushels.|2_s._ 1_d._ |Slack. |About 5 | 490 | |Company. | |per quarter | |cwt. of | | | | |delivered, or| |slack, | | | | |about 3_d._ | |at 6_s._| | | | |per bushel. | |per ton,| | | | | | |25 per | | | | | | |cent. | | +--------------+-----------+-------------+---------+--------+-------------+ |Birmingham and|24 bush. |2_s._ 10_d._ |Slack and|5 cwt. |1,500 | |Staffordshire.|but larger |per sack of 8|Tar. |of | | | |measure |bushels. | |slack, | | | |than Bir- | | |at 4_s._| | | |mingham. | | |25 per | | | | | | |cent. | | +--------------+-----------+-------------+---------+--------+-------------+ |Macclesfield. |12 cwt. |10_s._ per |Coke. |No ac- | 220 | | | |ton. | |count | | | | | | |kept. | | +--------------+-----------+-------------+---------+--------+-------------+ |Stockport. |7 cwt. |6_s._ 8_d._ |Coal, |Ditto. | 230 | | | |per ton. |coke, and| | | | | | |tar. | | | +--------------+-----------+-------------+---------+--------+-------------+ |Manchester. |14 cwt. |Ditto. |Coke. |4, 2-3ds|2,375 | | | | | |cwt. | | +--------------+-----------+-------------+---------+--------+-------------+ |Liverpool Old |11-3/4 cwt.|8_s._ 4_d._ |Slack |6-1/2 |1,700 30 | |Company, 1834.| |per ton of |7_s._ |cwt. | | | | |112 lb. per |3_d._ | | | | | |cwt. |per ton. | | | +--------------+-----------+-------------+---------+--------+-------------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel coal | | |similar to the Liverpool New Gas and Coal Company, pro- | | |ducing nearly similar results, which see. | +--------------+-----------+-------------+---------+--------+-------------+ |Liverpool New |13 cwt. |7_s._ 6_d._ |Coke and |5-1/2 |Only a few. | |Gas and Coke, | |per ton. |slack. |cwt. | | |1835. | | | | | | +--------------+-----------+-------------+---------+--------+-------------+ |Bradford, |13 cwt. |12_s._ per |Coke. |8-1/2 |220 | |1834. | |ton. | |cwt. | | +--------------+-----------+-------------+---------+--------+-------------+ |Leeds, 1834. |12 cwt. |7_s._ 6_d._ |Ditto. |5-1/4 |517 | | | |per ton. | |cwt. | | +--------------+-----------+-------------+---------+--------+-------------+ |Sheffield, |10 cwt. of |10_s._ per |Ditto. |3-1/2 |600 | |1835. |saleable |ton. | |cwt. | | | |coke. | | | | | +--------------+-----------+-------------+---------+--------+-------------+ |Leicester, |4 quarters.|10_s._ 8_d._ |Coke |About |414 | |1837. | |or 2_s._ |tar, &c. |1-3d of | | | | |8_d._ per qr.| |coke. | | +--------------+-----------+-------------+---------+--------+-------------+ |Derby, 1834. |Ditto. |Ditto. |Coke. |Ditto. |219 | +--------------+-----------+-------------+---------+--------+-------------+ |Nottingham, |Ditto. |Ditto. |Ditto. |Ditto. |300 | |1834. | | | | | | +--------------+-----------+-------------+---------+--------+-------------+ |London, 1834. |36 bush. |12_s._ per |Ditto. |13 bush.|26,280 | +--------------+-----------+-------------+---------+--------+-------------+ |Ditto, 1837. |Ditto. |Ditto. |Ditto. |Ditto. |30,400 | +--------------+-----------+-------------+---------+--------+-------------+

+--------------+------------+----------+--------------+-------------------+ |Name of the |Description.|Price paid|Who lights, |No. of Hours, or | |Place where |---- |per Annum |cleans, puts |Time burnt in the | |Gas Works |Size or |for Ditto.|out, and re- |Year. | |are situated. |Sort. | |pairs. | | +--------------+------------+----------+--------------+-------------------+ | | |L. s. d.| | | +--------------+------------+----------+--------------+-------------------+ |Birmingham Gas|Batswings, | |Company, and |226 nights, or 2938| |Company. |460 | 1 10 0 |provides |hours, 9 months, | | |30 | 2 0 0 |posts, ser- |omitting 5 nights | | | | |vices, &c. |for moons. | +--------------+------------+----------+--------------+-------------------+ |Birmingham and|Batswings. |average |Ditto. |234 nights, or 3042| |Staffordshire.| | 1 18 0 | |hours. | +--------------+------------+----------+--------------+-------------------+ |Macclesfield. |Ditto. | 2 10 0 |Company. |8 months, omitting | | | | | |5 nights for moons.| +--------------+------------+----------+--------------+-------------------+ |Stockport. |Ditto. | 2 10 0 |Comrs. provide|8 months. 4 nights | | | | 1834. |lamps and |omitted for moons. | | | | 2 0 0 |posts. Compa- |237 nights--2800 | | | | 1837. |ny’s service |hours. | | | | |light, repair,| | | | | |clean, and ex-| | | | | |tinguish. | | +--------------+------------+----------+--------------+-------------------+ |Manchester. |Single-jets | 1 2 0 |Commissioners |3390 hours. | | |and flat | 2 0 0 |of police. | | | |flames, | | | | | |about half | | | | | |and half. | | | | +--------------+------------+----------+--------------+-------------------+ |Liverpool Old |Batswings, | 4 10 0 |Company light,|3600 hours. | |Company, 1834.|1 jet, | 2 5 0 |clean, put | | | |2 -- | 2 13 0 |out, and re- | | | |3 -- | 3 2 9 |pair. | | | |4 -- | 3 13 11 | | | +--------------+------------+----------+--------------+-------------------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel coal | | |similar to the Liverpool New Gas and Coal Company, pro- | | |ducing nearly similar results, which see. | +--------------+------------+----------+--------------+-------------------+ |Liverpool New |Argands. | 4 0 0 |Commissioners.|3000 hours. | |Gas and Coke, | | | | | |1835. | | | | | +--------------+------------+----------+--------------+-------------------+ |Bradford, |Batswings. | 2 12 6 |Company light,|8 months, omitting | |1834. | | |repair, &c. |7 nights, 2600 | | | | | |hours to 4 o’clock | | | | | |in the morning. | +--------------+------------+----------+--------------+-------------------+ |Leeds, 1834. |Ditto. | 2 12 6 |Commissioners,|2330 hours. | | | | |except extin- | | | | | |guishing, for | | | | | |which Company | | | | | |pay 3_s._ | | | | | |10_d._ per | | | | | |lamp. | | +--------------+------------+----------+--------------+-------------------+ |Sheffield, |Ditto. | 2 10 0 |Company pro- |2200 hours. | |1835. | | |vide lamps, | | | | | |clean, repair,| | | | | |put out, &c. | | +--------------+------------+----------+--------------+-------------------+ |Leicester, |Ditto. | 2 18 6 |Company light,|From August 14th to| |1837. | | |put out, and |September 1st, | | | | |clean. |omitting 3 nights | | | | | |for moons, 3000 | | | | | |hours. | +--------------+------------+----------+--------------+-------------------+ |Derby, 1834. |Ditto. | 2 2 0 |Commissioners |2173 hours, from | | | | 2 7 0 |light, put |August to May. | | | | |out, &c. | | +--------------+------------+----------+--------------+-------------------+ |Nottingham, |Ditto. | 3 3 0 |Commissioners |All the year, 4327 | |1834. | | |light, clean, |hours. | | | | |repair, &c. | | +--------------+------------+----------+----------------------------------+ |London, 1834. |Ditto. | 4 0 0 |Company light,|4327 hours, all the| | | | |clean, put |year. | | | | |out, but not | | | | | |repair. | | +--------------+------------+----------+--------------+-------------------+ |Ditto, 1837. |Ditto. | 4 0 0 |Ditto. |Ditto. | +--------------+------------+----------+--------------+-------------------+

+--------------+------------+---------+----------+------------------------+ |Name of the |Gas consumed|Rate per |Amount de-|Per Centage of Loss of | |Place where |in each Lamp|Meter Cu-|ducted for|Gas made. | |Gas Works |per Hour. |bic Feet |cleaning, | | |are situated. | |received |lighting, | | | | |for |extin- | | | | |Ditto. |guishing, | | | | | |providing | | | | | |Lamp | | | | | |Posts; &c.| | +--------------+------------+---------+----------+------------------------+ | | |s. d. |s. d. | | +--------------+------------+---------+----------+------------------------+ |Birmingham Gas|5 feet per |30 10 |18 0 |Receives net about 6_s._| |Company. |hour. |40 18 | |8_d._ per meter cubic | | | | | |feet. | +--------------+------------+---------+----------+------------------------+ |Birmingham and|Ditto. | 1 3-1/2|18 0 |Receives net about 5_s._| |Staffordshire.| | | |6_d._ per meter cubic | | | | | |feet. | +--------------+------------+---------+----------+------------------------+ |Macclesfield. |4 feet per | 3 0 |12 0 |Could not say. | | |hour. | | | | +--------------+------------+---------+----------+------------------------+ |Stockport. |Ditto. | 2 6 |12 6 |Ditto. | +--------------+------------+---------+----------+------------------------+ |Manchester. |1 foot, | 6 6 |nothing. |About 15 to 17-1/2 per | | |2 feet, per | 5 6 | |cent. receive about | | |hour. | | |7_s._ 4_d._ per meter | | | | | |cubic feet, public and | | | | | |private. Nearly all by | | | | | |meter. | +--------------+------------+---------+----------+------------------------+ |Liverpool Old |5 feet per | 4 4 |12 0 |Could not learn in the | |Company, 1834.|hour. | | |absence of the manager. | +--------------+------------+---------+----------+------------------------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel coal | | |similar to the Liverpool New Gas and Coal Company, pro- | | |ducing nearly similar results, which see. | +--------------+------------+---------+----------+------------------------+ |Liverpool New |3-1/2 feet | 5 6 |nothing. |Nearly all by meter. | |Gas and Coke, |per hour. | | | | |1835. | | | | | +--------------+------------+---------+----------+------------------------+ |Bradford, |5 feet per | 3 1 |12 6 |Receive 8_s._ per meter | |1834. |hour. | | |cubic feet, less 5-1/2 | | | | | |per cent. | +--------------+------------+---------+----------+------------------------+ |Leeds, 1834. |4 feet per | 5 2 | 3 10 |Receive for public and | | |hour. | | |private 6_s._ 8_d._ per | | | | | |meter cubic feet. Public| | | | | |5_s._, private 7_s._; | | | | | |meters used to 5 to 1 | | | | | |for private rental. | +--------------+------------+---------+----------+------------------------+ |Sheffield, |Ditto. | 3 2-1/2|18 0 |Receive for public and | |1835. | | | |private lts. 5_s._ per | | | | | |meter cubic feet. Public| | | | | |3_s._ 2-1/2_d._, private| | | | | |5_s._ 9-1/2_d._ Few | | | | | |meters used. | +--------------+------------+---------+----------+------------------------+ |Leicester, |5 feet per | 3 4-3/4| 7 0 |Not sufficiently long, | |1837. |hour. | | |at 7_s._ 6_d._ | +--------------+------------+---------+----------+------------------------+ |Derby, 1834. |Ditto. | 4 0 | ---- |Lose about 17-1/2 per | | | |nearly. | |cent. | +--------------+------------+---------+----------+------------------------+ |Nottingham, |Ditto. | 3 0 | ---- |Could not learn. | |1834. | |nearly. | | | +--------------+------------+---------+----------+------------------------+ |London, 1834. |4 feet per | 4 0 |12 0 |Receive for public and | | |hour. | | |private lights 7_s._ | | | | | |public, 4_s._ private, | | | | | |8_s._ few meters used. | +--------------+------------+---------+----------+------------------------+ |Ditto, 1837. |Ditto. | 4 0 |12 0 |Ditto. | +--------------+------------+---------+----------+------------------------+

+--------------+--------------+--------+---------+---------+--------+ |Name of the |Greatest Quan-|Duration|Method of|Number of|Specific| |Place where |tity of Gas |of Char-|Purifica-|Gas |Gravity | |Gas Works |delivered in |ges. |tion. |Holders. |of the | |are situated. |One Night. | | | |Gas. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +--------------+--------------+--------+---------+---------+--------+ | |Cubic Feet. | | | | | +--------------+--------------+--------+----------+--------+--------+ |Birmingham Gas|48 millions in|6 hours.|Dry lime.|4, and 2 |·453 | |Company. |the year. | | |in the | | | | | | |town, and| | | | | | |large new| | | | | | |gas | | | | | | |station. | | +--------------+--------------+--------+---------+---------+--------+ |Birmingham and|85 millions in|Ditto. |Ditto. |6, and 6 |·455 | |Staffordshire.|the year. | | |in the | | | | | | |town 7 | | | | | | |miles | | | | | | |off. | | +--------------+--------------+--------+---------+---------+--------+ |Macclesfield. |80,000. Total |8 hours.|Ditto. |3 gas |Not | | |for year about| | |holders. |taken. | | |15 millions. | | | | | +--------------+--------------+--------+---------+---------+--------+ |Stockport. |65,000. Total |Ditto. |Ditto. |4 gas |·539 | | |for year about| | |holders. | | | |12 millions. | | | | | +--------------+--------------+--------+---------+---------+--------+ |Manchester. |500,000. Total|6 hours.|Wet lime.|10 gas |·534 | | |for year 100 | | |holders, | | | |millions. | | |and 2 in | | | | | | |the town.| | +--------------+--------------+--------+---------+---------+--------+ |Liverpool Old |360,000. Total|8 hours,|Wet and |8 gas |·462 | |Company, 1834.|for year |large |dry lime,|holders | | | |72 millions. |retorts |princi- |in all, 4| | | | |holding |pally |in the | | | | |6 cwt. |dry. |town, | | | | |each. | |1000 | | | | | | |yards | | | | | | |off the | | | | | | |works. | | +--------------+--------------+--------+---------+---------+--------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel | | |coal similar to the Liverpool New Gas and Coal Com- | | |pany, producing nearly similar results, which see. | +--------------+--------------+--------+---------+---------+--------+ |Liverpool New |Not suffi- |4 hours.|Wet lime.|2 large |·580 | |Gas and Coke, |ciently long | | |gas | | |1835. |at work. | | |holders. | | +--------------+--------------+------------------+---------+--------+ |Bradford, |42,500. Total |8 hours.|Dry lime.|4 gas |·420 | |1834. |for year | | |holders. | | | |8,619,000. | | | | | +--------------+--------------+--------+---------+---------+--------+ |Leeds, 1834. |176,000. Total|6 hours.|Ditto. |5 gas |·530 | | |for year 31 | | |holders. | | | |millions. | | | | | +--------------+--------------+--------+---------+---------+--------+ |Sheffield, |220,000. Total|Ditto. |Ditto. |4 gas |·466 | |1835. |for year 40 | | |holders, | | | |millions. | | |and 2 | | | | | | |more | | | | | | |erecting.| | +--------------+--------------+--------+---------+---------+--------+ |Leicester, |Total for year|Ditto. |Ditto. |3 gas |·528 | |1837. |18 millions. | | |holders, | | | | | | |and 1 | | | | | | |erecting.| | +--------------+--------------+--------+---------+---------+--------+ |Derby, 1834. |Ditto. |Ditto. |Wet lime.|4 gas |·448 | | | | | |holders. | | +--------------+--------------+--------+---------+---------+--------+ |Nottingham, |Ditto. |Ditto. |Ditto. | ---- |·424 | |1834. | | | | | | +--------------+--------------+--------+---------+---------+--------+ |London, 1834. |Total for year|Ditto. |Ditto. |130 gas |·412 | | |1000 millions.| | |holders. | | | |Longest night | | | | | | |4,910,000. | | | | | +--------------+--------------+--------+---------+---------+--------+ |Ditto, 1837. |Total for year|Ditto. |Ditto. |176 gas |·412 | | |1460 millions.| | |holders. | | | |Longest night | | | | | | |7,120,000. | | | | | +--------------+--------------+--------+---------+---------+--------+

+--------------+---------+-----------+--------+-------+-------------+ |Name of the |Distance |Gas equal |Gas |Gas |Height of Gas| |Place where |of Candle|to Candles.|consumed|Flame |Flame equal | |Gas Works |from |Gas burnt |per Hour|reduced|to Light | |are situated. |Shadow. |in a single|with a |to Can-|from Candle. | | | |Jet Four |Four- |dle | | | | |Inches |Inch |burnt | | | | |high. |Flame. |per | | | | | | |Hour. | | +--------------+---------+-----------+--------+-------+-------------+ | |Inch. |Candles |_Cu. |_Cu. |Inch. | | | | |ft. |ft. | | +--------------+---------+-----------+--------+-------+-------------+ |Birmingham Gas|72 |1,929 |1·22 | ·8 |2-1/2 | |Company. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Birmingham and|72 |1,929 |1·22 | ·8 |2-1/2 | |Staffordshire.| | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Macclesfield. |70 | 204 |Not | ·8 |2-3/4 | | | | |taken. | | | +--------------+---------+-----------+--------+-------+-------------+ |Stockport. |64 |2,441 | ·85 | ·55 |2-5/8 | +--------------+---------+-----------+--------+-------+-------------+ |Manchester. |66 |2,295 | ·825 | ·475 |2-1/4 | +--------------+---------+-----------+--------+-------+-------------+ |Liverpool Old |75 |1,777 |1·1 | ·75 |2-5/8 | |Company, 1834.| | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Ditto ditto. |In 1835 this Company resorted to the use of cannel | | |coal similar to the Liverpool New Gas and Coal Com- | | |pany, producing nearly similar results, which see. | +--------------+---------+-----------+--------+-------+-------------+ |Liverpool New |55 |3,306 | ·9 | ·45 |2 | |Gas and Coke, | | | | | | |1835. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Bradford, |78 |1,643 | ·12 | ·9 |3 | |1834. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Leeds, 1834. |67 |2,228 | ·855 | ·51 |2-1/4 | +--------------+---------+-----------+--------+-------+-------------+ |Sheffield, |74 |1,826 |1·04 | ·735 |2-3/4 | |1835. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Leicester, |74 |1,826 |1·1 | ·75 |2-3/4 | |1837. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |Derby, 1834. |83 |1,453 |1·2 | ·925 |3 | +--------------+---------+-----------+--------+-------+-------------+ |Nottingham, |90 |1,234 |1·3 |1·175 |3 | |1834. | | | | | | +--------------+---------+-----------+--------+-------+-------------+ |London, 1834. |80 |1,562 |1·13 | ·84 |2-3/4 | +--------------+---------+-----------+--------+-------+-------------+ |Ditto, 1837. |80 |1,562 |1·13 | ·84 |2-3/4 | +--------------+---------+-----------+--------+-------+-------------+

A TABLE shewing the Rate per Thousand Cubic feet received for any Burner consuming from 1/2 a Cubic foot to 10 Cubic feet per hour, at any given price per annum, and to the times below stated. By Joseph Hedley, Esq.

+----------------------+------+-----------------+-----------------+ | | | Single Jets. | 2 Jets. | | | | | | | | No. +-----+-----+-----+-----+-----+-----+ | Time of Burning | of | Cub.| Cub.| Cub.|Cub. |Cub. |Cub. | | per annum. |Hours.| ft. | ft. | ft. | ft. | ft. | ft. | | |[30] | 1/2 | 3/4 | 1 |1-1/4|1-1/2|1-3/4| +----------------------+------+-----+-----+-----+-----+-----+-----+ |From Dusk to 8 o’clock| 781 |2·56 |1·706|1·28 |1·026|·853 |·731 | | ditto and Sundays| 902 |2·216|1·478|1·108| ·887|·739 |·633 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1050 |1·904|1·27 | ·952| ·762|·635 |·544 | | ditto and Sundays| | | | | | | | | and from ditto | 1172 |1·706|1·138| ·853| ·682|·569 |·487 | | 9 o’clock | 1054 |1·896|1·264| ·948| ·759|·632 |·542 | | ditto and Sundays| 1221 |1·638|1·092| ·819| ·675|·546 |·463 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1323 |1·510|1·066| ·755| ·604|·503 |·431 | | ditto and Sundays| | | | | | | | | and from ditto | 1490 |1·342| ·894| ·671| ·536|·447 |·383 | | 10 o’clock | 1367 |1·462| ·974| ·731| ·585|·487 |·418 | | ditto and Sundays| 1586 |1·26 | ·84 | ·63 | ·504|·42 |·36 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1636 |1·222| ·814| ·611| ·489|·407 |·349 | | ditto and Sundays| | | | | | | | | and from ditto | 1855 |1·078| ·718| ·539| ·431|·359 |·308 | | 11 o’clock | 1680 |1·19 | ·794| ·595| ·476|·397 |·34 | | ditto and Sundays| 1951 |1·024| ·682| ·512| ·409|·341 |·293 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1949 |1·026| ·684| ·513| ·41 |·342 |·294 | | ditto and Sundays| | | | | | | | | and from ditto | 2220 | ·9 | ·6 | ·45 | ·36 |·3 |·257 | | 12 o’clock | 1993 |1· | ·668| ·502| ·4 |·334 |·287 | | ditto and Sundays| 2316 | ·862| ·574| ·432| ·345|·287 |·247 | | ditto and from 6 | | | | | | | | | o’clock mornings | 2262 | ·884| ·59 | ·442| ·353|·295 |·255 | | ditto and Sundays| | | | | | | | | and from ditto | 2585 | ·772| ·514| ·387| ·309|·257 |·221 | | 1 o’clock | 2306 | ·866| ·578| ·434| ·347|·289 |·247 | | ditto and Sundays| 2681 | ·746| ·498| ·373| ·298|·249 |·213 | | ditto and from 6 | | | | | | | | | o’clock mornings | 2575 | ·776| ·518| ·388| ·31 |·259 |·222 | | ditto and Sundays| | | | | | | | | and from ditto | 2950 | ·678| ·452| ·339| ·271|·226 |·193 | | All night | 4327 | ·462| ·308| ·231| ·185|·154 |·132 | +----------------------+------+-----+-----+-----+-----+-----+-----+

+----------------------+------+----------------+-----------------+ | | | 3 Jets. | Small Argand. | | | | | | | | No. +----+-----+-----+-----+-----+-----+ | Time of Burning | of |Cub.|Cub. |Cub. |Cub. |Cub. |Cub. | | per annum. |Hours.| ft.| ft. | ft. | ft. | ft. | ft. | | |[30] | 2 |2-1/2| 3 |3-1/2| 4 |4-1/2| +----------------------+------+----+-----+-----+-----+-----+-----+ |From Dusk to 8 o’clock| 781 |·64 |·5132|·4268|·3658|·3201|·2846| | ditto and Sundays| 902 |·554|·4434|·3695|·3168|·2771|·2464| | ditto and from 6 | | | | | | | | | o’clock mornings | 1050 |·476|·381 |·3174|·272 |·2381|·2116| | ditto and Sundays| | | | | | | | | and from ditto | 1172 |·426|·3412|·2844|·2438|·2133|·1896| | 9 o’clock | 1054 |·474|·3794|·3162|·271 |·2371|·2108| | ditto and Sundays| 1221 |·409|·3376|·273 |·234 |·2047|·182 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1323 |·378|·3022|·2519|·2158|·1889|·1678| | ditto and Sundays| | | | | | | | | and from ditto | 1490 |·335|·2684|·2236|·1918|·1675|·1492| | 10 o’clock | 1367 |·366|·2926|·2438|·209 |·1829|·1626| | ditto and Sundays| 1586 |·315|·2522|·2101|·1802|·1576|·14 | | ditto and from 6 | | | | | | | | | o’clock mornings | 1636 |·305|·2444|·2037|·1746|·1528|·1358| | ditto and Sundays| | | | | | | | | and from ditto | 1855 |·269|·2156|·1796|·154 |·1347|·1198| | 11 o’clock | 1680 |·297|·238 |·1984|·17 |·1488|·133 | | ditto and Sundays| 1951 |·256|·2048|·1707|·1466|·1281|·1138| | ditto and from 6 | | | | | | | | | o’clock mornings | 1949 |·256|·2052|·171 |·1466|·1282|·114 | | ditto and Sundays| | | | | | | | | and from ditto | 2220 |·225|·1802|·1501|·1286|·1126|·1 | | 12 o’clock | 1993 |·251|·2006|·1672|·1434|·1254|·1114| | ditto and Sundays| 2316 |·215|·1726|·1439|·1236|·1079|·0958| | ditto and from 6 | | | | | | | | | o’clock mornings | 2262 |·221|·1768|·1476|·1274|·1105|·0982| | ditto and Sundays| | | | | | | | | and from ditto | 2585 |·193|·1546|·1289|·1104|·0967|·0858| | 1 o’clock | 2306 |·217|·1734|·1445|·1238|·1080|·0962| | ditto and Sundays| 2681 |·186|·1492|·1243|·1066|·0932|·0828| | ditto and from 6 | | | | | | | | | o’clock mornings | 2575 |·194|·1552|·1294|·111 |·0971|·0862| | ditto and Sundays| | | | | | | | | and from ditto | 2950 |·169|·1356|·113 |·0968|·0847|·0754| | All night | 4327 |·115|·6924|·077 |·066 |·0578|·0515| +----------------------+------+----+-----+-----+-----+-----+-----+

+----------------------+------+-----------------+-----------------+ | | | Large Argand. |Fancy and extra- | | | | |vagant Burners. | | | No. +-----+-----+-----+-----+-----+-----+ | Time of Burning | of |Cub. |Cub. |Cub. |Cub. |Cub. |Cub. | | per annum. |Hours.| ft. | ft. | ft. | ft. | ft. | ft. | | |[30] | 5 | 6 | 7 | 8 | 9 | 10 | +----------------------+------+-----+-----+-----+-----+-----+-----+ |From Dusk to 8 o’clock| 781 |·2561|·2134|·1829|·16 |·1423|·128 | | ditto and Sundays| 902 |·2217|·1848|·1584|·1383|·1232|·1108| | ditto and from 6 | | | | | | | | | o’clock mornings | 1050 |·1905|·1587|·136 |·119 |·1058|·0952| | ditto and Sundays| | | | | | | | | and from ditto | 1172 |·1706|·1422|·1219|·1067|·0948|·0853| | 9 o’clock | 1054 |·1897|·1581|·1355|·1185|·1054|·0948| | ditto and Sundays| 1221 |·1638|·1365|·117 |·1024|·091 |·0819| | ditto and from 6 | | | | | | | | | o’clock mornings | 1323 |·1511|·1259|·1079|·0945|·0839|·0755| | ditto and Sundays| | | | | | | | | and from ditto | 1490 |·1312|·1118|·0959|·0839|·0746|·0671| | 10 o’clock | 1367 |·1463|·1219|·1045|·0914|·0813|·0731| | ditto and Sundays| 1586 |·1261|·1051|·0901|·0789|·07 |·0630| | ditto and from 6 | | | | | | | | | o’clock mornings | 1636 |·1222|·1019|·0873|·0764|·0679|·0611| | ditto and Sundays| | | | | | | | | and from ditto | 1855 |·1078|·0898|·077 |·0674|·0599|·0539| | 11 o’clock | 1680 |·119 |·0992|·085 |·0744|·0665|·0595| | ditto and Sundays| 1951 |·1024|·0854|·0733|·064 |·0569|·0512| | ditto and from 6 | | | | | | | | | o’clock mornings | 1949 |·1026|·0855|·0733|·0641|·057 |·0513| | ditto and Sundays| | | | | | | | | and from ditto | 2220 |·0981|·0751|·0643|·0563|·05 |·045 | | 12 o’clock | 1993 |·1003|·0836|·0717|·0627|·0557|·0502| | ditto and Sundays| 2316 |·0863|·0719|·0618|·0539|·0479|·0432| | ditto and from 6 | | | | | | | | | o’clock mornings | 2262 |·0884|·0737|·0637|·0552|·0491|·0442| | ditto and Sundays| | | | | | | | | and from ditto | 2585 |·0773|·0645|·0552|·0483|·0429|·0387| | 1 o’clock | 2306 |·0867|·0723|·0619|·0542|·0481|·0434| | ditto and Sundays| 2681 |·0746|·0621|·0533|·0466|·0414|·0373| | ditto and from 6 | | | | | | | | | o’clock mornings | 2575 |·0776|·0647|·0555|·0485|·0431|·0388| | ditto and Sundays| | | | | | | | | and from ditto | 2950 |·0678|·0565|·0484|·0424|·0377|·0339| | All night | 4327 |·0462|·0385|·033 |·0289|·0257|·0231| +----------------------+------+-----+-----+-----+-----+-----+-----+

To use the Table.--Select the hour to which it is agreed the gas is to burn,--9, 10, 11 o’clock, Sundays, &c., as the case may be, and the description of the burner.--Multiply the decimal number opposite to it by the amount in shillings agreed to be paid per annum, and the product will be the sum received per m. cubic feet for the gas.

Example.--Suppose a small argand which should burn 3-1/2 feet per hour, is agreed for till 9 o’clock at 2_l._ per annum. Look along the line of 9 o’clock till you arrive at the column of 3-1/2 feet per hour, and you find the number, ·271. Multiply this number by 40_s._ and the result gives 10_s._ 10_d._ per m. cubic feet. But suppose instead of keeping to 9 o’clock the party burns till 1 o’clock, Sundays and mornings, and by enlarging the holes or height of flame consumes 8 cubic feet of gas per hour; then you have the number, ·0424, which multiplied by 40_s._, still the price paid, gives 1_s._ 8_d._ per m. cubic feet only, and so on for any greater or lesser variation of the agreement.

[30] The “number of hours” includes 1/4 of an hour allowed for shutting shops, and 1 hour’s extra burning on Saturday nights.

GENERAL SUMMARY.

For lighting London and its suburbs with gas, there are--

18 public gas works.

12 do. companies.

2,800,000_l._ capital employed in works, pipes, tanks, gas-holders, apparatus.

450,000_l._ yearly revenue derived.

180,000 tons of coals used in the year for making gas.

1,460,000,000 cubic feet of gas made in the year.

134,300 private burners supplied to about 40,000 consumers.

30,400 public or street do. N. B. about 2650 of these are in the city of London.

380 lamplighters employed.

176 gas-holders; several of them double ones, capable of storing 5,500,000 cubic feet.

890 tons of coals used in the retorts on the shortest day, in 24 hours.

7,120,000 cubic feet of gas used in longest night, say 24th December.

About 2500 persons are employed in the metropolis alone, in this branch of manufacture.

Between 1822 and 1827 the quantity nearly doubled itself, and that in 5 years.

Between 1827 and 1837 it doubled itself again.

Mr. Kirkham, engineer, obtained a patent, in June, 1837, for an improved mode of removing the carbonaceous incrustation from the internal surfaces of gas retorts. He employs a jet or jets of heated atmospheric air, or other gases containing oxygen, which he impels with force into the interior of such retorts as have become incrusted in consequence of the decomposition of the coal. The retort is to be kept thoroughly red hot during the application of the proposed jets. An iron pipe, constructed with several flexible joints, leading from a blowing machine, is bent in such a way as to allow its nozzle end to be introduced within the retort, and directed to any point of its surface.

I should suppose that air, even at common temperatures, applied to a retort ignited to the pitch of making gas, would burn away the incrustations; but hot air will, no doubt, be more powerful.

GAS-HOLDER; a vessel for containing and preserving gas, of which various forms are described by chemical writers.

GASOMETER, means properly a measurer of gas, though it is employed often to denote a recipient of gas of any kind. See the article GAS-LIGHT.

GAUZE WIRE CLOTH; is a textile fabric, either plane or tweelled, made of brass, iron, or copper wire, of very various degrees of fineness and openness of texture. Its chief uses are for sieves, and safety lamps.

GAY-LUSSITE, is a white mineral of a vitreous fracture, which crystallizes in oblique rhomboidal prisms; specific gravity from 1·93 to 1·95; scratches gypsum, but is scratched by calcspar; affords water by calcination; it consists of carbonic acid 28·66; soda, 20·44; lime, 17·70; water, 32·20; clay, 1·00. It is in fact, by my analysis, a hydrated soda-carbonate of lime in atomic proportions. This mineral occurs abundantly in insulated crystals, disseminated through the bed of clay which covers the urao, or native sesquicarbonate of soda, at Lagunilla in Colombia.

GELATINE; (Eng. and Fr.; Gallert, Leim, Germ.) is an animal product which is never found in the humours, but it may be obtained by boiling with water the soft and solid parts; as the muscles, the skin, the cartilages, bones, ligaments, tendons, and membranes. Isinglass consists almost entirely of gelatine. This substance is very soluble in boiling water; the solution forms a tremulous mass of jelly when it cools. Cold water has little action upon gelatine. Alcohol and tannin (tannic acid, see GALL-NUTS) precipitate gelatine from its solution; the former by abstracting the water, the latter by combining with the substance itself into an insoluble compound; of the nature of leather. No other acid, except the tannic, and no alkali possesses the property of precipitating gelatine. But chlorine and certain salts render its solution more or less turbid; as the nitrate and bi-chloride of mercury, the proto-chloride of tin, and a few others. Sulphuric acid converts a solution of gelatine at a boiling heat into sugar. See LIGNEOUS FIBRE. Gelatine consists of carbon, 47·88; hydrogen, 7·91; oxygen, 27·21. See GLUE and ISINGLASS.

GEMS, are precious stones, which, by their colour, limpidity, lustre, brilliant polish, purity, and rarity, are sought after as objects of dress and decoration. They form the principal part of the crown jewels of kings, not only from their beauty, but because they are supposed to comprize the greatest value in the smallest bulk; for a diamond, no larger than a nut or an acorn, may be the representative sign of the territorial value of a whole country, the equivalent in commercial exchange of a hundred fortunes, acquired by severe toils and privations.

Among these beautiful minerals mankind have agreed in forming a select class, to which the title of gems or jewels has been appropriated; while the term precious stone is more particularly given to substances which often occur under a more considerable volume than fine stones ever do.

Diamonds, sapphires, emeralds, rubies, topazes, hyacinths, and chrysoberyls, are reckoned the most valuable gems.

Crystalline quartz, pellucid opalescent or of various hues, amethyst, lapis lazuli, malachite, jasper, agate, &c., are ranked in the much more numerous and inferior class of ornamental stones. These distinctions are not founded upon any strict philosophical principle, but are regulated by a conventional agreement, not very well defined; for it is impossible to subject these creatures of fashion and taste to the rigid subdivisions of science. We have only to consider the value currently attached to them, and take care not to confound two stones of the same colour, but which may be very differently prized by the virtuoso.

Since it usually happens that the true gems are in a cut and polished state, or even set in gold or silver, we are thereby unable to apply to them the criteria of mineralogical and chemical science. The cutting of the stone has removed or masked its crystalline character, and circumstances rarely permit the phenomena of double or single refraction to be observed; while the test by the blowpipe is inadmissible. Hence the only scientific resources that remain are the trial by electricity, which is often inconclusive; the degree of hardness, a criterion requiring great experience in the person who employs it; and, lastly, the proof by specific gravity, unquestionably one of the surest means of distinguishing the really fine gems from ornamental stones of similar colour. This proof can be applied only to a stone that is not set; but the richer gems are usually dismounted, when offered for sale.

This character of specific gravity may be applied by any person of common intelligence, with the aid of a small hydrostatic balance. If, for example, a stone of a fine crimson-red colour, be offered for sale, as an oriental ruby; the purchaser must ascertain if it be not a Siberian tourmaline, or ruby spinel. Supposing its weight in air to be 100 grains, if he finds it reduced to 69 grains, when weighed in water, he concludes that its bulk is equal to that of 31 grains of water, which is its loss of weight. Now, a real sapphire which weighs 100 grains in air, would have weighed 76·6 in water; a spinel ruby of 100 grains would have weighed 72·2 in water, and a Siberian tourmaline of 100 grains would have weighed only 69 grains in water. The quality of the stone in question is, therefore, determined beyond all dispute, and the purchaser may be thus protected from fraud.

The sard of the English jewellers (Sardoine, French) is a stone of the nature of agate, having an orange colour more or less deep, and passing by insensible shades into yellow, reddish, and brown; whence it has been agreed to unite under this denomination all the agates whose colour verges upon brown. It should be remarked, however, that the sard presents, in its interior and in the middle of its ground, concentric zones, or small nebulosities, which are not to be seen in the red cornelian, properly so called. The ancients certainly knew our sard, since they have left us a great many of them engraved, but they seem to have associated under the title sarda both the sardoine of the French, and our cornelians and calcedonies. Pliny says that the sarda came from the neighbourhood of a city of that name in Lydia, and from the environs of Babylon. Among the engraved sards which exist in the collection of antiques in the Bibliothèque Royale of Paris, there is an Apollo remarkable for its fine colour and great size. When the stone forms a part of the agate-onyx, it is called sardonyx. For further details upon Gems, and the art of cutting and engraving them, see LAPIDARY.

GEOGNOSY, means a knowledge of the structure of the earth; GEOLOGY, a description of the same. The discussion of this subject does not come within the province of this Dictionary.

GERMAN SILVER. See the latter end of the article COPPER.

GERMINATION; (Eng. and Fr.; Das Keimen, Germ.) is the first sprouting of a seed after it is sown, or when, after steeping, it is spread upon the malt floor. See BEER.

GIG MACHINES, are rotatory drums, mounted with thistles or wire teeth for teazling cloth. See WOOLLEN MANUFACTURE.

GILDING (Dorure, Fr.; Vergoldung, Germ.); is the art of coating surfaces with a thin film of gold. For a full discussion of this subject, see GOLD. Mr. Elkington, gilt toy maker, obtained a patent, in June, 1836, for gilding copper, brass, &c., by means of potash or soda combined with carbonic acid, and with a solution of gold. Dissolve, says he, 5 oz. troy of fine gold in 52 oz. avoirdupois of nitro-muriatic acid of the following proportions: viz. 21 oz. of pure nitric acid, of spec. grav. 1·45, 17 oz. of pure muriatic acid, of spec. grav. 1·15; with 14 oz. of distilled water.

The gold being put into the mixture of acids and water, they are to be heated in a glass or other convenient vessel till the gold is dissolved; and it is usual to continue the application of heat after this is effected, until a reddish or yellowish vapour ceases to rise.

The clear liquid is to be carefully poured off from any sediment which generally appears and results from a small portion of silver, which is generally found in alloy with gold. The clear liquid is to be placed in a suitable vessel of stone, pottery ware is preferred. Add to the solution of gold 4 gallons of distilled water, and 20 pounds of bicarbonate of potash of the best quality; let the whole boil moderately for 2 hours, the mixture will then be ready for use.

The articles to be gilded having been first perfectly cleaned from scale or grease, they are to be suspended on wires, conveniently for a workman to dip them in the liquid, which is kept boiling. The time required for gilding any particular article will depend on circumstances, partly on the quantity of gold remaining in the liquid, and partly on the size and weight of the article; but a little practice will readily give sufficient guidance to the workman.

Supposing the articles desired to be gilded be brass or copper buttons, or small articles for gilt toys, or ornaments of dress, such as earrings or bracelets, a considerable number of which may be strung on a hoop, or bended piece of copper or brass wire, and dipped into the vessel containing the boiling liquid above described, and moved therein, the requisite gilding will be generally obtained in from a few seconds to a minute; this is when the liquid is in the condition above described, and depending on the quality of the gilding desired; but if the liquid has been used some time, the quantity of gold will be lessened, which will vary the time of operating to produce a given effect, or the colour required, all which will quickly be observed by the workman; and by noting the appearance of the articles from time to time, he will know when the desired object is obtained, though it is desirable to avoid as much as possible taking the articles out of the liquid.

When the operation is completed, the workman perfectly washes the articles so gilded with clean water; they may then be submitted to the usual process of colouring.

If the articles be cast figures of animals, or otherwise of considerable weight, compared with the articles above mentioned, the time required to perform the process will be greater.

In case it is desired to produce what is called a dead appearance, it may be performed by several processes: the one usually employed is to dead the articles in the process of cleaning, as practised by brass-founders and other trades; it is produced by an acid, prepared for that purpose, sold by the makers under the term “deading aquafortis,” which is well understood.

It may also be produced by a weak solution of nitrate of mercury, applied to the articles previous to the gilding process, as is practised in the process of gilding with mercury, previous to spreading the amalgam, but generally a much weaker solution; or the articles having been gilded may be dipped in a solution of nitrate of mercury, and submitted to heat to expel the same, as is practised in the usual process of gilding.

It is desirable to remark, that much of the beauty of the result depends on the well cleaning of the articles, and it is better to clean them by the ordinary processes, and at once pass them into the liquid to be gilded. See GOLD, towards the end.

GIN, or Geneva, from Genievre (juniper), is a kind of ardent spirits manufactured in Holland, and hence called Hollands gin in this country, to distinguish it from British gin. The materials employed in the distilleries of Schiedam, are two parts of unmalted rye from Riga, weighing about 54 lbs. per bushel, and one part of malted bigg, weighing about 37 lbs. per bushel. The mash tun, which serves also as the fermenting tun, has a capacity of nearly 700 gallons, being about five feet in diameter at the mouth, rather narrower at the bottom, and 4-1/2 feet deep; the stirring apparatus is an oblong rectangular iron grid, made fast to the end of a wooden pole. About a barrel, = 36 gallons of water, at a temperature of from 162° to 168° (the former heat being best for the most highly dried rye), are put into the mash tun for every 1-1/2 cwt. of meal, after which the malt is introduced and stirred, and lastly the rye is added. Powerful agitation is given to the magma till it becomes quite uniform; a process which a vigorous workman piques himself upon executing in the course of a few minutes. The mouth of the tun is immediately covered over with canvas, and further secured by a close wooden lid, to confine the heat; it is left in this state for two hours. The contents being then stirred up once more, the transparent spent wash of a preceding mashing is first added, and next as much cold water as will reduce the temperature of the whole to about 85° F. The best Flanders yeast, which had been brought, for the sake of carriage, to a doughy consistence by pressure, is now introduced to the amount of one pound for every 100 gallons of the mashed materials.

The gravity of the fresh wort is usually from 33 to 38 lbs. per Dicas’ hydrometer; and the fermentation is carried on from 48 to 60 hours, at the end of which time the attenuation is from 7 to 4 lbs., that is, the specific gravity of the supernatant wash is from 1·007 to 1·004.

The distillers are induced by the scarcity of beer-barm in Holland, to skim off a quantity of the yeast from the fermenting tuns, and to sell it to the bakers, whereby they obstruct materially the production of spirit, though they probably improve its quality, by preventing its impregnation with yeasty particles; an unpleasant result which seldom fails to take place in the whiskey distilleries of the United Kingdom.

On the third day after the fermenting tun is set, the wash containing the grains is transferred to the still, and converted into low wines. To every 100 gallons of this liquor, two pounds of juniper berries, from 3 to 5 years old, being added along with about one quarter of a pound of salt, the whole are put into the low wine still, and the fine Hollands spirit is drawn off by a gentle and well-regulated heat, till the magma becomes exhausted; the first and the last products being mixed together; whereby a spirit, 2 to 3 per cent. above our hydrometer proof, is obtained, possessing the peculiar fine aroma of gin. The quantity of spirit varies from 18 to 21 gallons per quarter of grain; this large product being partly due to the employment of the spent wash of the preceding fermentation; an addition which contributes at the same time to improve the flavour.

For the above instructive details of the manufacture of genuine Hollands, I am indebted to Robert More, Esq., formerly of Underwood, distiller, who after studying the art at Schiedam, tried to introduce that spirit into general consumption in this country, but found the palates of our gin-drinkers too much corrupted to relish so pure a beverage.

GINNING, is the name of the operation by which the filaments of cotton are separated from the seeds. See COTTON MANUFACTURE.

GLANCE COAL, or anthracite, of which there are two varieties, the slaty and the conchoidal. See ANTHRACITE.

GLASS (Verre, Fr.; Glas, Germ.); is a transparent solid formed by the fusion of siliceous and alkaline matter. It was known to the Phenicians, and constituted for a long time an exclusive manufacture of that people, in consequence of its ingredients, natron, sand, and fuel, abounding upon their coasts. It is probable that the more ancient Egyptians were unacquainted with glass, for we find no mention of it in the writings of Moses. But according to Pliny and Strabo, the glass works of Sidon and Alexandria were famous in their times, and produced beautiful articles; which were cut, engraved, gilt, and stained of the most brilliant colours, in imitation of precious stones. The Romans employed glass for various purposes; and have left specimens in Herculaneum of window-glass, which must have been blown by methods analogous to the modern. The Phenician processes seem to have been learned by the Crusaders, and transferred to Venice in the 13th century, where they were long held secret, and formed a lucrative commercial monopoly. Soon after the middle of the 17th century, Colbert enriched France with the blown mirror glass manufacture.

Chance undoubtedly had a principal share in the invention of this curious fabrication, but there were circumstances in the most ancient arts likely to lead to it; such as the fusing and vitrifying heats required for the formation of pottery, and for the extraction of metals from their ores. Pliny ascribes the origin of glass to the following accident. A merchant-ship laden with natron being driven upon the coast at the mouth of the river Belus, in tempestuous weather, the crew were compelled to cook their victuals ashore, and having placed lumps of the natron upon the sand, as supports to the kettles, found to their surprise masses of transparent stone among the cinders. The sand of this small stream of Galilee, which runs from the foot of Mount Carmel, was in consequence supposed to possess a peculiar virtue for making glass, and continued for ages to be sought after and exported to distant countries for this purpose.

Agricola, the oldest author who has written technically upon glass, describes furnaces and processes closely resembling those employed at the present day. Neri, Kunckel, Henckel, Pott, Achard, and some other chemists, have since then composed treatises upon the subject; but Neri, Bosc, Antic, Loysel, and Allut, in the Encyclopédie Méthodique, are the best of the elder authorities.

The window-glass manufacture was first begun in England in 1557, in Crutched Friars, London; and fine articles of flint-glass were soon afterwards made in the Savoy House, Strand. In 1635 the art received a great improvement from Sir Robert Mansell, by the use of coal fuel instead of wood. The first sheets of blown glass for looking glasses and coach windows were made in 1673 at Lambeth, by Venetian artisans employed under the patronage of the Duke of Buckingham.

The casting of mirror-plates was commenced in France about the year 1688, by Abraham Thevart; an invention which gave rise soon afterwards to the establishment of the celebrated works of St. Gobin, which continued for nearly a century the sole place where this highly prized object of luxury was well made. In excellence and cheapness, the French mirror-plate has been, however, for some time rivalled by the English.

The analysis of modern chemists, which will be detailed in the course of this article, and the light thrown upon the manufacture of glass in general by the accurate means now possessed of purifying its several ingredients, would have brought the art to the highest state of perfection in this country, but for the vexatious interference and obstructions of our excise laws.

The researches of Berzelius having removed all doubts concerning the acid character of silica, the general composition of glass presents now no difficulty of conception. This substance consists of one or more salts; which are silicates with bases of potash, soda, lime, oxide of iron, alumina, or oxide of lead; in any of which compounds we can substitute one of these bases for another, provided that one alkaline base be left. Silica in its turn may be replaced by the boracic acid, without causing the glass to lose its principal characters.

Under the title glass are therefore comprehended various substances fusible at a high temperature, solid at ordinary temperatures, brilliant, generally more or less transparent, and always brittle. The following chemical distribution of glasses has been proposed.

1. Soluble glass; a simple silicate of potash or soda; or of both these alkalis.

2. Bohemian or crown glass; silicate of potash and lime.

3. Common window and mirror glass; silicate of soda and lime; sometimes also of potash.

4. Bottle glass; silicate of soda, lime, alumina and iron.

5. Ordinary crystal glass; silicate of potash and lead.

6. Flint glass; silicate of potash and lead; richer in lead than the preceding.

7. Strass; silicate of potash and lead; still richer in lead.

8. Enamel; silicate and stannate or antimoniate of potash or soda, and lead.

The glasses which contain several bases are liable to suffer different changes when they are melted or cooled slowly. The silica is divided among these bases, forming new compounds in definite proportions, which by crystallizing, separate from each other, so that the general mixture of the ingredients which constituted glass is destroyed. It becomes then very hard, fibrous, opaque, much less fusible, a better conductor of electricity and of heat; forming what Reaumur styled devitrified glass; and what is called after him, Reaumur’s porcelain.

This altered glass can always be produced in a more or less perfect state, by melting the glass and allowing it to cool very slowly; or merely by heating it to the softening pitch, and keeping it at this heat for some time. The process succeeds best with the most complex vitreous compounds, such as bottle glass; next with ordinary window glass; and lastly with glass of potash and lead.

This property ought to be kept constantly in view in manufacturing glass. It shows why in making bottles we should fashion them as quickly as possible with the aid of a mould, and reheat them as seldom as may be absolutely necessary. If it be often heated and cooled, the glass loses its ductility, becomes refractory, and exhibits a multitude of stony granulations throughout its substance. When coarse glass is worked at the enameller’s lamp, it is apt to change its nature in the same way, if the workman be not quick and expert at his business.

From these facts we perceive the importance of making a careful choice of the glass intended to be worked in considerable masses, such as the large object glasses of telescopes; as their annealing requires a very slow process of refrigeration, which is apt to cause devitrified specks and clouds. For such purposes, therefore, no other species of glass is well adapted except that with basis of potash and lead; or that with basis of potash and lime. These two form the best flint glass, and crown glass; and they should be exclusively employed for the construction of the object glasses of achromatic telescopes.

GLASS-MAKING, general principles of. Glass may be defined in technical phraseology, to be a transparent homogeneous compound formed by the fusion of silica with oxides of the alkaline, earthy, or common metals. It is usually colourless, and then resembles rock crystal, but is occasionally stained by accident or design with coloured metallic oxides. At common temperatures it is hard and brittle, in thick pieces; in thin plates or threads, flexible and elastic; sonorous when struck; fracture conchoidal, and of that peculiar lustre called vitreous; at a red heat, becoming soft, ductile and plastic. Besides glass properly so called, other bodies are capable of entering into vitreous fusion, as phosphoric acid, boracic acid, arsenic acid, as also certain metallic oxides, as of lead, and antimony, and several chlorides; some of which are denominated glasses. Impure and opaque vitriform masses are called slags; such are the productions of blast iron furnaces and many metallurgic operations.

Silica, formerly styled the earth of flints, which constitutes the basis of all commercial glass, is infusible by itself in the strongest fire of our furnaces; but its vitreous fusion is easily effected by a competent addition of potash or soda, either alone or mixed with lime or litharge. The silica, which may be regarded as belonging to the class of acids, combines at the heat of fusion with these bases, into saline compounds; and hence glass may be viewed as a silicate of certain oxides, in which the acid and the bases exist in equivalent proportions. Were these proportions, or the quantities of the bases which silica requires for its saturation at the melting point, exactly ascertained, we might readily determine beforehand the best proportions of materials for the glass manufacture. But as this is far from being the case, and as it is, moreover, not improbable that the capacity of saturation of the silica varies with the temperature, and that the properties of glass also vary with the bases, we must, in the present state of our knowledge, regulate the proportions rather by practice than by theory, though the latter may throw an indirect light upon the subject. For example, a good colourless glass has been found by analysis to consist of 72 parts of silica, 13 parts of potash, and 10 parts of lime, in 95 parts. If we reduce these numbers to the equivalent ratios, we shall have the following results; taking the atomic weights as given by Berzelius.

1 atom potash = 590 14·67 1 lime 356 8·84 3 silica 1722 42·79 } 71·49 2 silica 1155 28·70 } ---- ----- 3823 95·00

This glass would therefore have been probably better compounded with the just atomic proportions, to which it nearly approaches, viz. 71·49 silica, 14·67 potash, and 8·84 lime, instead of those given above as its actual constituents.

The proportions in which silica unites with the alkaline and other oxides are modified by the temperature as above stated; the lower the heat, the less silica will enter into the glass, and the more of the base will in general be required. If a glass which contains an excess of alkali be exposed to a much higher temperature than that of its formation, a portion of the base will be set free to act upon the materials of the earthen pot, or to be dissipated in fumes, until such a silicate remains as to constitute a permanent glass corresponding to that temperature. Hence the same mixture of vitrifiable materials will yield very different results, according to the heats in which it is fused and worked in the glass-house; and therefore the composition should always be referrible to the going of the furnace. When a species of glass which at a high temperature formed a transparent combination with a considerable quantity of lime, is kept for some time in fusion at a lower temperature, a portion of the lime unites with the silica into another combination of a semi-vitreous or even of a stony aspect, so as to spoil the transparency of the glass altogether. There is probably a supersilicate, and a subsilicate formed in such cases; the latter being much the more fusible of the two compounds. The Reaumur’s porcelain produced by exposing bottle glass to a red heat for 24 hours, is an example of this species of vitreous change in which new affinities are exercised at a lower temperature. An excess of silica, caused by the volatilization of alkaline matter with too strong firing, will bring on similar appearances.

The specific gravity of glass varies from 2·3 to 3·6. That of least specific gravity consists of merely silica and potash fused together; that with lime is somewhat denser, and with oxide of lead denser still. Plate glass made from silica, soda, and lime, has a specific gravity which varies from 2·50 to 2·6; crystal or flint glass from 3·0 to 3·6.

The power of glass to resist the action of water, alkalis, acids, air, and light, is in general the greater, the higher the temperature employed in its manufacture, the smaller the proportion of its fluxes, and the more exact the equivalent ratios of its constituents. When glass contains too much alkali, it is partially soluble in water. Most crystal glass is affected by having water boiled in it for a considerable time; but crown glass being poorer in alkali, and containing no lead, resists that action much longer, and is therefore better adapted to chemical operations. The affinity of glass for water, or its hygrometric attraction, is also proportional to the quantity of alkali which it contains. In general also potash glass is more apt to become damp than soda glass, agreeably to the respective hygrometric properties of these two alkalis, and also to the smaller proportion of soda than of potash requisite to form glass.

Air and light operate upon glass probably by their oxidizing property. Bluish or greenish coloured glasses become by exposure colourless, in consequence undoubtedly of the peroxidizement of the iron, to whose protoxide they owe their tint; other glasses become purple red from the peroxidizement of the manganese. The glasses which contain lead, suffer another kind of change in the air, if sulphuretted hydrogen be present; the oxide of lead is converted into a sulphuret, with the effect of rendering the surface of the glass opaque and iridescent. The more lead is in the glass, the quicker does this iridescence supervene. By boiling concentrated sulphuric acid in a glass vessel, or upon glass, we can ascertain its power of resisting ordinary menstrua. Good glass will remain smooth and transparent; bad glass will become rough and dim.

The brittleness of unannealed glass by change of temperature is sometimes very great. I have known a thick vessel to fly by vicissitudes of the atmosphere alone. This defect may be corrected by slowly heating the vessel in salt-water or oil to the highest pitch consistent with the nature of these liquids, and letting it cool very slowly. Within the limits of that range of heat, it will, in consequence of this treatment, bear alternations of temperature without cracking as before.

It has been said that glass made from silica and alkalis alone, will not resist the action of water, but that the addition of a little lime is necessary for this effect. In general 100 parts of quartzose sand require 33 parts of dry carbonate of soda for their vitrification, and 45 parts of dry carbonate of potash. But to make unchangeable alkaline glass, especially with potash, a smaller quantity of this than the above should be used, with a very violent heat. A small proportion of lime increases the density, hardness, and lustre of glass; and it aids in decomposing the alkaline sulphates and muriates always present in the pearl ash of commerce. From 7 to 20 parts of dry slaked lime have been added for 100 of silica, with advantage, it is said, in some German glass manufactories, where the alkaline matter is soda; for potass does not assimilate well with the calcareous earth.

In many glass works on the Continent, sulphate of soda is the form under which alkaline matter is introduced into glass. This salt requires the addition of 8 per cent. of charcoal to decompose and dissipate its acid; a result which takes place at a high heat, without the addition of any lime. 88 pounds of quartz-sand, 44 pounds of dry glauber salt, and 3 pounds of charcoal, properly mixed and fused, afford a limpid, fluent, and workable glass; with the addition of 17 pounds of lime, these materials fuse more readily into a plastic mass. If less carbon be added, the fusion becomes more tedious. The two following formulæ afford good glauber salt glass.

1. 2. ------ ---- Sand 100 60·3 Calcined sulphate of soda 50 26·8 Lime 20 10·8 Charcoal 2·65 2·1

The first mixture has been proved in the looking-glass manufactory of Neuhaus near Vienna, and the second by the experiments of Kirn. The fusion of the first requires 18, of the second 21 hours. The bluish-green tinge which these otherwise beautiful and brilliant glasses possess, is not removable by the ordinary means, such as manganese or arsenic, which decolour alkaline glass. When the sulphate of soda and charcoal are used in smaller proportions, the glass becomes more colourless. The tinge is no doubt owing to the sulphur combining with the oxide of sodium, in some such way as in the pigment ultramarine.

By a proper addition of galena (the native sulphuret of lead), to glauber salt and quartz sand, without charcoal, it is said a tolerably good crystal glass may be formed. The sulphuric acid of the salt is probably converted by the reaction of the sulphuret of lead into sulphurous acid gas, which is disengaged.

One atom of sulphuret of lead = 1495·67, is requisite to decompose 3 atoms of sulphate of soda = 2676. It is stated, on good authority, that a good colourless glass may be obtained by using glauber salt without charcoal, as by the following formula.

Quartz-sand 100 pounds Calcined glauber salt 24 Lime 20 Cullet of soda glass 12

The melting heat must be continued for 26-1/2 hours. A small quantity of the sand is reserved to be thrown in towards the conclusion of the process, in order to facilitate the expulsion of air bubbles. The above mixture will bear to be blanched by the addition of manganese and arsenic. The decomposition of the salt is in this case effected by the lime, with which the sulphuric acid first combines, is then converted into sulphurous acid, and dissipated. Glass made in this way was found by analysis to consist of 79 parts of silica, 12 lime, and 9·6 soda, without any trace of gypsum or sulphuric acid.

Glauber salt is partially volatilized by the heat of the furnace, and acts upon the arch of the oven and the tops of the pots. This is best prevented by introducing at first into the pots the whole of the salt mixed with the charcoal, the lime, and one fourth part of the sand; fusing this mixture at a moderate heat, and adding gradually afterwards the remainder of the sand, increasing the temperature at the same time. If we put in the whole ingredients together, as is done with potash glass, the sand and lime soon fall to the bottom, while the salt rises to the surface, and the combination becomes difficult and unequal.

Sulphate of potash acts in the same way as sulphate of soda.

Muriate of soda also, according to Kirn, may be used as a glass flux with advantage. The most suitable proportions are 4 parts of potash, 2 of common salt, and 3 of lime, agreeably to the following compositions:--

1. 2. ---- ---- Quartz-sand 60·0 75·1 Calcined carbonate of potash 17·8 19·1 Common salt 8·9 9·5 Lime 13·3 14·3

For No. 1., the melting heat must be 10 hours, which turns out a very pure, solid, good glass; for No. 2., 23 hours of the furnace are required. Instead of the potash, glauber salt may be substituted; the proportions being then 19·1 glauber salt, 9·5 muriate of soda, 14·3 lime, 75·1 sand, and 1·3 charcoal.

The oxide of lead is an essential constituent of the denser glasses, and may be regarded as replacing the lime, so as to form with the quartz-sand a silicate of lead. It assimilates best with purified pearl ash, on account of the freedom of this alkali from iron, which is present in most sodas.

Its atomic constitution may be represented as follows:--

+----------------------------+-----------------+--------+-------+ | | | Compu- |Analy- | | | |tation. | sis. | | | +--------+-------+ |Silicic acid | 5 atoms = 2877· | 59·19 | 59·20 | |Oxide of lead | 1 = 1394·5| 28·68 | 28·20 | |Potash | 1 = 590·0| 12·13 | 9·00 | |Oxides of iron and manganese| -- | -- | 1·40 | | | -------+--------+-------+ | | 4861·5| 100·00 |100·00 | +----------------------------+-----------------+--------+-------+

The above analysis by Berthier relates to a specimen of the best English crystal glass, perfectly colourless and free from air-bubbles. This kind of glass may however take several different proportions of potash and silica to the oxide of lead.

The composition of mirror plate, as made on the Continent, is as follows:--

White quartz-sand 300 pounds Dry carbonate of soda 100 Lime slaked in the air 43 Cullet, or old glass 300

The manganese should not exceed one half per cent. of the weight of the soda.

Optical glass requires to be made with very peculiar care. It is of two different kinds; namely, crown glass and flint glass. The latter contains a considerable proportion of lead, in order to give it an increased dispersive power upon the rays of light, in proportion to its mean refractive power.

Optical crown glass should be perfectly limpid, and have so little colour, that a pretty thick piece of it may give no appreciable tinge to the rays of light. It should be exempt from striæ or veins as well as air-bubbles, and have not the slightest degree of milkiness. It should moreover preserve these qualities when worked in considerable quantities. Potash is preferable to soda for making optical crown glass, because the latter alkali is apt to make a glass which devitrifies and becomes opalescent, by long exposure to heat in the annealing process. A simple potash silicate would be free from this defect, but it would be too attractive of moisture, and apt to decompose eventually by the humidity of the atmosphere. It should therefore contain a small quantity of lime, and as little potash as suffices for making a perfect glass at a pretty high temperature. It is probably owing to the high heats used in the English crown glass works, and the moderate quantity of alkali (soda) which is employed, that our crown glass has been found to answer so well for optical purposes.

PRACTICAL DETAILS OF THE MANUFACTURE OF GLASS.

The Venetians were the first in modern times who attained to any degree of excellence in the art of working glass, but the French became eventually so zealous of rivalling them, particularly in the construction of mirrors, that a decree was issued by the court of France, declaring not only that the manufacture of glass should not derogate from the dignity of a nobleman, but that nobles alone should be masters of glass-works. Within the last 30 or 40 years, Great Britain has made rapid advances in this important art, and at the present day her pre-eminence in every department hardly admits of dispute.

There are five different species of glass, each requiring a peculiar mode of fabrication, and peculiar materials: 1. The coarsest and simplest form of this manufacture is bottle glass. 2. Next to it in cheapness of material maybe ranked broad or spread window glass. An improved article of this kind is now made near Birmingham, under the name of British or German plate. 3. Crown glass comes next, or window glass, formed in large circular plates or discs. This glass is peculiar to Great Britain. 4. Flint glass, crystal glass, or glass of lead. 5. Plate or fine mirror glass.

The materials of every kind of glass are vitrified in pots made of a pure refractory clay; the best kind of which is a species of shale or slate clay dug out of the coal-formation near Stourbridge. It contains hardly any lime or iron, and consists of silica and alumina in nearly equal proportions. The masses are carefully picked, brushed, and ground under edge iron wheels of considerable weight, and sifted through sieves having 20 meshes in the square inch. This powder is moistened with water (best hot), and kneaded by the feet or a loam-mill into an uniform smooth paste. A large body of this dough should be made up at a time, and laid by in a damp cellar to ripen. Previously to working it into shapes, it should be mixed with about a fourth of its weight of cement of old pots, ground to powder. This mixture is sufficiently plastic, and being less contractile by heat, forms more solid and durable vessels. Glass-house pots have the figure of a truncated cone, with the narrow end undermost; those for bottle and window-glass, being open at top, about 30 inches diameter at bottom, 40 inches at the mouth, and 40 inches deep; but the flint-glass pots are covered in at top with a dome-cap, having a mouth at the side, by which the materials are introduced, and the glass is extracted. Bottle and crown-house pots are from 3 to 4 inches thick; those for flint-houses are an inch thinner, and of proportionally smaller capacity.

The well-mixed and kneaded dough is first worked upon a board into a cake for the bottom; over this the sides are raised, by laying on its edges rolls of clay above each other with much manual labour, and careful condensation. The clay is made into lumps, is equalized, and slapped much in the same way as for making POTTERY. The pots thus fashioned must be dried very prudently, first in the atmospheric temperature, and finally in a stove floor, which usually borrows its heat directly from the glass-house. Before setting the pots in the furnace, they are annealed during 4 or 5 days, at a red heat in a small reverberatory vault, made on purpose. When completely annealed, they are transferred with the utmost expedition into their seat in the fire, by means of powerful tongs supported on the axle of an iron-wheel carriage frame, and terminating in a long lever for raising them and swinging them round. The pot-setting is a desperate service, and when unskilfully conducted without due mechanical aids, is the forlorn hope of the glass-founder.--Quæque ipse miserrima vidi. The celebrated chemist, Dr. Irvine, caught his last illness by assisting imprudently at this formidable operation. The working breast of the hot furnace must be laid bare so as to open a breach for the extraction of the faulty pot, and the insertion of the fresh one, both in a state of bright incandescence. It is frightful to witness the eyes and fuming visages of the workmen, with the blackening and smoking of their scorched woollen clothes, exposed so long to the direct radiations of the flame. A light mask and sack dress coated with tinfoil, would protect both their faces and persons from any annoyance, at a very cheap rate.

The glass-houses are usually built in the form of a cone, from 60 to 100 feet high, and from 50 to 80 feet in diameter at the base. The furnace is constructed in the centre of the area, above an arched or groined gallery which extends across the whole space, and terminates without the walls, in large folding doors. This cavern must be sufficiently high to allow labourers to wheel out the cinders in their barrows. The middle of the vaulted top is left open in the building, and is covered over with the grate-bars of the furnace.

1. Bottle glass.--The bottle-house and its furnace resemble nearly fig. 505. The furnace is usually an oblong square chamber, built of large fire-bricks, and arched over with fire-stone, a siliceous grit of excellent quality extracted from the coal measures of Newcastle. This furnace stands in the middle of the area; and has its base divided into three compartments. The central space is occupied by the grate-bars; and on either side is the platform or fire-brick siege, (seat,) raised about 12 inches above the level of the ribs upon which the pots rest. Each siege is about 3 feet broad.

In the sides of the furnace, semi-circular holes of about a foot diameter are left opposite to, and a little above the top of, each pot, called working holes, by which the workmen shovel in the materials, and take out the plastic glass. At each angle of the furnace there is likewise a hole of about the same size, which communicates with the calcining furnace of a cylindrical form, dome-shaped at top. The flame that escapes from the founding or pot-furnace is thus economically brought to reverberate on the raw materials of the bottle glass, so as to dissipate their carbonaceous or volatile impurities, and convert them into a frit. A bottle-house has generally eight other furnaces or fire-arches; of which six are used for annealing the bottles after they are blown, and two for annealing the pots, before setting them in the furnace.

The laws of this country till lately prohibited the use for making common bottles of any fine materials. Nothing but the common river sand, and soap-boilers’ waste, was allowed. About 3 parts of waste, consisting of the insoluble residuum of kelp, mixed with lime and a little saline substance, were used for 1 part of sand. This waste was first of all calcined in two of the fire arches or reverberatories reserved for that purpose, called the coarse arches, where it was kept at a red heat, with occasional stirring, from 24 to 30 hours, being the period of a journey or journée, in which the materials could be melted and worked into bottles. The roasted soap-waste was then withdrawn, under the name of ashes, from its arch, coarsely ground, and mixed with its proper proportion of sand. This mixture was now put into the fine arch, and calcined during the working journey, which extended to 10 or 12 hours. Whenever the pots were worked out, that frit was immediately transferred into them in its ignited state, and the founding process proceeded with such despatch that this first charge of materials was completely melted down in 6 hours, so that the pots might admit to be filled up again with the second charge of frit, which was founded in 4 hours more. The heat was briskly continued, and in the course of from 12 to 18 hours, according to the size of the pots, the quality of the fuel, and the draught of the furnace, the vitrification was complete. Before blowing the bottles, however, the glass must be left to settle, and to cool down to the blowing consistency, by shutting the cave doors and feeding holes, so as to exclude the air from the fire-grate and the bottom of the hearth. The glass or metal becomes more dense, and by its subsidence throws up the foreign lighter earthy and saline matters in the form of a scum on the surface, which is removed with skimming irons. The furnace is now charged with coal, to enable it to afford a working heat for 4 or 5 hours, at the end of which time more fuel is cautiously added, to preserve adequate heat for finishing the journey.

It is hardly possible to convey in words alone a correct idea of the manipulations necessary to the formation of a wine bottle; but as the manufacturers make no mystery of this matter, any person may have an opportunity of inspecting the operation. Six people are employed at this task; one, called a gatherer, dips the end of an iron tube, about five feet long, previously made red-hot, into the pot of melted metal, turns the rod round so as to surround it with glass, lifts it out to cool a little, and then dips and turns it round again; and so in succession till a ball is formed on its end sufficient to make the required bottle. He then hands it to the blower, who rolls the plastic lump of glass on a smooth stone or cast-iron plate, till he brings it to the very end of the tube; he next introduces the pear-shaped ball into an open brass or cast-iron mould, shuts this together by pressing a pedal with his foot, and holding his tube vertically, blows through it, so as to expand the cooling glass into the form of the mould. Whenever he takes his foot from the pedal-lever, the mould spontaneously opens out into two halves, and falls asunder by its bottom hinge. He then lifts the bottle up at the end of the rod, and transfers it to the finisher, who, touching the glass-tube at the end of the pipe with a cold iron, cracks off the bottle smoothly at its mouth-ring. The finished bottles are immediately piled up in the hot annealing arch, where they are afterwards allowed to cool slowly for 24 hours at least. See BOTTLE MOULD.

2. Broad or spread window glass.--This kind of glass is called inferior window glass, in this country, because coarse in texture, of a wavy wrinkled surface, and very cheap, but on the Continent spread window glass, being made with more care, is much better than ours, though still far inferior in transparency and polish to crown glass, which has, therefore, nearly superseded its use among us. But Messrs. Chance and Hartley, of West Bromwich near Birmingham, have of late years mounted a spread-glass work, where they make British sheet glass, upon the best principles, and turn out an article quite equal, if not superior to any thing of the kind made either in France or Belgium. Their materials are those used in the crown-glass manufacture. The vitrifying mixture is fritted for 20 or 30 hours in a reverberatory arch, with considerable stirring and puddling with long-handled shovels and rakes; and the frit is then transferred by shovels while red hot, to the melting pots to be founded. When the glass is rightly vitrified, settled, and brought to a working heat, it is lifted out by iron tubes, as will be described under the article CROWN GLASS, blown into pears, which being elongated into cylinders, are cracked up along one side, parallel to the axis, by touching them with a cold iron dipped in water, and are then opened out into sheets. Glass cylinders are spread in France, and at West Bromwich, on a bed of smooth stone Paris-plaster, or laid on the bottom of a reverberatory arch; the cylinder being placed on its side horizontally, with the cracked line uppermost, gradually opens out, and flattens on the hearth. At one time, thick plates were thus prepared for subsequent polishing into mirrors; but the glass was never of very good quality; and this mode of making mirror-plate has accordingly been generally abandoned.

The spreading furnace or oven is that in which cylinders are expanded into tables or plates. It ought to be maintained at a brisk red heat, to facilitate the softening of the glass. The oven is placed in immediate connection with the annealing arch, so that the tables may be readily and safely transferred from the former to the latter. Sometimes the cylinders are spread in a large muffle furnace, in order to protect them from being tarnished by sulphureous and carbonaceous fumes.

Fig. 500. represents a ground plan of both the spreading and annealing furnace; fig. 501. is an oblong profile in the direction of the dotted line X X, fig. 500.

a is the fire-place; b b the canals or flues through which the flame rises into both furnaces; c the spreading furnace, upon whose sole is the spreading slab. d is the cooling and annealing oven; e e iron bars which extend obliquely across the annealing arch, and serve for resting the glass tables against, during the cooling. f f the channel along which the previously cracked cylinders are slid, so as to be gradually warmed; g the opening in the spreading furnace, for enabling the workmen to regulate the process; h a door in the annealing arch, for introducing the tools requisite for raising up and removing the tables.

In forming glass-plates by the extension of a cylinder into a plane, the workman first blows the lump of glass into the shape of an oblong pear, the length of which must be nearly equal to the length of the intended plate, and its diameter such, that the circumference when developed, will be equal to the breadth of the plate. He now rests the blowing-iron on a stool or iron bar, while an assistant with a pointed iron, pierces a hole into the extreme end of the pear, in the line of the blowing-pipe. This opening is then enlarged, by introducing the blade of a pair of spring-tongs, while the glass is turned round; and by skilful management, the end of the pear is eventually opened out into a cylindrical mouth. The workman next mounts upon a stool, and holds the blowing-iron perpendicularly. The blown cylinder is now cracked off, a punto rod of iron having been previously stuck to its one end, to form a spindle for working the other by. This rod has a flat disc on its end, or three prongs, which being dipped in melted glass, are applied to the mouth of the cylinder. By this as a handle, the glass cone is carried to the fire, and the narrow end being heated, is next opened by spring tongs, and formed into a cylinder of the same size as the other end. The cylinder thus equalized, is next cracked or slit down in its side with a pair of shears, laid on a smooth copper plate, detached from the iron rod, spread out by heat into a plane surface, and finally annealed. This series of transformations, is represented in fig. 502., at A, B, C, D, E, F, G, H.

Fig. 503. and 504. represent a Bohemian furnace in which excellent white window glass is founded. Fig. 503. is a longitudinal section of the glass and annealing furnace. Fig. 504. is the ground plan. a is the ash pit vaulted under the sole of the furnace; the fireplace itself is divided into three compartments; with a middle slab at d, which is hollowed in the centre, for collecting any spilt glass, and two hearth tiles or slabs b b. c c are the draught or air holes; e e are arches upon which the bearing slabs f f partly rest. In the middle between these arches, the flame strikes upwards upon the pots g g, placed as closely together as possible, for economy of room. h is the breast wall of the furnace; i, fig. 504., the opening through which the pots are introduced; it is bricked up as soon as they are set. k k, is the base of the cone or dome of the furnace; l l l, the working orifices, which are made larger or smaller according to the size of the glass articles to be made. m is the flue which leads to the annealing stove n, with an arched door. Exterior to this, there is usually a drying kiln not shown in the figure; and there are adjoining stoves called arches, for drying and annealing the new pots before they are set.

The cooling or annealing arch, or leer, is often built independent of the glass-house furnace, is then heated by a separate fire-place, and constructed like a very long reverberatory furnace. See COPPER.

The leer pans or trays of sheet iron, are laid upon its bottom in an oblong series, and hooked to each other.

3. Crown-glass.--The crown-glass house with its furnace is represented in fig. 505., where the blowing operation is shewn on the one side of the figure, and the flashing on the other. The furnace is usually constructed to receive 4 or 6 pots, of such dimensions as to make about a ton of glass each at a time. There are, however, several subsidiary furnaces to a crown-house. 1. A reverberatory furnace or calcar, for calcining or fritting the materials; 2. a blowing furnace, for blowing the pear-shaped balls made at the pot-holes, into large globes; 3. a flashing furnace, and bottoming hole for communicating a softening heat, in expanding the globe into a circular plate; 4. the annealing arch for the finished tables; 5. the reverberatory oven for annealing the pots prior to their being set upon the founding siege.

The materials of crown glass used to be, fine sand, by measure 5 parts, or by weight 10; ground kelp by measure 11 parts, or by weight 16-1/2; but instead of kelp, soda ash is now generally employed. From 6 to 8 cwt. of sand, lime, and soda-ash, mixed together in wooden boxes with a shovel, are thrown on the sole of a large reverberatory, such as is represented in the article COPPER. Here the mixture is well worked together, with iron paddles, flat shovels, and rakes with long handles; the area of this furnace being about 6 feet square, and the height 2 feet. The heat soon brings the materials to a pasty consistence, when they must be diligently turned over, to favour the dissipation of the carbon, sulphur, and other volatile matters of the kelp or soda ash, and to incorporate the fixed ingredients uniformly with the sand. Towards the end of 3 hours, the fire is considerably raised, and when the fourth hour has expired, the fritting operation is finished. The mass is now shovelled or raked out into shallow cast-iron square cases, smoothed down, and divided before it hardens by cooling, into square lumps, by cross sections with the spade. These frit-bricks are afterwards piled up in a large apartment for use; and have been supposed to improve with age, by the efflorescence of their saline constituents into carbonate of soda on their surface.

The founding-pots are filled up with these blocks of frit, and the furnace is powerfully urged by opening all the subterranean passages to its grate, and closing all the doors and windows of the glass-house itself. After 8 or 10 hours the vitrification has made such progress, and the blocks first introduced are so far melted down, that another charge of frit can be thrown in, and thus the pot is fed with frit till the proper quantity is used. In about 16 hours the vitrification of the frit has taken place, and a considerable quantity, amounting often to the cwt. of liquid saline matter floats over the glass. This salt is carefully skimmed off into iron pots with long ladles. It is called Sandiver or Glass-gall, and consists usually of muriate of soda, with a little sulphate. The pot is now ready for receiving the topping of cullet, which is broken pieces of window glass, to the amount of 3 or 4 cwt. This is shovelled in at short intervals; and as its pressure forces up the residuary saline matter, this is removed; for were it allowed to remain, the body of the glass would be materially deteriorated.

The heat is still continued for several hours till the glass is perfect, and the extrication of gas called the boil, which accompanies the fusion of crown glass, has nearly terminated, when the fire is abated, by shutting up the lower vault doors and every avenue to the grate, in order that the glass may settle fine. At the end of about 40 hours altogether, the fire being slightly raised by adding some coals, and opening the doors, the glass is carefully skimmed, and the working of the pots commences.

Before describing it, however, we may state that the marginal figure 506. shews the base of the crown-house cone, with the four open pots in two ranges on opposite sides of the furnace, sitting on their raised sieges, at each side of the grate. At one side of the base the door of the vault is shewn, and its course is marked by the dotted lines.

Detailed description of the crown-glass furnace, figs. 507. 508.--It is an oblong square, built in the centre of a brick cone, large enough to contain within it, two or three pots at each side of the grate room, which is either divided as shown in the plan, or runs the whole length of the furnace, as the manufacturer chooses. Fig. 507. is a ground plan, and fig. 508. a front elevation, of a six-pot furnace. 1, 2, 3, fig. 507., are the working holes for the purposes of ventilation, of putting in the materials, and of taking out the metal to be wrought. 4, 5, 6, 7, are pipe holes for warming the pipes before beginning to work with them. 8, 9, 10, are foot holes for mending the pots and sieges. 11 is a bar of iron for binding the furnace, and keeping it from swelling.

The arch is of an elliptic form; though a barrel arch, that is, an arch shaped like the half of a barrel cut longwise through the centre, is sometimes used. But this soon gives way when used in the manufacture of crown glass, although it does very well in the clay-furnace used for bottle houses.

The best stone for building furnaces is fire-stone, from Coxgreen in the neighbourhood of Newcastle. Its quality is a close grit, and it contains a greater quantity of talc than the common fire-stone, which seems to be the chief reason of its resisting the fire better. The great danger in building furnaces is, lest the cement at the top should give way with the excessive heat, and by dropping into the pots, spoil the metal. The top should therefore be built with stones only, as loose as they can hold together after the centres are removed, and without any cement whatever. The stones expand and come quite close together when annealing; an operation which takes from eight to fourteen days at most. There is thus less risk of any thing dropping from the roof of the furnace.

The inside of the square of the furnace is built either of Stourbridge fire-clay annealed, or the Newcastle fire-stone, to the thickness of sixteen inches. The outside is built of common brick about nine inches in thickness.

The furnace is thrown over an ash-pit, or cave as it is called, which admits the atmospheric air, and promotes the combustion of the furnace. This cave is built of stone until it comes beneath the grate room, when it is formed of fire-brick. The abutments are useful for binding and keeping the furnace together, and are built of masonry. The furnaces are stoutly clasped with iron all round, to keep them tight. In four-pot furnaces this is unnecessary, provided there be four good abutments.

Fig. 509. is an elevation of the flashing furnace. The outside is built of common brick, the inside of fire-brick, and the mouth or nose of Stourbridge fire-clay.

Fig. 510. is the annealing kiln. It is built of common brick, except round the grate room, where fire-brick is used.

Few tools are needed for blowing and flashing crown-glass. The requisite ball of plastic glass is gathered, in successive layers as for bottles, on the end of an iron tube, and rolled into a pear-shape, on a cast-iron plate; the workman taking care that the air blown into its cavity is surrounded with an equal body of glass, and if he perceives any side to be thicker than another, he corrects the inequality by rolling it on the sloping iron table called marver, (marbre). He now heats the bulb in the fire, and rolls it so as to form the glass upon the end of the tube, and by a dexterous swing or two he lengthens it, as shewn in I, fig. 511. To extend the neck of that pear, he next rolls it over a smooth iron rod, turned round in a horizontal direction, into the shape K, fig. 511. By further expansion at the blowing-furnace, he now brings it to the shape L, represented in fig. 511.

This spheroid having become cool and somewhat stiff, is next carried to the bottoming hole (like fig. 509.), to be exposed to the action of flame. A slight wall erected before one half of this hole, screens the workman from the heat, but leaves room for the globe to pass between it and the posterior wall. The blowing-pipe is made to rest a little way from the neck of the globe, on a hook fixed in the front wall; and thus may be made easily to revolve on its axis, and by giving centrifugal force to the globe, while the bottom of it, or part opposite to the pipe, is softened by the heat, it soon assumes the form exhibited in M, fig. 511.

In this state the flattened globe is removed from the fire, and its rod being rested on the casher box covered with coal cinders, another workman now applies the end of a solid iron rod tipped with melted glass, called a punto, to the nipple or prominence in the middle; and thus attaches it to the centre of the globe, while the first workman cracks off the globe by touching its tubular neck with an iron chisel dipped in cold water. The workman having thereby taken possession of the globe by its bottom or knobbed pole attached to his punty rod, he now carries it to another circular opening, where he exposes it to the action of moderate flame with regular rotation, and thus slowly heats the thick projecting remains of the former neck, and opens it slightly out, as shewn at N, in fig. 511. He next hands it to the flasher, who resting the iron rod in a hook placed near the side of the orifice A, fig. 509., wheels it rapidly round opposite to a powerful flame, till it assumes first the figure O, and finally that of a flat circular table.

The flasher then walks off with the table, keeping up a slight rotation as he moves along, and when it is sufficiently cool, he turns down his rod into a vertical position, and lays the table flat on a dry block of fire-clay, or bed of sand, when an assistant nips it off from the punto with a pair of long iron shears, or cracks it off with a touch of cold iron. The loose table or plate is lastly lifted up horizontally on a double pronged iron fork, introduced into the annealing arch fig. 510. and raised on edge; an assistant with a long-kneed fork preventing it from falling too rapidly backwards. In this arch a great many tables of glass are piled up in iron frames, and slowly cooled from a heat of about 600° to 100° F., which takes about 24 hours; when they are removed. A circular plate or table of about 5 feet diameter weighs on an average 9 pounds.

4. Flint glass.--This kind of glass is so called because originally made with calcined flints, as the siliceous ingredient. The materials at present employed in this country for the finest flint glass or crystal, are first, Lynn sand, calcined, sifted, and washed; second, an oxide of lead, either red lead or litharge; and third, pearl ash. The pearl ash of commerce must however be purified by digesting it in a very little hot water, which dissolves the carbonate of potash, and leaves the foreign salts, chiefly sulphate of potash, muriate of potash, and muriate of soda. The solution of the carbonate being allowed to cool and become clear in lead pans, is then run off into a shallow iron boiler, and evaporated to dryness. Nitre is generally added as a fourth ingredient of the body of the glass; and it serves to correct any imperfections which might arise from accidental combustible particles, or from the lead being not duly oxidized. The above four substances constitute the main articles; to which we may add arsenic and manganese, introduced in very small quantities, to purify the colour and clear up the transparency of the glass. The black oxide of manganese, when used in such quantity only as to peroxidize the iron of the sand, simply removes the green tinge caused by the iron; but if more manganese be added than accomplishes that purpose, it will give a purple tinge to the glass; and in fact, most manufacturers prefer to have an excess rather than a defect of manganese, since cut glass has its brilliancy increased by a faint lilac hue. The arsenic is supposed to counteract the injury arising from excess of manganese, but is itself very apt on the other hand to communicate some degree of opalescence, or at least, to impair the lustre of the glass. When too much manganese has been added, the purple tinge may indeed be removed by any carbonaceous matter, as by thrusting a wooden rod down into the liquid glass; but this cannot be done with good effect in practice, since the final purple tinge is not decided till the glass is perfectly formed, and then the introduction of charcoal would destroy the uniformity of the whole contents of the pot.

The raw materials of flint glass, are always mixed with about a third or a fourth of their weight of broken crystal of like quality; this mixture is thrown into the pot with a shovel; and more is added whenever the preceding portions by melting subside; the object being to obtain a pot full of glass, to facilitate the skimming off the impurities, and sandiver. The mouth of the pot is now shut, by applying clay-lute round the stopper, with the exception of a small orifice below, for the escape of the liquid saline matter. Flint glass requires about 48 hours for its complete vitrification, though the materials be more fusible than those of crown glass; in consequence of the contents of the pot being partially screened by its cover from the action of the fire, as also from the lower intensity of the heat.

Fig. 512. represents a flint glass house for 6 pots, with the arch or leer on one side for annealing the crystal ware. In fig. 513., the base of the cone is seen, and the glass pots in situ on their platform ranged round the central fire grate. The dotted line denotes the contour of the furnace, fig. 512.

Whenever the glass appears fine, and is freed from its air bubbles, which it usually is in about 36 hours, the heat is suffered to fall a little by closing the bottom valves, &c., that the pot may settle; but prior to working the metal, the heat is somewhat raised again.

It would be useless to describe the manual operations of fashioning the various articles of the flint-glass manufacture, because they are indefinitely varied to suit the conveniences and caprices of human society.

Every different flint-house has a peculiar proportion of glass materials. The following have been offered as good practical mixtures.

1. Fine white sand 300 parts. Red lead or litharge 200 Refined pearl ashes 80 Nitre 20 Arsenic and manganese, a minute quantity.

In my opinion, the proportion of lead is too great in the above recipe, which is given on the authority of Mr. James Geddes, of Leith. The glass made with it would be probably yellowish, and dull.

2. Fine sand 50·5 Litharge 27·2 Refined pearl ashes (carbonate of potash, with 5 per cent. of water) 17·5 Nitre 4·8 ----- 100·0

To these quantities from 30 to 50 parts of broken glass or cullet are added; with about a two-thousandth part of manganese, and a three-thousandth part of arsenic. But manganese varies so extremely in its purity, and contains often so much oxide of iron, that nothing can be predicated as to its quantity previously to trial.

M. Payen, an eminent manufacturing chemist in France, says that the composition of crystal does not deviate much from the following proportions:--

Wood fire. Coal fire. Siliceous sand 3 3 Minium 2 2-1/4 Carbonate of potash 1-1/2 1-2/3

I conceive that this glass contains too much lead and potash. Such a mixture will produce a dull metal, very attractive of moisture: defects to which the French crown-glass also is subject.

The flint-glass leer for annealing glass, is an arched gallery or large flue, about 36 feet long, 3 feet high, 4 wide; having its floor raised above 2 feet above the ground of the glass-house. The hot air and smoke of a fire-place at one end pass along this gallery, and are discharged by a chimney 8 or 10 feet short of the other end. On the floor of the vault, large iron trays are laid and hooked to each other in a series, which are drawn from the fire end towards the other by a chain, wound about a cylinder by a winch-handle projecting through the side. The flint-glass articles are placed in their hot state into the tray next the fire, which is moved onwards to a cooler station whenever it is filled, and an empty tray is set in its place. Thus, in the course of about 20 hours, the glass advances to the cool end thoroughly annealed.

Besides colourless transparent glass, which forms the most important part of this manufacture, various coloured glasses are made to suit the taste of the public. The taste at Paris was lately for opaline crystal; which may be prepared by adding to the above composition (No. 2.) phosphate of lime, or well burnt bone-ash in fine powder, washed, and dried. The article must be as uniform in thickness as possible, and speedily worked into shape, with a moderate heat. Oxide of tin, putty, was formerly used for making opalescent glass, but the lustre of the body was always impaired by its means.

Crystal vessels have been made recently of which the inner surface is colourless, and all the external facets coloured. Such works are easily executed. The end of the blowing-rod must be dipped first in the pot containing colourless glass, to form a bulb of a certain size, which being cooled a little is then dipped for an instant into the pot of coloured glass. The two layers are associated without intermixture; and when the article is finished in its form, it is white within and coloured without. Fluted lines somewhat deeply cut, pass through the coloured coat, and enter the colourless one; so that when they cross, their ends alone are coloured.

For some time past, likewise, various crystal articles have been exhibited in the market with coloured enamel-figures on their surface, or with white incrustations of a silvery lustre in their interior. The former are prepared by placing the enamel object in the brass mould, at the place where it is sought to be attached. The bulb of glass being put into the mould, and blown while very hot, the small plate of enamel gets cemented to the surface. For making the white argentine incrustations, small figures are prepared with an impalpable powder of dry porcelain paste, cemented into a solid by means of a little gypsum plaster. When these pieces are thoroughly dried, they are laid on the glass while it is red hot, and a large patch of very liquid glass is placed above it, so as to encase it and form one body with the whole. In this way the incrustation is completely enclosed; and the polished surface of the crystal which scarcely touches it, gives a brilliant aspect, pleasing to the eye.

An uniform flint-glass, free from striæ, or wreath, is much in demand for the optician. It would appear that such an article was much more commonly made by the English manufacturers many years ago, than at present; and that in improving the brilliancy of crystal-glass they have injured its fitness for constructing optical lenses, which depends not so much on its whiteness and lustre as on the layers of different densities being parallel to each other. The oxide of lead existing in certain parts of a potful of glass in greater proportion than in other parts, increases the density unequally in the same mass, so that the adjoining strata are often very different in this respect. Even a potful of pretty uniform glass, when it stands some time liquid, becomes eventually unequable by the subsidence of the denser portions; so that striæ and gelatinous appearances begin to manifest themselves, and the glass becomes of little value. Glass allowed to cool slowly in mass in the pot is particularly full of wreath; and if quickly refrigerated, that is in two or three hours, it is apt to split into a multitude of minute splinters, of which no use can be made. For optical purposes, the glass must be taken out in its liquid state, being gathered on the end of the iron rod from the central portion of a recently skimmed pot, after the upper layers have been worked off in general articles.

M. Guinand, of Brennets near Geneva, appears to have hit upon processes that furnished almost certainly pieces of flint-glass capable of forming good lenses of remarkable dimensions, even of 11 inches diameter; of adequate density and transparency, and nearly free from striæ. M. Cauchoix, the eminent French optician, says, that out of ten object glasses, 4 inches in diameter, made with M. Guinand’s flint-glass, eight or nine turned out very good, while out of an equal number of object glasses made of the flint-glass of the English and French manufactories, only one, or two at most, were found serviceable. The means by which M. Guinand arrived at these results have not been published. He has lately died, and it is not known whether his son be in possession of his secret.

An achromatic object glass for telescopes and microscopes consists of at least two lenses; the one made with glass of lead, or flint glass, and the other with crown glass; the former possessing a power of dispersing the coloured rays relatively to its mean refractive power, much greater than the latter; upon which principle, the achromatism of the image is produced, by re-uniting the different coloured rays into one focus. Flint glass to be fit for this delicate purpose must be perfectly homogeneous, or of uniform density throughout its substance, and free from wavy veins or wreathes; for every such inequality would occasion a corresponding inequality in the refraction and dispersion of the light; like what is perceived in looking through a thick and thin solution of gum Arabic imperfectly mixed. Three plans have been prescribed for obtaining homogeneous pieces of optical glass: 1. to lift a mass of it in large ladles, and let it cool in them; 2. to pour it out from the pots into moulds; 3. to allow it to cool in the pots, and afterwards to cut it off in horizontal strata. The last method, which is the most plausible, seldom affords pieces of uniform density, unless peculiar precautions have been adopted to settle the flint glass in uniform strata; because its materials are of such unequal density, the oxide of lead having a specific gravity of 8, and silica of 2·7, that they are apt to stand at irregular heights in the pots.

One main cause of these inequalities lies in the construction of the furnace, whereby the bottom of the pot is usually much less heated than the upper part. In a plate glass furnace the temperature of the top of the pot has been found to be 130° Wedgew., while that of the bottom was only 110°, constituting a difference of no less than 2610° F. The necessary consequence is that the denser particles which subside to the bottom, during the fusion of the materials, and after the first extrication of the gases, must remain there, not being duly agitated by the expansive force of caloric, acting from below upwards.

The preparation of the best optical glass is now made a great mystery by one or two proficients. The following suggestions, deduced from a consideration of principles, may probably lead to some improvements, if judiciously applied. The great object is to counteract the tendency of the glass of lead to distribute itself into strata of different densities; which may be effected either by mechanical agitation or by applying the greatest heat to the bottom of the pot. But however homogeneous the glass may be thereby made, its subsequent separation into strata of different densities must be prevented by rapid cooling and solidification. As the deeper the pots, the greater is the chance of unequal specific gravity in their contents, it would be advisable to make them wider and shallower than those in use for making ordinary glass. The intermixture may be effected either by lading the glass out of one pot into another in the furnace, and back again, with copper ladles, or by stirring it up with a rouser, then allowing it to settle for a short time, till it becomes clear and free from air bubbles. The pot may now be removed from the furnace, in order to solidify its contents in their homogeneous state; after which the glass may be broken in pieces, and be perfected by subjecting it to a second fusion; or what is easier and quicker, we may form suitable discs of glass without breaking down the potful, by lifting it out in flat copper ladles with iron shanks, and transferring the lumps after a little while into the annealing leer.

To render a potful of glass homogeneous by agitation, is a more difficult task, as an iron rod would discolour it, and a copper rod would be apt to melt. An iron rod sheathed in laminated platinum would answer well, but for its expense. A stone-ware tube supported within by a rod of iron, might also be employed for the purpose in careful hands; the stirring being repeated several times, till at last the glass is suffered to stiffen a little by decrease of temperature. It must be then allowed to settle and cool, after which the pot, being of small dimensions, may be drawn out of the fire.

2. The second method of producing the desired uniformity of mixture, consists in applying a greater heat to the bottom than to the upper part of the melting pot. Fig. 514. represents in section a furnace contrived to effect this object. It is cylindrical, and of a diameter no greater than to allow the flames to play round the pot, containing from three to four cwts. of vitreous materials. A is the pot, resting upon the arched grid b a, built of fire-bricks, whose apertures are wide enough to let the flames rise freely, and strike the bottom and sides of the vessel. From 1-1/2 to 2 feet under that arch, the fuel grate c d is placed. B C are the two working openings for introducing the materials, and inspecting the progress of the fusion; they must be closed with fire-tiles and luted with fire-clay at the beginning of the process. At the back of the furnace, opposite the mouth of the fire-place, there is a door-way, which is bricked up, except upon occasion of putting in and taking out the pot. The draught is regulated by means of a slide-plate upon the mouth of the ash-pit f. The pot being heated to the proper pitch, some purified pearl ash, mixed with fully twice its weight of colourless quartz sand, is to be thrown into it, and after the complete fusion of this mixture, the remaining part of the sand along with the oxide of lead (fine litharge) is to be strown upon the surface. These siliceous particles in their descent serve to extricate the air from the mass. Whenever the whole is fused, the heat must be strongly urged to ensure a complete uniformity of combination by the internal motions of the particles. As soon as the glass has been found by making test phials to be perfectly fine, the fire must be withdrawn, the two working holes must be opened, as well as the mouths of the fire-place and ash-pit, to admit free ingress to cooling currents of air, so as to congeal the liquid mass as quickly as possible; a condition essential to the uniformity of the glass. It may be worth while to stir it a little with the pottery rod at the commencement of the cooling process. The solidified glass may be afterwards detached by a hammer in conchoidal discs, which after chipping off their edges, are to be placed in proper porcelain or stone-ware dishes, and exposed to a softening heat, in order to give them a lenticular shape. Great care must be taken that the heat thus applied by the muffle furnace be very equable, for otherwise wreathes might be very readily re-produced in the discs. A small oven upon the plan of a baker’s, is best fitted for this purpose, which being heated to dull redness, and then extinguished, is ready to soften and afterwards anneal the conchoidal pieces.

Guinand’s dense optical flint glass, of specific gravity 3·616, consists by analysis, of oxide of lead 43·05; silica 44·3; and potash 11·75; but requires for its formation the following ingredients: 100 pounds of ground quartz; 100 pounds of fine red lead; 35 pounds of purified potash; and from 2 to 4 pounds of saltpetre. As this species of glass is injured by an excess of potash, it should be compounded with rather a defect of it, and melted by a proportionally higher or longer heat. A good optical glass has been made in Germany with 7 parts of pure red lead, 3 parts of finely ground quartz, and 2 parts of calcined borax.

5. Plate glass.

This, like English crown-glass, has a soda flux, whereas flint-glass requires potash, and is never of good quality when made with soda. We shall distribute our account of this manufacture under two heads.

1. The different furnaces and principal machines, without whose knowledge it would be impossible to understand the several processes of a plate-glass factory.

2. The materials which enter into the composition of this kind of glass, and the series of operations which they undergo; devoting our chief attention to the changes and improvements which long experience, enlightened by modern chemistry, has introduced into the great manufactory of Saint-Gobin in France, under the direction of M. Tassaert. It may however be remarked that the English plate-glass manufacture derives peculiar advantages from the excellence of its grinding and polishing machinery.

The clay for making the bricks and pots should be free from lime and iron, and very refractory. It is mixed with the powder of old pots passed through a silk sieve. If the clay be very plastic it will bear its own weight of the powder, but if shorter in quality, it will take only three-fifths. But before mingling it with the cement of old pots, it must be dried, bruised, then picked, ground, and finally elutriated by agitation with water, decantation through a hair sieve, and subsidence. The clay fluid after passing the sieve is called slip (coulis.)

The furnace is built of dry bricks, cemented with slip, and has at each of its four angles a peculiar annealing arch, which communicates with the furnace interiorly, and thence derives sufficient heat to effect in part, if not wholly, the annealing of the pots, which are always deposited there a long time before they are used. Three of these arches exclusively appropriated to this purpose, are called pot-arches. The fourth is called the arch of the materials, because it serves for drying them before they are founded. Each arch has, moreover, a principal opening called the throat, another called bonnard, by the French workmen, through which fire may be kindled in the arch itself, when it was thought to be necessary for the annealing of the pots; a practice now abandoned. The duration of a furnace is commonly a year, or at most 14 months; that of the arches is 30 years or upwards, as they are not exposed to so strong a heat.

In the manufacture of plate-glass two sorts of crucibles are employed, called the pots and the basins, (cuvettes). The first serve for containing the materials to be founded, and for keeping them a long time in the melted state. The cuvettes receive the melted glass after it is refined, and decant it out on the table to be rolled into a plate. Three pots hold liquid glass for six small basins, or for three large ones, the latter being employed for making mirrors of great dimensions, that is, 100 inches long and upwards. Furnaces have been lately constructed with 6 pots, and 12 cuvettes, 8 of which are small, and 4 large; and cuvettes of three sizes are made, called small, middling, and large. The small are perfect cubes, the middling and the large ones are oblong parallelopipeds. Towards the middle of their height, a notch or groove, two or three inches broad, and an inch deep, is left, called the girdle of the cuvette, by which part they are grasped with the tongs, or rather are clamped in the iron frame. This frame goes round the four sides of the small cuvettes, and may be placed indifferently upon all their sides; in the other cuvettes, the girdle extends only over the two large sides, because they cannot be turned up. See m T, fig. 515., p. 590.

The pot is an inverted truncated cone, like a crown glass pot. It is about 30 inches high, and from 30 to 32 inches wide, including its thickness. There is only a few inches of difference between the diameter of the top and that of the bottom. The bottom is 3 inches thick, and the body turns gradually thinner till it is an inch at the mouth of the pot.

The large building or factory, of which the melting furnace occupies the middle space, is called the halle in French. At Ravenhead in Lancashire it is called the foundry, and is of magnificent dimensions, being probably the largest apartment under one roof in Great Britain, since its length is 339 feet, and its breadth 155. The famous halle of St. Gobin is 174 feet by 120. Along the two side walls of the halle, which are solidly constructed of hewn stone, there are openings like those of common ovens. These ovens, destined for the annealing of the newly cast plates, bear the name of carquaises. Their soles are raised two feet and a half above the level of the ground, in order to bring them into the same horizontal plane with the casting tables. Their length, amounting sometimes to 30 feet, and their breadth to 20, are required in order to accommodate 6, 8, or even 10 plates of glass, alongside of each other. The front aperture is called the throat, and the back door the little throat (gueulette). The carquaise is heated by means of a fire-place of a square form called a tisar, which extends along its side.

The founding or melting furnace is a square brick building laid on solid foundations, being from 8 to 10 feet in each of its fronts, and rising inside into a vault or crown about 10 feet high. At each angle of this square, a small oven or arch is constructed, likewise vaulted within, and communicating with the melting furnace by square flues, called lunettes, through which it receives a powerful heat, though much inferior to that round the pots. The arches are so distributed as that two of the exterior sides of the furnace stand wholly free, while the two other sides, on which the arches encroach, offer a free space of only 3 feet. In this interjacent space, two principal openings of the furnace, of equal size in each side, are left in the building. These are called tunnels. They are destined for the introduction of the pots and the fuel.

On looking through the tunnels into the inside of the furnace, we perceive to the right hand and the left, along the two free sides, two low platforms or sieges, at least 30 inches in height and breadth. See figs. 506. 508.

These sieges (seats) being intended to support the pots and the cuvettes filled with heavy materials, are terminated by a slope, which ensures the solidity of the fire-clay mound. The slopes of the two sieges extend towards the middle of the furnace so near as to leave a space of only from 6 to 10 inches between them for the hearth. The end of this is perforated with a hole sufficiently large to give passage to the liquid glass of a broken pot, while the rest is preserved by lading it from the mouth into the adjoining cuvette.

In the two large parallel sides of the furnace, other apertures are left much smaller than the tunnels, which are called ouvreaux (peep holes). The lower ones, or the ouvreaux en bas, called cuvette openings, because being allotted to the admission of these vessels, they are exactly on a level with the surface of the sieges, and with the floor of the halle. Plates of cast iron form the thresholds of these openings, and facilitate the ingress and egress of the cuvettes. The apertures are arched at top, with hewn stone like the tunnels, and are 18 inches wide when the cuvettes are 16 inches broad.

The upper and smaller apertures, or the higher ouvreaux called the lading holes, because they serve for transvasing the liquid glass, are three in number, and are placed 31 or 32 inches above the surface of the sieges. As the pots are only 30 inches high, it becomes easy to work through these openings either in the pots or the cuvettes. The pots stand opposite to the two pillars which separate the openings, so that a space is left between them for one or more cuvettes according to the size of the latter. It is obvious that if the tunnels and ouvreaux were left open, the furnace would not draw or take the requisite founding heat. Hence the openings are shut by means of fire-tiles. These are put in their places, and removed by means of two holes left in them, in correspondence with the two prongs of a large iron fork supported by an axle and two iron wheels, and terminated by two handles which the workmen lay hold of when they wish to move the tile.

The closing of the tunnel is more complex. When it is shut or ready for the firing, the aperture appears built up with bricks and mortar from the top of the arch to the middle of the tunnel. The remainder of the door-way is closed; 1. on the two sides down to the bottom, by a small upright wall, likewise of bricks, and 8 inches broad, called walls of the glaye; 2. by an assemblage of pieces called pieces of the glaye, because the whole of the closure of the tunnel bears the name of glaye. The upper hole, 4 inches square, is called the tisar, through which billets of wood are tossed into the fire. Fuel is also introduced into the posterior openings. The fire is always kept up on the hearth of the tunnel, which is, on this account, 4 inches higher than the furnace-hearth, in order that the glass which may accidentally fall down on it, and which does not flow off by the bottom hole, may not impede the combustion. Should a body of glass, however, at any time obstruct the grate, it must be removed with rakes, by opening the tunnel and dismounting the fire-tile stoppers of the glaye.

Formerly wood fuel alone was employed for heating the melting-furnaces of the mirror-plate manufactory of Saint-Gobin; but within these few years, the Director of the works makes use with nearly equal advantage of pit-coal. In the same establishment, two melting furnaces may be seen, one of which is fixed with wood, and the other with coals, without any difference being perceptible in the quality of the glass furnished by either. It is not true, as has been stated, that the introduction of pit-coal has made it necessary to work with covered pots in order to avoid the discoloration of the materials, or that more alkali was required to compensate for the diminished heat in the covered pots. They are not now covered when pit-coal is used, and the same success is obtained as heretofore by leaving the materials two or three hours longer in the pots and the cuvettes. The construction of the furnaces in which coal is burned, is the same as that with wood, with slight modifications. Instead of the close bottomed hearth of the wood furnace, there is an iron grate in the coal-hearth through which the air enters, and the waste ashes descend.

When billets of wood were used as fuel, they were well dried beforehand, by being placed a few days on a frame work of wood called the wheel, placed two feet above the furnace and its arches, and supported on four pillars at some distance from the angles of the building.

Composition of plate-glass.--This is not made now, as formerly, by random trials. The progress of chemistry, the discovery of a good process for the manufacture of soda from sea salt, which furnishes a pure alkali of uniform power, and the certain methods of ascertaining its purity, have rendered this department of glass-making almost entirely new, in France. At Saint-Gobin no alkali is employed at present except artificial crystals of soda, prepared at the manufactory of Chauny, subsidiary to that establishment. Leaden chambers are also erected there for the production of sulphuric acid from sulphur. The first crop of soda crystals is reserved for the plate-glass manufacture, the other crystals and the mother-water salts are sold to the makers of inferior glass.

At the mirror-plate works of Ravenhead, near St. Helen’s in Lancashire, soda crystals, from the decomposition of the sulphate of soda by chalk and coal, have been also tried, but without equal success as at Saint-Gobin; the failure being unquestionably due to the impurity of the alkali. Hence, in the English establishment the soda is obtained by treating sea-salt with pearl-ash, whence carbonate of soda and muriate of potash result. The latter salt is crystallized out of the mingled solution, by evaporation at a moderate heat, for the carbonate of soda does not readily crystallize till the temperature of the solution fall below 60° Fahr. When the muriate of potash is thus removed, the alkaline carbonate is evaporated to dryness.

Long experience at Saint-Gobin has proved that one part of dry carbonate of soda is adequate to vitrify perfectly three parts of fine siliceous sand, as that of the mound of Aumont near Senlis, of Alum Bay in the Isle of Wight, or of Lynn in Norfolk. It is also known that the degree of heat has a great influence upon the vitrification, and that increase of temperature will compensate for a certain deficiency of alkali; for it is certain that a very strong fire always dissipates a good deal of the soda, and yet the glass is not less beautiful. The most perfect mirror-plate has constantly afforded to M. Vauquelin in analysis, a portion of soda inferior to what had been employed in its formation. Hence, it has become the practice to add for every 100 parts of cullet or broken plate that is mixed with the glass composition, one part of alkali, to make up for the loss that the old glass must have experienced.

To the above mentioned proportions of sand and alkali independently of the cullet which may be used, dry slaked lime carefully sifted is to be added to the amount of one seventh of the sand; or the proportion will be, sand 7 cwt.; quicklime 1 cwt.; dry carbonate of soda 2 cwt. and 37 lbs.; besides cullet. The lime improves the quality of the glass, rendering it less brittle and less liable to change. The preceding quantities of materials suitably blended, have been uniformly found to afford most advantageous results. The practice formerly was to dry that mixture, as soon as it was made, in the arch for the materials, but it has been ascertained that this step may be dispensed with, and the small portion of humidity present is dissipated almost instantly after they are thrown into the furnace. The coat of glaze previously applied to the inside of the pot, prevents the moisture from doing them any harm. For this reason, when the demand for glass at Saint-Gobin is very great, the materials are neither fritted nor even dried, but shovelled directly into the pot; this is called founding raw. Six workmen are employed in shovelling-in the materials either fritted or otherwise, for the sake of expedition, and to prevent the furnace getting cooled. One-third of the mixture is introduced at first; whenever this is melted, the second third is thrown in, and then the last. These three stages are called the first, second, and third fusion or founding.

According to the ancient practice, the founding and refining were both executed in the pots, and it was not till the glass was refined, that it was laded into the cuvettes, where it remained only 3 hours, the time necessary for the disengagement of the air bubbles introduced by the transvasion, and for giving the metal the proper consistence for casting. At present, the period requisite for founding and refining, is equally divided between the pots and the cuvettes. The materials are left 16 hours in the pots, and as many in the cuvettes; so that in 32 hours, the glass is ready to be cast. During the last two or three hours, the fireman or tiseur ceases to add fuel; all the openings are shut, and the glass is allowed to assume the requisite fluidity; an operation called stopping the glass, or performing the ceremony.

The transfer of the glass into the cuvettes, is called lading, (tréjetage). Before this is done, the cuvettes are cleared out, that is, the glass remaining on their bottom, is removed, and the ashes of the firing. They are lifted red hot out of the furnace by the method presently to be described, and placed on an iron plate, near a tub filled with water. The workmen, by means of iron paddles 6 feet long, flattened at one end and hammered to an edge, scoop out the fluid glass expeditiously, and throw it into water; the cuvettes are now returned to the furnace, and a few minutes afterwards the lading begins.

In this operation, ladles of wrought iron are employed, furnished with long handles, which are plunged into the pots through the upper openings or lading holes, and immediately transfer their charge of glass into the buckets. Each workman dips his ladle only three times, and empties its contents into the cuvette. By these three immersions (whence the term tréjeter is derived), the large iron spoon is heated so much that when plunged into a tub full of water, it makes a noise like the roaring of a lion, which may be heard to a very great distance.

The founding, refining, and ceremony, being finished, they next try whether the glass be ready for casting. With this view, the end of a rod is dipped into the bucket, which is called drawing the glass, the portion taken up being allowed to run off, naturally assumes a pear-shape, from the appearance of which, they can judge if the consistence be proper, and if any air bubbles remain. If all be right, the cuvettes are taken out of the furnace, and conveyed to the part of the halle where their contents are to be poured out. This process requires peculiar instruments and manipulations.

Casting.--While the glass is refining, that is, coming to its highest point of perfection, preparation is made for the most important process, the casting of the plate, whose success crowns all the preliminary labours and cares. The oven or carquaise destined to receive and anneal the plate, is now heated by its small fire or tisar, to such a pitch that its sole may have the same temperature as that of the plates, being nearly red-hot at the moment of their being introduced. An unequal degree of heat in the carquaise would cause breakage of the glass. The casting table is then rolled towards the front door or throat, by means of levers, and its surface is brought exactly to the level of the sole of the oven.

The table T, fig. 515., is a mass of bronze, or now preferably cast-iron, about 10 feet long, 5 feet broad, and from 6 to 7 inches thick, supported by a frame of carpentry, which rests on three cast-iron wheels. At the end of the table opposite to that next to the front of the oven, is a very strong frame of timber-work, called the puppet or standard, upon which the bronze roller which spreads the glass is laid, before and after the casting. This is 5 feet long by 1 foot in diameter; it is thick in the metal but hollow in the axis. The same roller can serve only for two plates at one casting, when another is put in its place, and the first is laid aside to cool; for otherwise the hot roller would at a third casting, make the plate expand unequally, and cause it to crack. When the rollers are not in action, they are laid aside in strong wooden trestles, like those employed by sawyers. On the two sides of the table in the line of its length, are two parallel bars of bronze, t, t, destined to support the roller during its passage from end to end; the thickness of these bars determines that of the plate. The table being thus arranged, a crane is had recourse to for lifting the cuvette, and keeping it suspended, till it be emptied upon the table. This raising and suspension are effected by means of an iron gib, furnished with pullies, held horizontally, and which turns with them.

The tongs T, fig. 515., are made of four iron bars, bent into a square frame in their middle, for embracing the bucket. Four chains proceeding from the corners of the frame V, are united at their other ends into a ring which fits into the hook of the crane.

Things being thus arranged, all the workmen of the foundry co-operate in the manipulations of the casting. Two of them fetch, and place quickly in front of one of the lower openings, the small cuvette-carriage, which bears a forked bar of iron, having two prongs corresponding to the two holes left in the fire-tile door. This fork mounted on the axle of two cast-iron wheels, extends at its other end into two branches terminated by handles, by which the workmen move the fork, lift out the tile stopper, and set it down against the outer wall of the furnace.

The instant these men retire, two others push forward into the opening the extremity of the tongs-carriage, so as to seize the bucket by the girdle, or rather to clamp it. At the same time, a third workman is busy with an iron pinch or long chisel, detaching the bucket from its seat, to which it often adheres by some spilt glass; whenever it is free, he withdraws it from the furnace. Two powerful branches of iron united by a bolt, like two scissor blades, which open, come together, and join by a quadrant near the other end, form the tongs-carriage, which is mounted upon two wheels like a truck.

The same description will apply almost wholly to the iron-plate carriage, on which the bucket is laid the moment it is taken out of the furnace; the only difference in its construction is, that on the bent iron bars which form the tail or lower steps of this carriage (in place of the tongs) is permanently fastened an iron plate, on which the bucket is placed and carried for the casting.

Whenever the cuvette is set upon its carriage, it must be rapidly wheeled to its station near the crane. The tongs T above described are now applied to the girdle, and are then hooked upon the crane by the suspension chains. In this position the bucket is skimmed by means of a copper tool called a sabre, because it has nearly the shape of that weapon. Every portion of the matter removed by the sabre is thrown into a copper ladle (poche de gamin), which is emptied from time to time into a cistern of water. After being skimmed, the bucket is lifted up, and brushed very clean on its sides and bottom; then by the double handles of the suspension-tongs it is swung round to the table, where it is seized by the workmen appointed to turn it over; the roller having been previously laid on its ruler-bars, near the end of the table which is in contact with the annealing oven. The cuvette-men begin to pour out towards the right extremity E of the roller, and terminate when it has arrived at the left extremity D. While preparing to do so, and at the instant of casting, two men place within the ruler-bar on each side, that is between the bar and the liquid glass, two iron instruments called hands, m, m, m, m, which prevent the glass from spreading beyond the rulers, whilst another draws along the table the wiping bar c, c, wrapped in linen, to remove dust, or any small objects which may interpose between the table and the liquid glass.

Whenever the melted glass is poured out, two men spread it over the table, guiding the roller slowly and steadily along, beyond the limits of the glass, and then run it smartly into the wooden standard prepared for its reception, in place of the trestles V, V.

The empty bucket, while still red-hot, is hung again upon the crane, set on its plate-iron carriage, freed from its tongs, and replaced in the furnace, to be speedily cleared out anew, and charged with fresh fluid from the pots. If while the roller glides along, the two workmen who stand by with picking tools, perceive tears in the matter in advance of the roller, and can dexterously snatch them out, they are suitably rewarded, according to the spot where the blemish lay, whether in the centre, where it would have proved most detrimental, or near the edge. These tears proceed usually from small portions of semi-vitrified matter which fall from the vault of the furnace, and from their density occupy the bottom of the cuvettes.

While the plate is still red-hot and ductile, about 2 inches of its end opposite to the carquaise door is turned up with a tool; this portion is called the head of the mirror; against the outside of this head, the shovel, in the shape of a rake without teeth, is applied, with which the plate is eventually pushed into the oven, while two other workmen press upon the upper part of the head with a wooden pole, eight feet long, to preserve the plate in its horizontal position, and prevent its being warped. The plate is now left for a few moments near the throat of the carquaise, to give it solidity; after which it is pushed further in by means of a very long iron tool, whose extremity is forked like the letter y, and hence bears that name; and is thereby arranged in the most suitable spot for allowing other plates to be introduced.

However numerous the manipulations executed from the moment of withdrawing the cuvette from the furnace, till the cast-plate is pushed into the annealing oven, I have seen them all performed in less than five minutes; such silence, order, regularity, and despatch prevail in the establishment of Saint-Gobin.

When all the plates of the same casting have been placed in the carquaise, it is sealed up, that is to say, all its orifices are closed with sheets of iron, surrounded and made tight with plastic loam. With this precaution, the cooling goes on slowly and equably in every part, for no cooling current can have access to the interior of the oven.

After they are perfectly cooled, the plates are carefully withdrawn one after another, keeping them all the while in a horizontal position, till they are entirely out of the carquaise. As soon as each plate is taken out, one set of workmen lower quickly and steadily the edge which they hold, while another set raise the opposite edge, till the glass be placed upright on two cushions stuffed with straw, and covered with canvas. In this vertical position they pass through, beneath the lower edge of the plate, three girths or straps each four feet long, thickened with leather in their middle, and ending in wooden handles; so that one embraces the middle of the plate, and the other two, the ends. The workmen, six in number, now seize the handles of the straps, lift up the glass closely to their bodies, and convey it with a regular step to the warehouse. Here the head of the plate is first cut off with a diamond square, and then the whole is attentively examined, in reference to its defects and imperfections, to determine the sections which must be made of it, and the eventual size of the pieces. The pairings and small cuttings detached are set aside, in order to be ground and mixed with the raw materials of another glass-pot.

The apartment in which the roughing-down and smoothing of the plates is performed, is furnished with a considerable number of stone tables, truly hewn and placed apart like billiard tables, in a horizontal position, about 2 feet above the ground. They are rectangular, and of different sizes proportional to the dimensions of the plates, which they ought always to exceed a little. These tables are supported either on stone pillars or wooden frames, and are surrounded with a wooden board whose upper edge stands somewhat below their level, and leaves in the space between it and the stone all round an interval of 3 or 4 inches, of which we shall presently see the use.

A cast plate, unless formed on a table quite new, has always one of its faces, the one next the table, rougher than the other; and with this face the roughing-down begins. With this view, the smoother face is cemented on the stone table with Paris-plaster. But often instead of one plate, several are cemented alongside of each other, those of the same thickness being carefully selected. They then take one or more crude plates of about one-third or one-fourth the surface of the plate fixed to the table, and fix it on them with liquid gypsum to the large base of a quadrangular truncated pyramid of stone; of a weight proportioned to its extent, or about a pound to the square inch. This pyramidal muller, if small sized, bears at each of its angles of the upper face a peg or ball, which the grinders lay hold of in working it; but when of greater dimension, there is adapted to it horizontally a wheel of slight construction, 8 or 10 feet in diameter, whose circumference is made of wood rounded so as to be seized with the hand. The upper plate is now rubbed over the lower ones, with moistened sand applied between.

This operation is however performed by machinery. The under plate being fixed or imbedded in stucco, on a solid table, the upper one likewise imbedded by the same cement in a cast-iron frame, has a motion of circum-rotation given to it closely resembling that communicated by the human hand and arm, moist sand being supplied between them. While an excentric mechanism imparts this double rotatory movement to the upper plate round its own centre, and of that centre round a point in the lower plate, this plate placed on a moveable platform changes its position by a slow horizontal motion, both in the direction of its length and its breadth. By this ingenious contrivance, which pervades the whole of the grinding and polishing machinery, a remarkable regularity of friction and truth of surface is produced. When the plates are sufficiently worked on one face, they are reversed in the frames, and worked together on the other. The Paris plaster is usually coloured red, in order to shew any defects in the glass.

The smoothing of the plates is effected on the same principles by the use of moist emery washed to successive degrees of fineness, for the successive stages of the operation; and the polishing process is performed by rubbers of hat-felt and a thin paste of colcothar and water. The colcothar, called also crocus, is red oxide of iron prepared by the ignition of copperas, with grinding and elutriation of the residuum.

The last part of the polishing process is performed by hand. This is managed by females, who slide one plate over another, while a little moistened putty of tin finely levigated is thrown between.

Large mirror-plates are now the indispensable ornaments of every large and sumptuous apartment; they diffuse lustre and gaiety round them, by reflecting the rays of light in a thousand lines, and by multiplying indefinitely the images of objects placed between opposite parallel planes.

The silvering of plane mirrors consists in applying a layer of tin-foil alloyed with mercury to their posterior surface. The workshop for executing this operation is provided with a great many smooth tables of fine freestone or marble, truly levelled, having round their contour a rising ledge, within which there is a gutter or groove which terminates by a slight slope in a spout at one of the corners. These tables rest upon an axis of wood or iron which runs along the middle of their length; so that they may be inclined easily into an angle with the horizon of 12 or 13 degrees, by means of a hand-screw fixed below. They are also furnished with brushes, with glass rules, with rolls of woollen stuff, several pieces of flannel, and a great many weights of stone or cast-iron.

The glass-tinner, standing towards one angle of his table, sweeps and wipes its surface with the greatest care, along the whole surface to be occupied by the mirror-plate; then taking a sheet of tin-foil adapted to his purpose, he spreads it on the table, and applies it closely with a brush, which removes any folds or wrinkles. The table being horizontal, he pours over the tin a small quantity of quicksilver, and spreads it with a roll of woollen stuff; so that the tin-foil is penetrated and apparently dissolved by the mercury. Placing now two rules, to the right and to the left, on the borders of the sheet, he pours on the middle a quantity of mercury sufficient to form every where a layer about the thickness of a crown piece; then removing with a linen rag the oxide or other impurities, he applies to it the edge of a sheet of paper, and advances it about half an inch. Meanwhile another workman is occupied in drying very nicely the surface of the glass that is to be silvered, and then hands it to the master workman, who, laying it flat, places its anterior edge first on the table, and then on the slip of paper; now pushing the glass forwards, he takes care to slide it along so that neither air nor any coat of oxide on the mercury can remain beneath the plate. When this has reached its position, he fixes it there by a weight applied on its side, and gives the table a gentle slope, to run off all the loose quicksilver by the gutter and spout. At the end of five minutes he covers the mirror with a piece of flannel, and loads it with a great many weights, which are left upon it for 24 hours, under a gradually increased inclination of the table. By this time the plate is ready to be taken off the marble table, and laid on a wooden one sloped like a reading desk, with its under edge resting on the ground, while the upper is raised successively to different elevations by means of a cord passing over a pulley in the ceiling of the room. Thus the mirror has its slope graduated from day to day, till it finally arrives at a vertical position. About a month is required for draining out the superfluous mercury from large mirrors; and from 18 to 20 days from those of moderate size. The sheets of tin-foil being always somewhat larger than the glass-plate, their edges must be pared smooth off, before the plate is lifted off the marble table.

Process for silvering concave mirrors.--Having prepared some very fine Paris plaster by passing it through a silk sieve, and some a little coarser passed through hair-cloth, the first is to be made into a creamy liquor with water, and after smearing the concave surface of the glass with a film of olive oil, the fine plaster is to be poured into it, and spread by turning about, till a layer of plaster be formed about a tenth of an inch thick. The second or coarse plaster, being now made into a thin paste, poured over the first, and moved about, readily incorporates with it, in its imperfectly hardened state. Thus an exact mould is obtained of the concave surface of the glass, which lies about three-quarters of an inch thick upon it, but is not allowed to rise above its outer edge.

The mould being perfectly dried, must be marked with a point of coincidence on the glass, in order to permit of its being exactly replaced in the same position, after it has been lifted out. The mould is now removed, and a round sheet of tin-foil is applied to it, so large that an inch of its edge may project beyond the plaster all round; this border being necessary for fixing the tin to the contour of the mould by pellets of white wax softened a little with some Venice turpentine. Before fixing the tin-foil, however, it must be properly spread over the mould, so as to remove every wrinkle; which the pliancy of the foil easily admits of, by uniform and well-directed pressure with the fingers.

The glass being placed in the hollow bed of a tight sack filled with fine sand, set in a well-jointed box capable of retaining quicksilver, its concave surface must be dusted with sifted wood-ashes, or Spanish white contained in a small cotton bag, and then well wiped with clean linen rags, to free it from all adhering impurity, and particularly the moisture of the breath. The concavity must be now filled with quicksilver to the very lip, and the mould being dipped a little way into it, is withdrawn, and the adhering mercury is spread over the tin with a soft flannel roll, so as to amalgamate and brighten its whole surface, taking every precaution against breathing on it. Whenever this brightening seems complete, the mould is to be immersed, not vertically, but one edge at first, and thus obliquely downwards till the centres coincide; the mercury meanwhile being slowly displaced, and the mark on the mould being brought finally into coincidence with the mark on the glass. The mould is now left to operate by its own weight, in expelling the superfluous mercury, which runs out upon the sand-bag and thence into a groove in the bottom of the box, whence it overflows by a spout into a leather bag of reception. After half an hour’s repose, the whole is cautiously inverted, to drain off the quicksilver more completely. For this purpose, a box like the first is provided with a central support rising an inch above its edges; the upper surface of the support being nearly equal in diameter to that of the mould. Two workmen are required to execute the following operation. Each steadies the mould with the one hand, and raises the box with the other, taking care not to let the mould be deranged, which they rest on the (convex) support of the second box. Before inverting the first apparatus, however, the reception bag must be removed, for fear of spilling its mercury. The redundant quicksilver now drains off; and if the weight of the sand-bag is not thought sufficient, supplementary weights are added at pleasure. The whole is left in this position for two or three days. Before separating the mirror from its mould, the border of tin-foil, fixed to it with wax, must be pared off with a knife. Then the weight and sand-bag being removed, the glass is lifted up with its interior coating of tin-amalgam.

For silvering a convex surface.--A concave plaster mould is made on the convex glass, and their points of coincidence are defined by marks. This mould is to be lined with tin-foil, with the precautions above described; and the tin surface being first brightened with a little mercury, the mould is then filled with the liquid metal. The glass is to be well cleaned, and immersed in the quicksilver bath, which will expel the greater part of the metal. A sand-bag is now to be laid on the glass, and the whole is to be inverted as in the former case on a support; when weights are to be applied to the mould, and the mercury is left to drain off for several days.

If the glass be of large dimensions, 30 or 40 inches, for example, another method is adopted. A circular frame or hollow ring of wood or iron is prepared, of twice the diameter of the mirror, supported on three feet. A circular piece of new linen cloth of close texture is cut out, of equal diameter to the ring, which is hemmed stoutly at the border, and furnished round the edge with a row of small holes, for lacing the cloth to the ring, so as to leave no folds in it, but without bracing it so tightly as to deprive it of the elasticity necessary for making it into a mould. This apparatus being set horizontally, a leaf of tin-foil is spread over it, of sufficient size to cover the surface of the glass; the tin is first brightened with mercury, and then as much of the liquid metal is poured on as a plane mirror requires. The convex glass, well cleaned, is now set down on the cloth, and its own weight, joined to some additional weights, gradually presses down the cloth, and causes it to assume the form of the glass which thus comes into close contact with the tin submersed under the quicksilver. The redundant quicksilver is afterwards drained off by inversion, as in common cases.

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