A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice (part 8 of 13)

A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice (part 8 of 13)

The liquor is often tinged yellow by carbon, after it has ceased to contain a single trace of iron oxide. As soon as litmus paper begins to be blued by carbonate of ammonia, we should stop adding it; immediately throw the whole upon a filter, and wash continuously with cold water. What passes through is to be neutralized with muriatic acid, and concentrated by evaporation. It may contain besides manganese, some lime, or barytes. It should therefore be precipitated with hydrosulphuret of ammonia, the hydrosulphuret of manganese should be collected, dissolved in strong muriatic acid, filtered, and treated, at a boiling heat, with carbonate of potash. The precipitate, well washed and calcined, contains, in 100 parts, 72·75 parts of metallic manganese.

The copper, arsenic, lead, tin, bismuth, antimony, or silver, are best separated by a stream of sulphuretted hydrogen gas passed through the solution in nitro-muriatic acid, after it is largely diluted with water. The precipitate must be cautiously roasted in a porcelain test, to burn away the large quantity of sulphur which is deposited in consequence of the conversion of the peroxide of iron into the protoxide. If nothing remains upon the test, none of these metals is present. If a residuum be obtained, it must be dissolved in nitro-muriatic acid, and subjected to examination. But, in fact, carbon, sulphur, phosphorus, silicon, and manganese, are the chief contaminators of iron.

Chloride of silver affords the means of determining the proportion of carbon contained in iron, and of ascertaining the state in which that substance exists in the metal. Fused chloride of a pale yellow colour must be employed. The operation is to be performed in close vessels, with the addition of a great deal of water, and a few drops of muriatic acid. The carbonaceous residuum is occasionally slightly acted upon. We may judge of this circumstance by the gases disengaged, as well as by the appearance of the charcoal.

Ductile iron and soft steel, as well as white cast-iron which has been rendered gray by roasting, when decomposed by chloride of silver, afford a blackish-brown unmagnetic charcoal, and a plumbaginous substance perfectly similar to what is extracted from the same kinds of iron, by solution in acids. A portion of this plumbago is also converted into charcoal of a blackish brown colour, by the action of the chloride. Hence this agent does not afford the means of obtaining what has been called the poly-carburet, till it has produced a previous decomposition. But we obtain it, in this manner, purer and in greater quantity than we could by dissolving the metal in the acids. The only subject of regret is, that we possess no good criterion for judging of the progress of this analytical operation.

Gray cast iron leaves, besides the polycarburet, a residuum of plumbago, and carbon which was not chemically combined with the iron; while tempered steel and white cast iron afford merely a blackish brown charcoal; but the operation is extremely slow with the latter two bodies, because a layer of charcoal forms upon the surface, which obstructs their oxidizement. For this reason the white cast iron ought to be previously changed into gray by fusion in a crucible lined with charcoal, before being subjected to the chloride of silver; if this process be employed for tempered steel, the combined carbon becomes merely a polycarburet. It would not be possible to operate upon more than 15 grains, which require from 60 to 80 times that quantity of the chloride, and a period of 15 days for the experiment.

The residuum, which is separable from the silver only by mechanical means, should be dried a long time at the heat of boiling water. It contains almost always iron and silica. After its weight is ascertained, it is to be burned in a crucible of platinum till the ashes no longer change their colour, and are not attractable by the magnet. The difference between the weights of the dried and calcined residuum is the weight of the charcoal. The oxide of iron is afterwards separated from the silica by muriatic acid.

In operating upon gray cast iron, we should ascertain separately the proportion of graphite or plumbago, and that of the combined charcoal. To determine the former, we dissolve a second quantity of the cast iron in nitric acid, with a little muriatic; the residuum, which is graphite, is separated from the silica and the combined carbon by the action of caustic potash. After being washed and dried, it must be weighed. The weight of the graphite obtained being deducted from the quantity of carbon resulting from the decomposition effected by the chloride of silver, the remainder is the amount of the chemically combined carbon.

By employing muriatic acid, we could dissipate at once the combined carbon; but this method would be inexact, because the hydrogen disengaged would carry off a portion of the graphite.

According to Karsten, Mushet’s table of the quantities of carbon contained in different steels and cast irons is altogether erroneous. It gives no explanation why, with equal proportions of charcoal, cast iron constitutes at one time a gray, soft, granular metal, and at another, a white, hard, brittle metal in lamellar facets. The incorrectness of Mushet’s statement becomes most manifest when we see the white lamellar cast iron melted in a crucible lined with charcoal, take no increase of weight, while the gray cast iron treated in the same way becomes considerably heavier.

Analysis has never detected a trace of carbon unaltered or of graphite in white cast iron, if it did not proceed from small quantities of the gray mixed with it; while perfect gray cast iron affords always a much smaller quantity of carbon altered by combination, and a much greater quantity of graphite. Neither kind of cast iron, however, betrays the presence of any oxygen. Steel affords merely altered carbon, without graphite; the same thing holds true of malleable iron; while the iron obtained by fusion with 25 per cent. of scales of iron contains no carbon at all.

The graphite of cast iron is obtained in scales of a metallic aspect, whereas the combined carbon is obtained in a fine powder. When the white cast iron has been roasted, and become gray, and is as malleable as the softest gray cast iron, it still affords no graphite as the latter does, though in appearance both are alike. Yet in their properties they are still essentially dissimilar.

With 4-1/4 per cent. of carbon, the white cast iron preserves its lamellar texture; but with less carbon, it becomes granular and of a gray colour, growing paler as the dose of carbon is diminished, while the metal after passing through an indefinite number of gradations, becomes steely cast iron, very hard steel, soft steel, and steely wrought iron.

The steels of the forge and the cast steels examined by Karsten, afforded him from 2·3 to 1-1/4 per cent. of carbon; in the steel of cementation, (blistered steel) he never found above 1-3/4 of carbon. Some wrought irons which ought to contain no charcoal, hold as much as 1/2 per cent. and they then approach to steel in nature. The softest and purest irons contain still 0·2 per cent. of carbon.

The quantity of graphite which gray cast iron contains, varies, according to Karsten’s experiments, from 2·57 to 3·75 per cent.; but it contains besides, some carbon in a state of alteration. The total contents in carbon varied from 3·15 to 4·65 per cent. When the congelation of melted iron is very slow, the carbon separates, probably in consequence of its crystallizing force, so as to form a gray cast iron replete with plumbago. If the gray do not contain more charcoal than the white from which it has been formed, and if it contain the charcoal in the state of mechanical mixture, then it can have little or none in a state of combination, even much less than what some steels contain. Hence we can account for some of its peculiarities in reference to white cast iron; such as its granular texture, its moderate hardness, the length of time it requires to receive annealing colours, the modifications it experiences by contact of air at elevated temperatures, the high degree of heat requisite to fuse it, its liquidity, and finally its tendency to rust by porosity, much faster than the white cast iron.

We thus see that carbon may combine with iron in several manners; that the gray cast iron is a mixture of steely iron and plumbago; that the white, rendered gray and soft by roasting, is a compound of steely iron and a carburet of iron, in which the carbon predominates; and that untempered steel is in the same predicament.

For the following analyses of cast irons, we are indebted to MM. Gay Lussac and Wilson.

TABLE.--In 100 parts.

+----------------------+------+-----+-----+-----+-------+------------+ | Cast iron. |Iron. |Car- |Sili-|Phos-| Man- | Remarks. | | | |bon. | ca. |pho- |ganese.| | | | | | |rus. | | | +----------------------+------+-----+-----+-----+-------+------------+ |White cast from Siegen|94·338|2·690|0·230|0·162|2·590 |By wood | | | | | | | | charcoal | |Do. Coblentz |94·654|2·441|0·230|0·185|2·490 | do. | |Do. a. d. Champ |96·133|2·324|0·840|0·703|a trace| do. | |Do. Isère |94·687|2·636|0·260|0·280|2·137 | do. | |Gray Nivernais |95·673|2·254|1·030|1·043|a trace| do. | |Do. Berry |95·573|2·319|1·920|0·188| do |Mix. of coke| | | | | | | | & do.| |Do. a. d. Champ |95·971|2·100|1·060|0·869| do. |Charcoal | |Do. Creusot |93·385|2·021|3·490|0·604| do. |Coke | |Do. a. d. Franche | | | | | | | | Comté |95·689|2·800|1·160|0·351| do. | do. | |Do. Wales |94·842|1·666|3·000|0·492| do. | do. | |Do. Do. |95·310|2·550|1·200|0·440| do. | do. | |Do. Do. |95·150|2·450|1·620|0·780| do. | do. | +----------------------+------+-----+-----+-----+-------+------------+

Karsten has given the following results as to carbon, in 100 parts of gray cast iron.

+--------------------------------+-----+----+----+----------------+ | Gray cast iron. |Com- |Free|To- | Remarks. | | |bined|car-|tal | | | |car- |bon.|car-| | | |bon. | |bon.| | +--------------------------------+-----+----+----+----------------+ |Siegen, from brown iron-stone | 0·89|3·71|4·60|By wood charcoal| |Siegen (Widderstein), from brown| | | | | |and sparry iron | 1·03|3·62|4·65| do. | |Malapane, from spherosiderite | 0·75|3·15|3·90| do. | |Königshütte, from brown ore | 0·58|2·57|3·15| coke | |Do. at a lower smelting heat | 0·95|2·70|3·65| do. | +--------------------------------+-----+----+----+----------------+

Fig. 607. represents in section, and fig. 606. in plan, the famous cupola furnace for casting iron employed at the Royal Foundry in Berlin. It rests upon a foundation a, from 18 to 24 inches high, which supports the basement plate of cast iron, furnished with ledges, for binding the lower ends of the upright side plates or cylinder, e. Near the mouth there is a top-plate d, made in several pieces, which serves to bind the sides at their upper end, as also to cover in the walls of the shaft. These plates are most readily secured in their places by screws and bolts. Within this iron case, at a little distance from it, the proper furnace-shaft e, is built with fire-bricks, and the space between this and the iron is filled up with ashes. The sole of the hearth f, over the basement-plate, is composed of a mixture of fire-clay and quartz-sand firmly beat down to the thickness of 6 or 8 inches, with a slight slope towards the discharge-hole for running off the metal. g is the form or the tuyère (there are sometimes one on each side); h the nose pipe; the discharge aperture i is 12 inches wide and 15 inches high; across which the sole of the hearth is rammed down. During the melting operation, this opening is filled up with fire-clay; when it is completed, a small hole merely is pierced through it at the lowest point, for running off the liquid metal. The hollow shaft should be somewhat wider at bottom than at top. Its dimensions vary with the magnitude of the foundry. When 5 feet high, its width at the level of the tuyère or blast-hole may be from 20 to 22 inches. From 250 to 300 cubic feet of air per minute are required for the working of such a cupola. For running down 100 pounds of iron, after the furnace has been brought to its heat, 48 pounds of ordinary coke are used; but with the hot blast much less will suffice. The furnace requires feeding with alternate charges of coke and iron every 8 or 10 minutes. The waste of iron, by oxidization and slag, amounts in most foundries to fully 5 per cent. For carrying off the burnt air, a chimney-hood is commonly erected over the cupola. See FOUNDRY.

The double-arched air or wind-furnace used in the foundries of Staffordshire for melting cast iron, has been found advantageous in saving fuel, and preventing waste by slag. It requires fire-bricks of great size and the best composition.

The main central key-stone is constructed of large fire-bricks made on purpose; against that key-stone the two arches press, having their abutments at the sides against the walls. The highest point of the roof is only 8 inches above the melted metal. The sole of the hearth is composed of a layer of sand 8 inches thick, resting upon a bed of iron or of brickwork. The edge of the fire-bridge is only 3 inches above the fluid iron.

In from 2 to 4 hours from 1 to 3 tons of metal may be founded in such a furnace, according to its size; but it ought always to be heated to whiteness before the iron is introduced. 100 pounds of cast iron require from 1 to 1-1/2 cubic foot of coal to melt them. The waste varies from 5 to 9 per cent.

I shall conclude the subject of iron with a few miscellaneous observations and statistical tables. Previously to the discovery by Mr. Cort, in 1785, of the methods of puddling and rolling or shingling iron, this country imported 70,000 tons of this metal from Russia and Sweden; an enormous quantity for the time, if we consider that the cotton and other automatic manufactures, which now consume so vast a quantity of iron, were then in their infancy; and that two years ago, the whole of our importation from these countries did not exceed 40,000 tons. From the following table of the prices of bar iron in successive years, we may infer the successive rates of improvement and economy, with slight vicissitudes.

+------+-----------------+ |Years.| Per Ton. | +------+-----------------+ | |£ s. £ s.| | 1824 | 9 0 to 10 0 | | 1825 |10 0 -- 14 0 | | 1826 | 8 10 -- 10 0 | | 1827 | 8 0 -- 9 0 | | 1828 | 7 10 -- 8 0 | | 1829 | 5 10 -- 7 0 | | 1830 | 5 5 -- 6 0 | | 1831 | 5 5 -- 5 10 | | 1832 | 5 0 -- 5 10 | | 1833 | 5 10 -- 6 0 | | 1834 | 6 0 -- 6 10 | | 1835 | 5 10 -- 7 0 | +------+-----------------+

I have been informed upon good authority that the total production of iron in Great Britain, in the year 1836, was almost exactly ONE MILLION OF TONS!

The export of iron that year, in bars, rods, pigs, castings, wire, anchors, hoops, nails, and old iron, amounted to 189,390 tons; in unwrought steel to 3,014, and in cutlery, to 21,072; in whole to 213,478: leaving apparently for internal consumption 776,522 tons, from which however one tenth probably should be deducted for waste, in the conversion of the bar iron. Hence 700,000 tons may be taken as the approximate quantity of iron made use of in the United Kingdom, in the year 1836.

The years 1835 and 1836 being those of the railway mania over the world, produced a considerable temporary rise in the price of bar iron; but as this increased demand caused the construction of a great many more smelting and refining furnaces, it has tended eventually to lower the prices; an effect also to be ascribed to the more general use of the hot blast.

The relative cost of making cast iron at Merthyr Tydvil in South Wales, and at Glasgow, was as follows, eight or nine years ago.

At Merthyr.

s. Tons. Cwts. Qrs. £ s. d. Raw mine at 10 per ton, 3 7 0 1 13 6 Coal at 6 2 16 0 0 16 6 Limestone 1 5 2 0 1 4 Other charges 0 9 1 -------- Total Cost 3 0 5

At Glasgow.

s. d. Tons. Cwts. £ s. d. Raw mine at 4 6 3 10 0 16 3 Splint Coal at 2 5 5 15 0 14 0 Limestone at 0 3 0 14 0 3 6 Coals for the engine 1 10 0 3 0 Other charges 1 1 0 -------- Total cost 2 17 9

The cost is still nearly the same at Merthyr, but it has been greatly decreased at Glasgow.

The saving of fuel by the hot-blast is said to be in fact so great, that blowing cylinders, which were adequate merely to work three furnaces at the first period, were competent to work four furnaces at the last period. The saving of materials has moreover been accompanied by an increase of one-fourth in the quantity of iron, in the same time; as a furnace which turned out only 60 tons a week with the cold blast, now turns out no less than 80 tons. That the iron so made is no worse, but probably better, when judiciously smelted, would appear from the following statement. A considerable order was not long since given to four iron-work companies in England, to supply pipes to one of the London water companies. Three of these supplied pipes made from the cold-blast iron; the fourth, it is said, supplied pipes made with the hot-blast iron. On subjecting these several sets of pipes to the requisite trials by hydraulic pressure, the last lot was found to stand the proof far better than any of the former three.--That iron was made with raw coal.

I have been since told by eminent iron-masters of Merthyr, that this statement stands in need of confirmation, or is probably altogether apocryphal, and that as they find the hot blast weakens the iron, they will not adopt it.

Between the cast irons made in different parts of Great Britain, there are characteristic differences. The Staffordshire metal runs remarkably fluid, and makes fine sharp castings. The Welsh is strong, less fluent, but produces bar iron of superior quality. The Derbyshire iron also forms excellent castings, and may be worked with care into very good bar iron. The Scotch iron is very valuable for casting into hollow wares, as it affords a beautiful smooth skin from the moulds, so remarkable in the castings of the Carron company, in Stirlingshire, and of the Phœnix foundry, at Glasgow. The Shropshire iron resembles the Staffordshire in its good qualities.

The average quantity of fine metal obtainable from the forge-pigs at Merthyr Tydvil, from the finery furnace, is one ton for 22-1/2 cwt. of cast iron, with a consumption of about 9-1/2 cwt. of coal per ton.

Estimate of the average cost of erecting three blast furnaces.

BUILDING EXPENSES.

Foundations _£_480 Masonry of hewn grit-stones 600 Common bricklayers’ work 1200 Lining of the furnace, hearth, &c., in fire-bricks 1140 Fire-clay for building 80 Lime and sand 800

CAST IRON.

Cast-iron pieces, such as dam-plates, tymp-plates, beams, tuyère-plates, &c., weighing about 24 tons for each furnace;--in whole 1140

WROUGHT IRON.

For the binding-hoops, keys, &c.; 5 tons for each 300

COST OF LABOUR.

Bricklayers, masons, and labourers in building 1080

VARIOUS EXPENSES.

Scaffolding 48 Tools 160 Shed in front of each furnace 480 Terracing, cost of ground, &c. 2400 ---- Total cost of erecting the furnaces 9908

INCIDENTAL CHARGES.

Blowing machinery, and steam engine of 80-horse power 6400 Inclined railway for mounting the charges 120 Gallery for charging 160 Steam engine house 400 Chimneys, boilers, &c. 480 Roasting kilns 480 Coke kilns 800 Dwelling-houses for workmen 800 ------ Total cost of 3 furnaces complete _£_19,548

Estimate from the Neath-Abbey Works in S. Wales, of the cost of machines requisite for a forge and shingling-mill, capable of turning out 120 tons of bar iron per week.

1. Steam-engine upon Bolton and Watt’s construction; of 40 inches diameter in the cylinder, and 8-feet stroke; with boilers, pipes, grate, bars, fire-doors, &c. &c., complete _£_1600 2. System of great-geering for transmitting the crank-motion of the engine to the mill-work, with fly-wheel, &c. 1090 3. A system of roughing rolls, with pinions, uprights, and every thing else necessary 525 4. Two pairs of finisher-rolls, with all their accessories 525 5. Two pairs of shear-machines, at 170_l._ apiece 340 6. One pair of rolls of 10 inches diameter, for making small bar iron, with all their accessories 230 7. Forge hammer, including the anvil, the cam-shafts, and all the other requisites 185 8. A complete turning lathe 200 ------ _£_4695 9. To the above must be added, spare cylinders weighing about 60 tons 960 10. Duplicate articles for the steam-engine ? 11. 150 tons of cast-iron plates, to cover the floor of the mill 900 12. Eight tons of cast-iron pieces for a reverberatory furnace 52 13. Tools of malleable iron; rakes, oars, &c. 28 14. Castings for mounting a cupola furnace 50 15. Blowing-machine for the cupola 80 16. Pieces of iron for a small forge, with two fires, two bellows, two anvils, iron tools faced with steel, and common iron tools, &c. 100 17. Eight tons of cast-iron pieces, and wrought-iron pieces for 14 puddling furnaces 983 18. Seven tons of cast-iron pieces, and wrought iron for 4 re- heating furnaces 252 19. Tools for the puddlers and other workmen 15 20. Iron mountings for two cranes, partly made of wood 50 ------- Total cost of machines, and pieces of iron _£_8165

To the above, the cost of the steam engine house is to be added, that of another forge hammer, and incidental expenses.

In Staffordshire the following estimate has been given:

A steam-engine of 60-horse power 2016 Rolls, with the iron work of the furnaces, &c., to make 120 tons of bar iron weekly 2572 ------- _£_4588

The Neath-Abbey estimate is greater, but that company has a high character for making substantial well-finished machinery.

Bar iron made entirely from ore without admixture of cinder, or vitrified oxide, is always reckoned worth 10_s._ a ton more than the average iron in the market, which is frequently made by smelting 25 per cent. of cinder with 75 of ore or mine, as it is called.

Importation of iron in bars or unwrought, for home consumption; and amount of duty, in

1836. 1837. 1836. 1837. 18,978 tons 18 cwt. | 13,470 tons 4 cwt. | _£_28,450 | _£_20,065

M. Virlet’s Statistical Table of the produce of Iron in Europe.

Quintals. England (1827) 7,098,000 France (1834) 2,200,000 Russia (1834) 1,150,000 Austria (1829) 850,000 Sweden (1825) 850,000 Prussia 800,000 The Hartz Mountains 600,000 Holland and Belgium 600,000 Elba and Italy 280,000 Piedmont 200,000 Spain 180,000 Norway 150,000 Denmark 135,000 Bavaria 130,000 Saxony 80,000 Poland 75,000 Switzerland 30,000 Savoy 25,000 ---------- Total 13,433,000 (equal to about 672,000 tons.)

For additional statistics of iron, see PITCOAL, at the end.

Bronzing of polished iron.--The barrels of fowling-pieces and rifles are occasionally bronzed and varnished, to relieve the eye of the sportsman from the glare of a polished metal, and to protect the surface from rusting. The liquid used for browning the barrels is made by mixing nitric acid of specific gravity 1·2, with its own weight of spirit of nitric ether, of alcohol, and tincture of muriate of iron; and adding to that mixture, a quantity of sulphate of copper equal in weight to the nitric acid and ethereous spirit taken together. The sulphate must be dissolved in water before being added; and the whole being diluted with about 10 times its weight of water, is to be bottled up for use. This liquid must be applied by friction with a rag to the clear barrel, which must then be rubbed with a hard brush; processes to be alternated two or three times. The barrel should be afterwards dipped in boiling water, rendered feebly alkaline with carbonate of potash or soda, well dried, burnished, and heated slightly for receiving several coats of tin-smith’s lacquer, consisting of a solution of shellac in alcohol, coloured with dragon’s blood.

ISINGLASS, or Fish-glue, called in Latin ichthyocolla, is a whitish, dry, tough, semi-transparent substance, twisted into different shapes, often in the form of a lyre, and consisting of membranes rolled together. Good isinglass is unchangeable in the air, has a leathery aspect, and a mawkish taste nearly insipid; when steeped in cold water it swells, softens, and separates in membranous laminæ. At the boiling heat it dissolves in water, and the solution, on cooling, forms a white jelly, which is semi-transparent, soluble in weak acids, but is precipitated from them by alkalies. It is gelatine nearly pure; and if not brittle, like other glue, this depends on its fibrous and elastic texture. The whitest and finest is preferred in commerce. Isinglass is prepared from the air-bladders of sturgeons, and especially the great sturgeon, the accipenser huso; which is fished on the shores of the Caspian sea, and in the rivers flowing into it, for the sake chiefly of its swim bladder.

The preparation of isinglass in this part of Russia, and particularly at Astracan, consists in steeping these bladders in water, removing carefully their external coat, and the blood which often covers them, putting them in a hempen bag, squeezing them, softening them between the hands, and twisting them into small cylinders, which are afterwards bent into the shape of a lyre. They are ready for the market immediately after being dried in the sun, and whitened with the fumes of burning sulphur.

In some districts of Moldavia, another process is followed. The skin, the stomach, the intestines, and the swim bladder of the sturgeon are cut in small pieces, steeped in cold water, and then gently boiled. The jelly thus obtained is spread in thin layers to dry, when it assumes the appearance of parchment. This being softened in a little water, then rolled into cylinders, or extended into plates, constitutes an inferior article.

The swim bladder of the cod and many other fishes, also furnishes a species of isinglass, but it is much more membranous, and less soluble than that of the sturgeon.

The properties of isinglass are the same as those of gelatine or pure glue; and its uses are very numerous. It is employed in considerable quantities to clarify ale, wine, liqueurs, and coffee. As an article of food to the luxurious in the preparation of creams and jellies, it is in great request. Four parts of it convert 100 of water into a tremulous jelly, which is employed to enrich many soups and sauces. It is used along with gum as a dressing to give lustre to ribbons and other silk articles. The makers of artificial pearls employ it to fix the essence d’Orient on the glass globules which form these pearls, and the Turks set their precious stones or jewellery by means of isinglass dissolved in alcohol along with gum ammoniac; a combination which is also employed in this country to join broken pieces of china and glass, under the name of diamond cement. That setting preserves its transparency after it solidifies, if it be well made.

It is by covering taffety or thin silk with a coat of isinglass that court plaster is made. A solution of isinglass coloured with carmine forms an excellent injection liquor to the anatomist. M. Rochen has made another pretty application of isinglass. He plunges into a limpid solution of it, made by means of a water bath, sheets of wire gauze set in window or lamp frames, which, when cold, have the appearance of glass, and answer instead of it for shades and other purposes. If one dip be not sufficient to make a proper transparent plate of isinglass, several may be given in succession, allowing each film to harden in the interval between the dips. The outer surface should be varnished to protect it from damp air. These panes of gelatine are now generally used for lamps instead of horn, in the maritime arsenals of France.

Isinglass imported for home consumption; and duties paid in

1835. 1836. 1835. 1836. 1,814 cwts. | 1,735 cwts. | _£_4,290 | _£_4,125

ISLAND MOSS (Lichen d’Islande, Fr.; Flechte Isl., Germ.); is a lichen, the Cetraria islandica, which contains a substance soluble in hot water, but forming a jelly when it cools, styled lichenine by M. Guerin. Lichenine has a yellowish tint in the dry state, is transparent in thin plates, insipid, inodorous, and difficult to pulverize. Cold water makes it swell, but does not dissolve it. It is precipitated in white flocks by alcohol and ether. Iodine tinges it of a brownish green. Sulphuric acid converts it into sugar; and the nitric into oxalic acid. Lichenine is prepared by extracting first of all from the plant a bitter colouring matter, by digesting 1 pound of it in 16 pounds of cold water containing 1 ounce of pearl-ash; then draining the lichen, edulcorating with cold water, and boiling it in 9 pounds of boiling water, till 3 pounds be evaporated. The jelly which forms, upon cooling the filtered solution, is dark coloured, but, being dried and redissolved in hot water, it becomes clear and colourless. Lichenine consists of 39·33 carbon, 7·24 hydrogen, and 55·43 oxygen. With potash, lime, oxide of lead, and tincture of galls, the habitudes of lichenine and starch are the same. The mucilage of island moss is preferred in Germany to common paste for dressing the warp of webs in the loom, because it remains soft, from its hygrometric quality. It is also mixed with the pulp for sizing paper in the vat.

IVORY (Ivoire, Fr.; Elfenbein, Germ.); is the osseous matter of the tusks teeth of the elephant, the hippopotamus, or morse, wild boar, several species of phocæ, as well as the horn or tooth of the narwhal. Ivory is a white, fine-grained, dense substance, of considerable elasticity, in thin plates, and more transparent than paper of equal thickness. The outside of the tusk is covered by the cortical part, which is softer and less compact than the interior substance, with the exception of the brown plate that sometimes lines the interior cavity. The hardest, toughest, whitest, and most translucent ivory, has the preference in the market; and the tusks of the sea-horse are considered to afford the best. In these, a rough glassy enamel covers the cortical part, of such hardness, as to strike sparks with steel. The horn of the narwhal is sometimes ten feet long, and consists of an ivory of the finest description, as hard as that of the elephant, and susceptible of a better polish; but it is not in general so much esteemed as the latter.

Ivory has the same constituents as the teeth of animals, three-fourths being phosphate, with a little carbonate of lime; one-fourth cartilage. See BONES.

It is extensively employed by miniature painters for their tablets; by turners, in making numberless useful and ornamental objects; by cutlers, for the handles of knives and forks; by comb-makers; as also by philosophical instrument makers, for constructing the scales of thermometers, &c. The ivory of the sea-horse is preferred by dentists for making artificial teeth; that of the East India elephant is better than of the African. When it shows cracks or fissures in its substance, and when a splinter broken off has a dull aspect, it is reckoned of inferior value. Ivory is distinguishable from bone by its peculiar semi-transparent rhombohedral net-work, which may be readily seen in slips of ivory cut transversely.

Ivory is very apt to take a yellow-brown tint by exposure to air. It may be whitened or bleached, by rubbing it first with pounded pumice-stone and water, then placing it moist under a glass shade luted to the sole at the bottom, and exposing it to sunshine. The sunbeams without the shade would be apt to occasion fissures in the ivory. The moist rubbing and exposure may be repeated several times.

For etching ivory, a ground made by the following recipe is to be applied to the polished surface:--Take of pure white wax, and transparent tears of mastick, each one ounce; asphalt, half an ounce. The mastick and asphalt having been separately reduced to fine powder, and the wax being melted in an earthenware vessel over the fire, the mastick is to be first slowly strewed in and dissolved by stirring; and then the asphalt in like manner. This compound is to be poured out into lukewarm water, well kneaded, as it cools, by the hand, into rolls or balls about one inch in diameter. These should be kept wrapped round with taffety. If white rosin be substituted for the mastick, a cheaper composition will be obtained, which answers nearly as well; 2 oz. asphalt, 1 oz. rosin, 1/2 oz. white wax; being good proportions. Callot’s etching ground for copper plates, is made by dissolving with heat 4 oz. of mastick in 4 oz. of very fine linseed oil; filtering the varnish through a rag, and bottling it for use.

Either of the two first grounds being applied to the ivory, the figured design is to be traced through it in the usual way, a ledge of wax is to be applied, and the surface is to be then covered with strong sulphuric acid. The effect comes better out with the aid of a little heat; and by replacing the acid, as it becomes dilute by absorption of moisture, with concentrated oil of vitriol. Simple wax may be employed instead of the copperplate engravers’ ground; and strong muriatic acid instead of sulphuric. If an acid solution of silver or gold be used for etching, the design will become purple or black, on exposure to sunshine. The wax may be washed away with oil of turpentine. Acid nitrate of silver affords the easiest means of tracing permanent black lines upon ivory.

Ivory may be dyed by using the following prescriptions:--

1. Black dye.--If the ivory be laid for several hours in a dilute solution of neutral nitrate of pure silver, with access of light, it will assume a black colour, having a slightly green cast. A still finer and deeper black may be obtained by boiling the ivory for some time in a strained decoction of logwood, and then steeping it in a solution of red sulphate or red acetate of iron.

2. Blue dye.--When ivory is kept immersed for a longer or shorter time in a dilute solution of sulphate of indigo (partly saturated with potash), it assumes a blue tint of greater or less intensity.

3. Green dye.--This is given by dipping blued ivory for a little while in solution of nitromuriate of tin, and then in a hot decoction of fustic.

4. Yellow dye--is given by impregnating the ivory first with the above tin mordant, and then digesting it with heat in a strained decoction of fustic. The colour passes into orange, if some brazil wood has been mixed with the fustic. A very fine unchangeable yellow may be communicated to ivory by steeping it 18 or 24 hours in a strong solution of the neutral chromate of potash, and then plunging it for some time in a boiling hot solution of acetate of lead.

5. Red dye--may be given by imbuing the ivory first with the tin mordant, then plunging it in a bath of brazil wood, cochineal, or a mixture of the two. Lac-dye may be used with still more advantage, to produce a scarlet tint. If the scarlet ivory be plunged for a little in a solution of potash, it will become cherry red.

6. Violet dye--is given in the logwood bath, to ivory previously mordanted for a short time with solution of tin. When the bath becomes exhausted, it imparts a lilac hue. Violet ivory is changed to purple-red by steeping it a little while in water containing a few drops of nitro-muriatic acid.

With regard to dyeing ivory, it may in general be observed, that the colours penetrate better before the surface is polished than afterwards. Should any dark spots appear, they may be cleared up by rubbing them with chalk; after which the ivory should be dyed once more to produce perfect uniformity of shade. On taking it out of the boiling hot dye bath, it ought to be immediately plunged into cold water, to prevent the chance of fissures being caused by the heat.

If the borings and chips of the ivory-turner, called ivory dust, be boiled in water, a kind of fine size is obtained.

The importation of elephants’ teeth for home consumption was, in 1834, 4,282 cwts.; in 1835, 3,698, and in 1836, 4,584 cwts.; duty, 1_l._ per cwt.

IVORY BLACK (Noir d’ivoire, Fr.; Kohle von Elfenbein, Germ.); is prepared from ivory dust, by calcination in the very same way as is described under BONE BLACK.

The calcined matter being ground and levigated on a porphyry slab, affords a beautiful velvety black, much used in copperplate printing. Ivory black may be prepared upon the small scale, by a well regulated ignition of the ivory dust in a covered crucible.

K.

KALI. The Arabs gave this name to an annual plant which grows near the sea-shore; now known under the name of salsola soda, and from whose ashes they extracted a substance, which they called alkali, for making soap. The term kali is used by German chemists to denote caustic potash; and kalium, its metallic basis; instead of our potassa and potassium, of preposterous pedigree, being derived from the words pot ashes, that is ashes prepared in a pot.

KAOLIN, (Terre à porcelaine, Fr.; Porzellanerde, Germ.), is the name given by the Chinese to the fine white clay with which they fabricate the biscuit of their porcelains. See CLAY. Berthier’s analyses of two porcelain earths are as follows:--

+-------------+------------+-----------------+ | Analyses. |From Passau.|From Saint Yriex.| +-------------+------------+-----------------+ |Silica | 45·06 | 46·8 | |Alumina | 32·00 | 37·3 | |Lime | 0·74 | -- | |Oxide of iron| 0·90 | -- | |Potass | -- | 2·5 | |Water | 18·0 | 13·0 | | +------------+-----------------+ | | 96·7 | 99·6 | +-------------+------------+-----------------+

KARABÉ, a name of amber, of Arabic origin, in use upon the Continent.

KELP; (Varec, Fr.; Wareck, Germ.), is the crude alkaline matter produced by incinerating various species of fuci, or sea-weed. They are cut with sickles from the rocks in the summer season, dried and then burned, with much stirring of the pasty ash. I have analyzed many specimens of kelp, and found the quantity of soluble matter in 100 parts of the best to be from 53 to 62, while the insoluble was from 47 to 38. The soluble consisted of--

Sulphate of Soda 8·0 19·0 Soda in carbonate and sulphuret 8·5 5·5 Muriate of soda and potash 36·5 37·5 ---- ---- 53·0 62·0

The insoluble matter consisted of--

Carbonate of lime 24·0 10·0 Silica 8·0 0·0 Alumina tinged with iron oxide 9·0 10·0 Sulphate of lime 0·0 9·5 Sulphur and loss 6·0 8·5 ----- ----- 100·0 100·0

The first of these specimens was from Heisker, the second from Rona, both in the isle of Skye, upon the property of Lord Macdonald. From these, and many other analyses which I have made, it appears that kelp is a substance of very variable composition, and hence it was very apt to produce anomalous results, when employed as the chief alkaline flux of crown glass, which it was for a very long period. The fucus vesiculosus and fucus nodosus are reckoned to afford the best kelp by incineration; but all the species yield a better product when they are of two or three years growth, than when cut younger. The varec, made on the shores of Normandy, contains almost no carbonate of soda, but much sulphate of soda and potash, some hyposulphate of potash, chloride of sodium, iodide of potassium, and chloride of potassium; the average composition of the soluble salts being, according to M. Gay Lussac, 56 of chloride of sodium, 25 of chloride of potassium, and a little sulphate of potash. The very low price at which soda ash, the dry crude carbonate from the decomposition of sea salt, is now sold, has nearly superseded the use of kelp, and rendered its manufacture utterly unprofitable--a great misfortune to the Highlands and Islands of Scotland.

KERMES. There are two substances so called, of totally different natures. Kermes mineral is merely a factitious sulphuret of antimony in a state of impalpable comminution, prepared in the moist way. Its minute examination belongs to pharmaceutical chemistry. It may be obtained perfectly pure, by diluting the proto-chloride of antimony with solution of tartaric acid, and precipitating the metal with sulphuretted hydrogen; or by exposing the finely levigated native sulphuret to a boiling solution of carbonate of potash for some time, and filtering the liquor while boiling hot. The kermes falls down in a brown-red powder, as the liquor cools.

Kermes-grains, alkermes, are the dried bodies of the female insects of the species coccus ilicis, which lives upon the leaves of the quercus ilex (prickly oak). The word kermes is Arabic, signifies little worm. In the middle ages, this dye stuff was therefore called vermiculus in Latin, and vermillion in French. It is curious to consider how the name vermillion has been since transferred to red sulphuret of mercury.

Kermes has been known in the East since the days of Moses; it has been employed from time immemorial in India to dye silk; and was used also by the ancient Greek and Roman dyers. Pliny speaks of it under the name of coccigranum, and says that there grew upon the oak in Africa, Sicily, &c. a small excrescence like a bud, called cusculium; that the Spaniards paid with these grains, half of their tribute to the Romans; that those produced in Sicily were the worst; that they served to dye purple; and that those from the neighbourhood of Emerita in Lusitania (Portugal) were the best.

In Germany, during the ninth, twelfth, thirteenth, and fourteenth centuries, the rural serfs were bound to deliver annually to the convents, a certain quantity of kermes, the coccus polonicus, among the other products of husbandry. It was collected from the trees upon Saint John’s day, between eleven o’clock and noon, with religious ceremonies, and was therefore called Johannisblut, (Saint John’s blood), as also German cochineal. At the above period, a great deal of the German kermes was consumed in Venice, for dyeing the scarlet to which that city gives its name. After the discovery of America, cochineal having been introduced, began to supersede kermes for all brilliant red dyes.

The principal varieties of kermes are the coccus quercus, the coccus polonicus, the coccus fragariæ, and the coccus uva ursi.

The coccus quercus insect lives in the south of Europe upon the kermes oak. The female has no wings, is of the size of a small pea, of a brownish-red colour, and is covered with a whitish dust. From the middle of May to the middle of June the eggs are collected, and exposed to the vapour of vinegar, to prevent their incubation. A portion of eggs is left upon the tree for the maintenance of the brood. In the department of the Bouches-du-Rhone, one half of the kermes crop is dried. It amounts annually to about 60 quintals or cwts., and is warehoused at Avignon.

The kermes of Poland, or coccus polonicus, is found upon the roots of the scleranthus perennis and the scleranthus annuus, in sandy soils of that country and the Ukraine. This species has the same properties as the preceding; one pound of it, according to Wolfe, being capable of dyeing 10 pounds of wool; but Hermstaedt could not obtain a fine colour, although he employed 5 times as much of it as of cochineal. The Turks, Armenians, and Cossacks, dye with kermes, their morocco leather, cloth, silk, as well as the manes and tails of their horses.

The kermes called coccus fragariæ, is found principally in Siberia, upon the root of the common strawberry.

The coccus uva ursi is twice the size of the Polish kermes, and dyes with alum a fine red. It occurs in Russia.

Kermes is found not only upon the lycopodium complanatum in the Ukraine, but upon a great many other plants.

Good kermes is plump, of a deep red colour, of an agreeable smell, and a rough and pungent taste. Its colouring matter is soluble in water and alcohol; it becomes yellowish or brownish with acids, and violet or crimson with alkalis. Sulphate of iron blackens it. With alum it dyes a blood-red; with copperas an agate gray; with copperas and tartar, a lively gray; with sulphate of copper and tartar, an olive green; with tartar and salt of tin, a lively cinnamon yellow; with more alum and tartar, a lilac; with sulphate of zinc and tartar, a violet. Scarlet and crimson dyed with kermes, were called grain colours; and they are reckoned to be more durable than those of cochineal, as is proved by the brilliancy of the old Brussels tapestry.

Hellot says that previous to dyeing in the kermes bath, he threw a handful of wool into it, in order to extract a blackish matter, which would have tarnished the colour. The red caps for the Levant are dyed at Orleans with equal parts of kermes and madder; and occasionally with the addition of some Brazil wood.

Cochineal and lac-dye have now nearly superseded the use of kermes as a tinctorial substance, in England.

KILLAS, is the name by which clay-slate is known among the Cornish miners.

KILN; (Four, Fr.; Ofen, Germ.) is the name given to various forms of furnaces and stoves, by which an attempered heat may be applied to bodies; thus there are brick-kilns, hop-kilns, lime-kilns, malt-kilns, pottery-kilns. Hop and malt kilns, being designed merely to expel the moisture of the vegetable matter, may be constructed in the same way. See BRICK, LIMESTONE, MALT, POTTERY, for a description of their respective kilns.

KINIC ACID; a peculiar acid extracted by Vauquelin from cinchona.

KINO, is an extractive matter obtained from the nauclea gambir, a shrub which grows at Bancoul and Sumatra, but principally in Prince of Wales’ Island. It is of a reddish-brown colour, has a bitter styptic taste, and consists chiefly of tannin. It is used only as an astringent in medicine. Kino is often called a gum, but most improperly.

KIRSCHWASSER, is an alcoholic liquor obtained by fermenting and distilling bruised cherries, called kirschen in German. The cherry usually employed in Switzerland and Germany is a kind of morello, which on maturation becomes black, and has a kernel very large in proportion to its pulp. When ripe, the fruit being made to fall by switching the trees, is gathered by children, thrown promiscuously, unripe, ripe, and rotten into tubs, and crushed either by hand, or with a wooden beater. The mashed materials are set to ferment, and whenever this process is complete, the whole is transferred to an old still covered with verdigris, and the spirit is run off in the rudest manner possible, by placing the pot over the common fire-place.

The fermented mash is usually mouldy before it is put into the alembic, the capital of which is luted on with a mixture of mud and dung. The liquor has accordingly, for the most part, a rank smell, and is most dangerous to health, not only from its own crude essential oil, but from the prussic acid, derived from the distillation of the cherry-stones.

There is a superior kind of kirschwasser made in the Black Forest, prepared with fewer kernels, from choice fruit, properly pressed, fermented, and distilled.

KNOPPERN, are excrescences produced by the puncture of an insect upon the flower-cups of several species of oak. They are compressed or flat, irregularly pointed, generally prickly and hard; brown when ripe. They abound in Styria, Croatia, Sclavonia, and Natolia; those from the latter country being the best. They contain a great deal of tannin, are much employed in Austria for tanning, and in Germany for dyeing fawn, gray, and black. Wool, with a mordant of sulphate of zinc, takes a grayish nankeen colour. See GALLS.

KOUMISS, is the name of a liquor which the Calmucs make by fermenting mare’s milk, and from which they distil a favourite intoxicating spirit, called rack or racky. Cow’s milk is said to produce only one third as much spirit, from its containing probably less saccharine matter.

The milk is kept in bottles made of hides, till it becomes sour, is shaken till it casts up its cream, and is then set aside in earthen vessels in a warm place to ferment, no yeast being required, though sometimes a little old koumiss is added. 21 pounds of milk put into the still afford 14 ounces of low wines, from which 6 ounces of pretty strong alcohol, of an unpleasant flavour, are obtained by rectification.

L.

LABDANUM or LADANUM, is an unctuous resin, of an agreeable odour, found besmearing the leaves and twigs of the cystus creticus, a plant which grows in the island of Candia, and in Syria. It is naturally a dark-brown soft substance, but it hardens on keeping. Its specific gravity is 1·186. It has a bitter taste. Its chief use is in surgery for making plasters.

LABRADORITE; opaline or Labradore felspar, is a beautiful mineral, with brilliant changing colours, blue, red, and green, &c. Spec. grav. 2·70 to 2·75. Scratches glass; affords no water by calcination; fusible at the blow-pipe into a frothy bead; soluble in muriatic acid; solution affords a copious precipitate with oxalate of ammonia. Cleavages of 93-1/2° and 86-1/2°; one of which is brilliant and pearly. Its constituents are, silica, 55·75; alumina, 26·5; lime, 11; soda, 4; oxide of iron, 1·25; water, 0·5.

LABYRINTH, in metallurgy, means a series of canals distributed in the sequel of a stamping-mill; through which canals a stream of water is transmitted for suspending, carrying off, and depositing, at different distances, the ground ores. See METALLURGY.

LAC, LAC-DYE. (Laque, Fr.; Lack, Lackfarben, Germ.) Stick-lac is produced by the puncture of a peculiar female insect, called coccus lacca or ficus, upon the branches of several plants; as the ficus religiosa, the ficus indica, the rhamnus jujuba, the croton lacciferum, and the butea frondosa, which grow in Siam, Assam, Pegu, Bengal, and Malabar. The twig becomes thereby encrusted with a reddish mammelated resin, having a crystalline-looking fracture.

The female lac insect is of the size of a louse; red, round, flat, with 12 abdominal circles, a bifurcated tail, antennæ, and 6 claws, half the length of the body. The male is twice the above size, and has 4 wings; there is one of them to 5000 females. In November or December the young brood makes its escape from the eggs, lying beneath the dead body of the mother; they crawl about a little way, and fasten themselves to the bark of the shrubs. About this period the branches often swarm to such a degree with this vermin, that they seem covered with a red dust; in this case, they are apt to dry up, by being exhausted of their juices. Many of these insects, however, become the prey of others, or are carried off by the feet of birds, to which they attach themselves, and are transplanted to other trees. They soon produce small nipple-like incrustations upon the twigs, their bodies being apparently glued, by means of a transparent liquor, which goes on increasing to the end of March, so as to form a cellular texture. At this time, the animal resembles a small oval bag, without life, of the size of cochineal. At the commencement, a beautiful red liquor only is perceived, afterwards eggs make their appearance; and in October or November, when the red liquor gets exhausted, 20 or 30 young ones bore a hole through the back of their mother, and come forth. The empty cells remain upon the branches. These are composed of the milky juice of the plant, which serves as nourishment to the insects, and which is afterwards transformed or elaborated into the red colouring matter that is found mixed with the resin, but in greater quantity in the bodies of the insects, in their eggs, and still more copiously in the red liquor secreted for feeding the young. After the brood escapes, the cells contain much less colouring matter. On this account, the branches should be broken off before this happens, and dried in the sun. In the East Indies this operation is performed twice in the year; the first time in March, the second in October. The twigs encrusted with the radiated cellular substance, constitute the stick-lac of commerce. It is of a red colour more or less deep, nearly transparent, and hard, with a brilliant conchoidal fracture. The stick-lac of Siam is the best; a piece of it presented to me by Mr. Rennie, of Fenchurch-street, having an incrustation fully one quarter of an inch thick all round the twig. The stick-lac of Assam ranks next; and, last, that of Bengal, in which the resinous coat is scanty, thin, and irregular. According to the analysis of Dr. John, stick-lac consists, in 120 parts, of

An odorous common resin 80·00 A resin insoluble in ether 20·00 Colouring matter analogous to that of cochineal 4·50 Bitter balsamic matter 3·00 Dun yellow extract 0·50 Acid of the stick-lac (laccic acid) 0·75 Fatty matter, like wax 3·00 Skins of the insects, and colouring matter 2·50 Salts 1·25 Earths 0·75 Loss 4·75 ------ 120·00

According to Franke, the constituents of stick-lac are, resin, 65·7; substance of the lac, 28·3; colouring matter, 0·6.

Seed-lac.--When the resinous concretion is taken off the twigs, coarsely pounded, and triturated with water in a mortar, the greater part of the colouring matter is dissolved, and the granular portion which remains being dried in the sun, constitutes seed-lac. It contains of course less colouring matter than the stick-lac, and is much less soluble. John found in 100 parts of it, resin, 66·7; wax, 1·7; matter of the lac, 16·7; bitter balsamic matter, 2·5; colouring matter, 3·9; dun yellow extract, 0·4; envelopes of insects, 2·1; laccic acid, 0·0; salts of potash and lime, 1·0; earths, 6·6; loss, 4·2.

In India the seed-lac is put into oblong bags of cotton cloth, which are held over a charcoal fire by a man at each end, and, as soon as it begins to melt, the bag is twisted so as to strain the liquefied resin through its substance, and to make it drop upon smooth stems of the banyan tree (musa paradisa). In this way, the resin spreads into thin plates, and constitutes the substance known in commerce by the name of shell-lac.

The Pegu stick-lac, being very dark coloured, furnishes a shell-lac of a corresponding deep hue, and therefore of inferior value. The palest and finest shell-lac is brought from the northern Circar. It contains very little colouring matter. A stick-lac of an intermediate kind comes from the Mysore country, which yields a brilliant lac-dye and a good shell-lac.

Lac-dye is the watery infusion of the ground stick-lac, evaporated to dryness, and formed into cakes about two inches square and half an inch thick. Dr. John found it to consist of, colouring matter, 50; resin, 25; and solid matter, composed of alumina, plaster, chalk, and sand, 22.

Dr. Macleod, of Madras, informs me that he prepared a very superior lac-dye from stick-lac, by digesting it in the cold in a slightly alkaline decoction of the dried leaves of the Memecylon tinctorium (perhaps the M. capitellatum, from which the natives of Malabar and Ceylon obtain a saffron-yellow dye). This solution being used along with a mordant consisting of a saturated solution of tin in muriatic acid, was found to dye woollen cloth of a very brilliant scarlet hue.

The cakes of lac-dye imported from India, stamped with peculiar marks to designate their different manufacturers, are now employed exclusively in England for dyeing scarlet cloth, and are found to yield an equally brilliant colour, and one less easily affected by perspiration than that produced by cochineal. When the lac-dye was first introduced, sulphuric acid was the solvent applied to the pulverized cakes, but as muriatic acid has been found to answer so much better, it has entirely supplanted it. A good solvent (No. 1.) for this dye-stuff may be prepared by dissolving 3 pounds of tin in 60 pounds of muriatic acid, of specific gravity 1·19. The proper mordant for the cloth is made by mixing 27 pounds of muriatic acid of sp. grav. 1·17, with 1-1/2 pounds of nitric acid of 1·19; putting this mixture into a salt-glazed stone bottle, and adding to it in small bits at a time, grain tin, till 4 pounds be dissolved. This solution (No. 2.) may be used within twelve hours after it is made, provided it has become cold and clear. For dyeing; three quarters of a pint of the solvent No. 1. is to be poured upon each pound of the pulverized lac-dye, and allowed to digest upon it for six hours. The cloth before being subjected to the dye bath, must be scoured in the mill with fullers’ earth. To dye 100 pounds of pelisse cloth, a tin boiler of 300 gallons capacity should be filled nearly brimful with water, and a fire kindled under it. Whenever the temperature rises to 150° Fahr., a handful of bran, and half a pint of the solution of tin (No. 2.) are to be introduced. The froth, which rises as it approaches ebullition, must be skimmed off; and when the liquor boils, 10-1/2 pounds of lac-dye, previously mixed with 7 pints of the solvent No. 1., and 3-1/2 pounds of solution of tin No. 2., must be poured in. An instant afterwards, 10-1/2 pounds of tartar, and 4 pounds of ground sumach, both tied up in a linen bag, are to be suspended in the boiling bath for five minutes. The fire being now withdrawn, 20 gallons of cold water, with 10-1/2 pints of solution of tin being poured into the bath, the cloth is to be immersed in it, moved about rapidly during ten minutes; the fire is to be then re-kindled, and the cloth winced more slowly through the bath, which must be made to boil as quickly as possible, and maintained at that pitch for an hour. The cloth is to be next washed in the river; and lastly with water only, in the fulling mill. The above proportions of the ingredients produce a brilliant scarlet tint, with a slightly purple cast. If a more orange hue be wanted, white Florence argal may be used, instead of tartar, and some more sumach. Lac-dye may be substituted for cochineal in the orange-scarlets; but for the more delicate pink shades, it does not answer so well, as the lustre is apt to be impaired by the large quantity of acid necessary to dissolve the colouring matter of the lac.

Shell-lac, by Mr. Hatchett’s analysis, consists of resin, 90·5; colouring matter, 0·5; wax, 4·0; gluten, 2·8; loss, 1·8; in 100 parts.

The resin may be obtained pure by treating shell-lac with cold alcohol, and filtering the solution in order to separate a yellow gray pulverulent matter. When the alcohol is again distilled off, a brown, translucent, hard, and brittle resin, of specific gravity 1·139, remains. It melts into a viscid mass with heat, and diffuses an aromatic odour. Anhydrous alcohol dissolves it in all proportions. According to John, it consists of two resins, one of which dissolves readily in alcohol, ether, the volatile and fat oils; while the other is little soluble in cold alcohol, and is insoluble in ether and the volatile oils. Unverdorben, however, has detected no less than four different resins, and some other substances in shell-lac. Shell-lac dissolves with ease in dilute muriatic and acetic acids; but not in concentrated sulphuric acid. The resin of shell-lac has a great tendency to combine with salifiable bases; as with caustic potash, which it deprives of its alkaline taste.

This solution, which is of a dark red colour, dries into a brilliant, transparent, reddish brown mass; which may be re-dissolved in both water and alcohol. By passing chlorine in excess through the dark-coloured alkaline solution, the lac-resin is precipitated in a colourless state. When this precipitate is washed and dried, it forms, with alcohol, an excellent pale-yellow varnish, especially with the addition of a little turpentine and mastic.

With the aid of heat, shell-lac dissolves readily in a solution of borax.

The substances which Unverdorben found in shell-lac are the following:

1. A resin, soluble in alcohol and ether;

2. A resin, soluble in alcohol, insoluble in ether;

3. A resinous body, little soluble in cold alcohol;

4. A crystallizable resin;

5. A resin, soluble in alcohol and ether, but insoluble in petroleum, and uncrystallizable.

6. The unsaponified fat of the coccus insect, as well as oleic and margaric acids.

7. Wax.

8. The laccine of Dr. John.

9. An extractive colouring matter.

STATISTICAL TABLE of LAC-DYE and LAC-LAKE, per favour of James Wilkinson, Esq., of Leadenhall-street.

+----+---------+-------+-------------+-------------+---------+ | | Import. |Export.| Home | Prices. | Stocks. | | | | |Consumption. | | | +----+---------+-------+-------------+-------------+---------+ | | lbs. | lbs.| lbs. |s. d. s. d.|Chests.| |1802| 253| none | none | | | |1803| 1,735| |accot. burned| | | |1804| 531| | | | | |1805| 1,987| | | | | |1806| none | | | | | |1807| 25,350| | | | | |1808| 5,731| | | | | |1809| 40,632| | | | | |1810| 235,154| | | | | |1811| 378,325| | | | | |1812| 198,250| | | | | |1813| 289,654| | | | | |1814| 278,899| 5,071| 133,935 | | | |1815| 598,592| 8,441| 137,915 | | | |1816| 269,373| 27,412| 162,894 | | | |1817| 384,909| 23,091| 234,763 | | | |1818| 242,572| 32,079| 323,169 | | | |1819| 179,511| 21,707| 207,063 | | | |1820| 441,486| 49,519| 912,514 | | | |1821| 641,755| 91,925| 322,837 | | | |1822| 872,967| 29,578| 349,351 | | | |1823| 534,220| 13,050| 414,714 | | | |1824| 604,269| 53,843| 483,339 | | | |1825| 541,443| 61,908| 385,734 | | | |1826| 760,729| 68,603| 395,609 | | | |1827| 756,315| 76,875| 448,270 | 1 9 4 0 | 11,538 | |1828| 512,874| 54,999| 397,867 | 1 3 3 9 | 11,085 | |1829| 475,632| 39,344| 433,851 | 1 3 3 6 | 11,976 | |1830| 534,341| 78,099| 548,865 | 0 9 3 3 | 11,834 | |1831| 913,562|175,717| 597,568 | 0 4 2 6 | 12,559 | |1832| 378,843| 69,842| 594,155 | 0 4 2 3 | 11,420 | |1833| 326,894| 66,447| 426,460 | 0 9 2 4 | 11,457 | |1834| 708,959| 89,229| 398,832 | 0 11 2 4 | 11,928 | |1835| 528,564|203,840| 573,288 | 0 11 3 0 | 10,454 | |1836| 642,436|200,975| 642,615 | 1 0 4 0 | 9,492 | |1837|1,011,674|133,959| 427,890 | 1 0 3 9 | 8,780 | +----+---------+-------+-------------+-------------+---------+ | The Stock includes 2,200 chests of Lac-lake. | +------------------------------------------------------------+

LACCIC ACID crystallizes, has a wine-yellow colour, a sour taste, is soluble in water, alcohol, and ether. It was extracted from stick-lac by Dr. John.

LACCINE is the portion of shell-lac which is insoluble in boiling alcohol. It is brown, brittle, translucid, consisting of agglomerated pellicles, more like a resin than any thing else. It is insoluble in ether and oils. It has not been applied to any use.

LACE MANUFACTURE. The pillow-made, or bone-lace, which formerly gave occupation to multitudes of women in their own houses, has, in the progress of mechanical invention, been nearly superseded by the bobbin-net lace, manufactured at first by hand-machines, as stockings are knit upon frames, but recently by the power of water or steam. This elegant texture possesses all the strength and regularity of the old Buckingham lace, and is far superior in these respects to the point-net and warp lace, which had preceded, and in some measure paved the way for it. Bobbin-net may be said to surpass every other branch of human industry in the complex ingenuity of its machinery; one of Fisher’s spotting frames being as much beyond the most curious chronometer in multiplicity of mechanical device, as that is beyond a common roasting-jack.

The threads in bobbin-net lace form, by their intertwisting and decussation, regular hexagonal holes or meshes, of which the two opposite sides, the upper and under, are directed along the breadth of the piece, or at right angles to the selvage or border. Fig. 608. shows how, by the crossing and twisting of the threads, the regular six-sided mesh is produced, and that the texture results from the union of three separate sets of threads, of which one set proceed downwards in serpentine lines, a second set proceeds from the left to the right, and a third from the right to the left, both in slanting directions. These oblique threads twist themselves round the vertical ones, and also cross each other betwixt them, in a peculiar manner, which may be readily understood by examining the representation. In comparing bobbin-net with a common web, the perpendicular threads in the figure, which are parallel to the border, may be regarded as the warp, and the two sets of slanting threads, as the weft.

These warp threads are extended up and down, in the original mounting of the piece between a top and bottom horizontal roller or beam, of which one is called the warp beam, and the other the lace beam, because the warp and finished lace are wound upon them respectively. These straight warp threads receive their contortion from the tension of the weft threads twisted obliquely round them alternately to the right and the left hand. Were the warp threads so tightly drawn that they became inflexible, like fiddle-strings, then the lace would assume the appearance shown in fig. 609.; and although this condition does not really exist, it may serve to illustrate the structure of the web. The warp threads stand in the positions a a, a´ a´, and a´´ a´´; the one half of the weft proceeds in the direction b b, b´ b´ and b´´ b´´; and the second crosses the first by running in the direction c c, or c´ c´, towards the opposite side of the fabric. If we pursue the path of a weft thread, we find it goes on till it reaches the outermost or last warp thread, which it twists about; not once, as with the others, but twice; and then returning towards the other border, proceeds in a reverse direction. It is by this double twist, and by the return of the weft threads, that the selvage is made.

The ordinary material of bobbin-net is two cotton yarns, of from No. 180. to No. 250., twisted into one thread; but sometimes strongly twisted single yarn has been used. The beauty of the fabric depends upon the quality of the material, as well as the regularity and smallness of the meshes. The number of warp threads in a yard in breadth is from 600 to 900; which is equivalent to from 20 to 30 in an inch. The size of the holes cannot be exactly inferred from that circumstance, as it depends partly upon the oblique traction of the threads. The breadth of the pieces of bobbin-net varies from edgings of a quarter of an inch, to webs 12, or even 20 quarters, that is, 5 yards wide.

Bobbin-net lace is manufactured by means of very costly and complicated machines, called frames. The limits of this Dictionary will admit of an explanation of no more than the general principles of the manufacture. The threads for crossing and twisting round the warp, being previously gassed, that is, freed from loose fibres by singeing with gas, are wound round small pulleys, called bobbins, which are, with this view, deeply grooved in their periphery. Figs. 610, 611. exhibit the bobbin alone, and with its carriage. In the section of the bobbin a, fig. 610., the deep groove is shown in which the thread is wound. The bobbin consists of two thin discs of brass, cut out in a stamp-press, in the middle of each of which there is a hollow space c. These discs are riveted together, leaving an interval between their edge all round, in which the thread is coiled. The round hole in the centre, with the little notch at top, serves for spitting them upon a feathered rod, in order to be filled with thread by the rotation of that rod in a species of reel, called the bobbin-filling machine. Each of these bobbins (about double the size of the figure), is inserted into the vacant space G of the carriage, fig. 611. This is a small iron frame (also double the size of the figure), which, at e e, embraces the grooved border of the bobbin, and by the pressure of the spring at f, prevents it from falling out. This spring serves likewise to apply sufficient friction to the bobbin, so as to prevent it from giving off its thread at g by its rotation, unless a certain small force of traction be employed upon the thread. The curvilinear groove h h, sunk in each face or side of the carriage, has the depth shown in the section at h. This groove corresponds to the interval between the teeth of the comb, or bars of the bolt, in which each carriage is placed, and has its movement. A portion of that bolt or comb is shown at a, fig. 612. in plan, and one bar of a circular bolt machine at b, in section. If we suppose two such combs or bolts placed with the ends of the teeth opposite each other, but a little apart, to let the warp threads be stretched, in one vertical plane, between their ends or tips, we shall have an idea of the skeleton of a bobbin-net machine. One of these two combs, in the double bolt machine, has an occasional lateral movement called shogging, equal to the interval of one tooth or bolt, by which, after it has received the bobbins, with their carriages, into its teeth, it can shift that interval to the one side, and thereby get into a position to return the bobbins, with their carriages, into the next series of interstices or gates, in the other bolt. By this means the whole series of carriages receives successive side steps to the right in one bolt, and to the left in the other, so as to perform a species of countermarch, in the course of which they are made to cross and twist round about the vertical warp threads, and thus to form the meshes of the net.

The number of movements required to form a row of meshes in the double tier machine, that is, in a frame with two combs or bars, and 2 rows of bobbins, is six; that is, the whole of the carriages (with their bobbins) pass from one bar or comb to the other six times, during which passages the different divisions of bobbin and warp threads change their relative positions 12 times.

This interchange or traversing of the carriages with their bobbins, which is the most difficult thing to explain, but at the same time the most essential principle of the lace-machine, may be tolerably well understood by a careful study of fig. 613., in which the simple line | represents the bolts or teeth, the sign ● the back line of carriages, and the sign ○ the front line of carriages. H is the front comb or bolt bar, and I the back bolt bar. The former remain is always fixed or stationary, to receive the carriages as they may be presented to it by the shogging of the latter. There must be always one odd carriage at the end; the rest being in pairs.

No. 1. represents the carriages in the front comb or bar, the odd carriage being at the left end. The back line of carriages is first moved on to the back bar I, the odd carriage, as seen in No. 1., having been left behind, there being no carriage opposite to drive it over to the other comb or bar. The carriages then stand as in No. 2. The bar I now shifts to the left, as shown in No. 3.; the front carriages then go over into the back bar or comb, as is represented by No. 4. The bar I now shifts to the right, and gives the position No. 5. The front carriages are then driven over to the front bar, and leave the odd carriage on the back bar at the right end, for the same reason as before described, and the carriages stand as shown in No. 6. The bar I next shifts to the left, and the carriages stand as in No. 7. (the odd carriage being thereby on the back bar to the left.) The back carriages now come over to the front bar, and stand as in No. 8. The back bar or comb I shifts to the right as seen in No. 9., which completes the traverse. The whole carriages with their bobbins have now changed their position, as will be seen by comparing No. 9. with No. 1. The odd carriage, No. 1. ○ has advanced one step to the right, and has become one of the front tier; one of the back tier or line ● has advanced one step to the left, and has become the odd carriage; and one of the front ones ○ has gone over to the back line. The bobbins and carriages throughout the whole width of the machine have thus crossed each other’s course, and completed the mesh of net.

The carriages with their bobbins are driven a certain way from the one comb to the other, by the pressure of two long bars (one for each) placed above the level of the comb, until they come into such a position that their projecting heels or catches i i, fig. 611., are moved off by two other long flat bars below, called the locker plates, and thereby carried completely over the interval between the two combs.

There are six different systems of bobbin-net machines. 1. Heathcoate’s patent machine. 2. Brown’s traverse warp. 3. Morley’s straight bolt. 4. Clarke’s pusher principle, single tier. 5. Leaver’s machine, single tier. 6. Morley’s circular bolt. All the others are mere variations in the construction of some of their parts. It is a remarkable fact, highly honourable to the mechanical judgment of Mr. Morley of Derby, that no machines except those upon his circular bolt principle, have been found capable of working successfully by mechanical power.

The circular bolt machine (comb with curved teeth) was used by Mr. Morley, for making narrow breadths or edgings of lace immediately after its first invention, and it has been regularly used by the trade for that purpose ever since, in consequence of the inventor having declined to secure the monopoly of it to himself by patent. At that time the locker bars for driving across the carriages had only one plate or blade. A machine so mounted is now called “the single locker circular bolt.” In the year 1824, Mr. Morley added another plate to each of the locker bars, which was a great improvement on the machines for making plain net, but an obstruction to the making of narrow breadths upon them. This machine is now distinguished from the former by the term “double locker.”[31]

[31] By reading the above brief account of Bobbin-net, in connexion with the more detailed description of it in my COTTON MANUFACTURE OF GREAT BRITAIN, a tolerably clear conception of the nature of this intricate manufacture may be obtained.

A rack of lace, is a certain length of work counted perpendicularly, and contains 240 meshes or holes. Well-made lace has the meshes a little elongated in the direction of the selvage.

The term gauge, in the lace manufacture, means the number of gates, slits, or interstices, in one inch of the bolt-bar or comb; and corresponds therefore to the number of bobbins in an inch length of the double tier. Thus, when we say “gauge nine points,” we mean that there are nine gates with nine bobbins in one inch of the comb or bolt-bar. Each of such bobbins with its carriage is therefore no more than one ninth of an inch thick. The common proportion or gauge up and down the machine is 16 holes in the inch for ten bobbins transversely. Circular bolt double tier machines can turn off by steam power fully 360 racks each day of 18 hours, with a relay of superintendents.

The number of new mechanical contrivances to which this branch of manufacture has given rise, is altogether unparalleled in any other department of the arts. Since Mr. Heathcoate’s first successful patent, in 1809, a great many other patents have been granted for making lace. In the year 1811, Mr. Morley, then of Nottingham, invented his straight bolt frame, more simple in construction, better combined, and more easy in its movements, than the preceding machines; but the modest inventor did not secure it, as he might have done, by patent. The pusher machine was invented in the same year, by Samuel Mart and James Clark, also of Nottingham. The following year is remarkable in the history of the lace trade, for the invention of the circular bolt machine, by Mr. Morley--a mechanism possessing all the advantages of his straight bolt machine, without its disadvantages.

Nearly at the same time Mr. John Leaver brought forward the lever machine, conjointly with one Turton, both of New Radford, near Nottingham. About the year 1817, or 1818, Mr. Heathcoate applied the rotatory movement to the circular bolt machine, and mounted a manufactory on that plan, by mechanical power, at Tiverton, after he and his partner, Mr. Boden, had been driven from Loughborough, in 1816, by the atrocious violence of the frame-destroying Luddites.

Such has been the progress of improvement and economy in this manufacture, that the cost of labour in making a rack, which was, twenty years ago, 3_s._ 6_d._, or 42 pence, is now not more than one penny. The prices of this beautiful fabric have fallen in an equally remarkable manner. At the former period, a 24 rack piece, five quarters broad, fetched 17_l._ sterling, in the wholesale market; the same is now sold for 7_s._! The consequence is, that in lace decoration, the maid servant may now be more sumptuously arrayed than her mistress could afford to be twenty years ago.

LACQUER, is a varnish, consisting chiefly of a solution of pale shell-lac in alcohol, tinged with saffron, annotto, or other colouring matters. See VARNISH.

LACTIC ACID. (Acide Lactique, Fr.; Milchsäure, Germ.) This acid was discovered by Scheele in buttermilk, where it exists most abundantly; but it is present also in fresh milk in small quantity, and communicates to it the property of reddening litmus. Lactic acid may be detected in all the fluids of the animal body; either free or saturated with alkaline matter.

Scheele obtained this acid by evaporating the sour whey of clotted milk to an eighth part of its bulk, saturating this remainder with slaked lime, in order to throw down the subphosphate of lime held in solution, filtering the liquor, diluting it with thrice its weight of water, and precipitating the lime circumspectly, by the gradual addition of oxalic acid. He next filtered, evaporated to dryness on a water bath, and digested the residuum in strong alcohol, which dissolved the lactic acid, and left the sugar of milk. On evaporating off the alcohol, the acid was obtained. As thus procured, it requires to be purified by saturation with carbonate of lead (pure white lead), and precipitating the solution of this lactate with sulphate of zinc, not added in excess. Sulphate of lead falls, and the supernatant lactate of zinc being evaporated affords crystals, at first brown, but which become colourless on being dissolved and re-crystallized twice or thrice. If the sulphuric acid of the dissolved salt be thrown down by water of baryta, the liquid when filtered and evaporated yields a pure lactic acid, of a syrupy consistence, colourless and void of smell. It has a pungent acid taste, which it loses almost entirely when moderately diluted with water. It does not crystallize. Its salts, with the exception of those of magnesia and zinc, have a gummy appearance, and are very soluble in alcohol, unless they hold an excess of base. Lactic acid consists of 44·92 carbon; 6·55 hydrogen; 48·53 oxygen. It contains 9·92 per cent. of water. It has not hitherto been applied to any use in the arts, except by the Dutch in their old process of bleaching linen with sour milk.

LACTOMETER is the name of an instrument for estimating the quality of milk, called also a Galactometer, which see. The most convenient form of apparatus would be a series of glass tubes each about 1 inch in diameter, and 12 inches long, graduated through a space of 10 inches, to tenths of an inch, having a stop-cock at the bottom, and suspended upright in a frame. The average milk of the cow being poured in to the height of 10 inches, as soon as the cream has all separated at top, the thickness of its body may be measured by the scale; and then the skim-milk may be run off below into a hydrometer glass, in order to determine its density, or relative richness in caseous matter.

LAKES. Under this title are comprised all those colours which consist of a vegetable dye, combined by precipitation with a white earthy basis, which is usually alumina. The general method of preparation is to add to the coloured infusion a solution of common alum, or rather a solution of alum saturated with potash, especially when the infusion has been made with the aid of acids. At first only a slight precipitate falls, consisting of alumina and the colouring matter; but on adding potash, a copious precipitation ensues, of the alumina associated with the dye. When the dyes are not injured, but are rather brightened by alkalis, the above process is reversed; a decoction of the dye-stuff is made with an alkaline liquor, and when it is filtered, a solution of alum is poured into it. The third method is practicable only with substances having a great affinity for subsulphate of alumina; it consists in agitating recently precipitated alumina with the decoction of the dye.

Yellow lakes are made with a decoction of Persian or French berries, to which some potash or soda is added; into the mixture a solution of alum is to be poured as long as any precipitate falls. The precipitate must be filtered, washed, and formed into cakes, and dried. A lake may be made in the same way with quercitron, taking the precaution to purify the decoction of the dye-stuff with buttermilk or glue. After filtering the lake it may be brightened with a solution of tin. Annotto lake is formed by dissolving the dye-stuff in a weak alkaline lye, and adding alum water to the solution. Solution of tin gives this lake a lemon yellow cast; acids a reddish tint.

Red lakes.--The finest of these is carmine.

This beautiful pigment was accidentally discovered by a Franciscan monk at Pisa. He formed an extract of cochineal with salt of tartar, in order to employ it as a medicine, and obtained, on the addition of an acid to it, a fine red precipitate. Homberg published a process for preparing it, in 1656. Carmine is the colouring matter of cochineal, prepared by precipitation from a decoction of the drug. Its composition varies according to the mode of making it. The ordinary carmine is prepared with alum, and consists of carminium (see COCHINEAL), a little animal matter, alumina, and sulphuric acid. See CARMINE.

Carminated lake, called lake of Florence, Paris, or Vienna. For making this pigment, the liquor is usually employed which is decanted from the carmine process. Into this, newly precipitated alumina is put; the mixture is stirred, and heated a little, but not too much. Whenever the alumina has absorbed the colour, the mixture is allowed to settle, and the liquor is drawn off.

Sometimes alum is dissolved in the decoction of cochineal, and potash is then added, to throw down the alumina in combination with the colouring matter; but in this way an indifferent pigment is obtained. Occasionally, solution of tin is added, to brighten the dye.

A lake may be obtained from kermes, in the same way as from cochineal; but now it is seldom had recourse to.

Brazil-wood lakes.--Brazil wood is to be boiled in a proper quantity of water for 15 minutes; then, alum and solution of tin being added, the liquor is to be filtered, and a solution of potash poured in as long as it occasions a precipitate. This is separated by the filter, washed in pure water, mixed with a little gum water, and made into cakes. Or, the Brazil wood may be boiled along with a little vinegar, the decoction filtered, alum and salt of tin added, and then potash-lye poured in to precipitate the lake. For 1 pound of Brazil wood, 30 to 40 pounds of water, and from 1-1/2 to 2 pounds of alum, may be taken, in producing a deep red lake; or, the same proportions with half a pound of solution of tin. If the potash be added in excess, the tint will become violet. Cream of tartar occasions a brownish cast.

Madder lake.--A fine lake may be obtained from madder, by washing it in cold water as long as it gives out colour; then sprinkling some solution of tin over it, and setting it aside for some days. A gentle heat may also be applied. The red liquor must be then separated by the filter, and decomposed by the addition of carbonate of soda, when a fine red precipitate will be obtained. Or, the reddish brown colouring matter of a decoction of madder may be first separated by acetate of lead, and then the rose-red colour with alum. Or, madder tied up in a bag is boiled in water; to the decoction, alum is added, and then potash. The precipitate should be washed with boiling water, till it ceases to tinge it yellow; and it is then to be dried.

The following process merits a preference.

Diffuse 2 pounds of ground madder in 4 quarts of water, and after a maceration of 10 minutes, strain and squeeze the grounds in a press. Repeat this maceration, &c. twice upon the same portion of madder. It will now have a fine rose colour. It must then be mixed with 5 or 6 pounds of water and half a pound of bruised alum, and heated upon a water bath for 3 or 4 hours, with the addition of water, as it evaporates, after which the whole must be thrown upon a filter cloth. The liquor which passes is to be filtered through paper, and then precipitated by carbonate of potash. If the potash be added in three successive doses, three different lakes will be obtained, of successively diminishing beauty. The precipitates must be washed till the water comes off colourless.

Blue lakes are hardly ever prepared, as indigo, prussian blue, cobalt blue, and ultramarine, answer every purpose of blue pigments.

Green lakes are made by a mixture of yellow lakes with blue pigments; but chrome yellows mixed with blues produce almost all the requisite shades of green.

LAMINABLE is said of a metal which may be extended by passing between steel or hardened (chilled) cast-iron rollers.

For a description of metal rolling presses, see IRON and MINT; and

For a table of the relative laminability of metals, see DUCTILITY.

LAMIUM ALBUM, or the dead nettle, is said by Leuchs to afford in its leaves a greenish-yellow dye. The L. purpureum dyes a reddish-grey with salt of tin, and a greenish tint with iron liquor.

LAMPS differ so much in principle, form, and construction, as to render their description impossible, as a general subject of manufacture. In fact, the operations of the lampist, like those of the blacksmith, cabinet-maker, cooper, coppersmith, tinman, turner, &c., belong to a treatise upon handicraft trades. I shall here, however, introduce a tabular view of the relative light and economy of the lamps most generally known.

+----------+----------------------------------+------+------+-------+ | Kind | Intensity of light during | Mean |Con- | Light | | of +----+-----+-----+-----+-----+-----+ of 7 |sump- | from | | Lamps. | 1 | 2 | 3 | 4 | 5 | 6 |hours.|tion | 100 | | |hour|hours|hours|hours|hours|hours| |per | parts | | | | | | | | | |hour |of oil.| | | | | | | | | |in | | | | | | | | | | |gram- | | | | | | | | | | |mes. | | +----------+----+-----+-----+-----+-----+-----+------+------+-------+ |Mechanical| | | | | | | | | | |lamp of | | | | | | | | | | |Carcel | | | | | | |100 |42 | 238 | |Fountain | | | | | | | | | | |lamp, and | | | | | | | | | | |a chimney | | | | | | | | | | |with flat | | | | | | | | | | |wick |100 | 98 | 98 | 97 | 96 | 96 |125 |11 | 113 | |Dome ar- | | | | | | | | | | |gand |103 | 90 | 72 | 61 | 42 | 34 | 31 |26·714| 116 | |Sinumbra | | | | | | | | | | |lamp |102 | 95 | 83 | 81 | 78 | 66 | 56 |37·145| 150 | |Do. with | | | | | | | | | | |fountain | | | | | | | | | | |above |100 | 90 | 70 | 52 | 41 | 32 | 85 |43 | 197 | |Do. with | | | | | | | | | | |another | | | | | | | | | | |beak |100 | 97 | 95 | 92 | 89 | 86 | 41 |18 | 227 | |Girard’s | | | | | | | | | | |hydro- | | | | | | | | | | |static | | | | | | | | | | |lamp |101 | 96 | 84 | 81 | 76 | 70 | 63·66|34·714| 182 | |Thilo- | | | | | | | | | | |rier’s or | | | | | | | | | | |Parker’s | | | | | | | | | | |do. lamp |106 | 103 | 100 | 94 | 92 | 90 |107·66|51·143| 215 | +----------+----+-----+-----+-----+-----+-----+------+------+-------+

In the above table, for the purpose of comparing the successive degrees of intensity, 100 represents the mean intensity of light during the first hour. The quantity of oil consumed per hour is given in grammes, of 15-1/2 grains each. The last column expresses the quantity of light produced with a like consumption of oil, which was in all cases 100 grammes. See CANDLES.

The following table of M. Peclet is perhaps more instructive:--

+------------+------+--------+-------------------+----------+--------+ | Nature | In- |Consump-| Cost | Fat pro- |Cost per| | of the |tensi-|tion per+---------+---------+ducing the| hour. | | light. | ty. |hour in | per |of light | same | | | | |grammes.| kilogr. |per hour.| light. | | +------------+------+--------+---------+---------+----------+--------+ | | | |francs.| cents.|grammes.|cents.| |Mechanical | | | | | | | |lamp |100 | 42 | 1·40 | 5·8 | 42 | 5·8 | |Flat-wick | | | | | | | |mechan. do.| 12·05| 11 | 1·40 | 1·5 | 88 | 12·3 | |Hemispheri- | | | | | | | |cal dome | | | | | | | |lamp | 31·0 | 26·714 | 1·40 | 3·7 | 86·16 | 12·0 | |Sinumbra | | | | | | | |lamp | 85 | 43 | 1·40 | 6·0 | 50·58 | 7·0 | |Do. with a | | | | | | | |lateral | | | | | | | |fountain or | | | | | | | |vase | 41 | 18 | 1·40 | 2·5 | 43·90 | 6·1 | |Do. with a | | | | | | | |fountain | | | | | | | |above | 90 | 43 | 1·40 | 6·0 | 47·77 | 6·6 | |Girard’s | | | | | | | |hydrostatic | | | | | | | |lamp | 63·66| 34·71 | 1·40 | 4·8 | 54·52 | 7·6 | |Thilorier’s | | | | | | | |or Parker’s | | | | | | | |do. |107·66| 51·143 | 1·40 | 7·1 | 47·5 | 6·6 | |Candle, 6 | | | | | | | |in lb. | 10·66| 8·51 | 1·40 | 1·2 | 70·35 | 9·8 | |Do. 8 in do.| 8·74| 7·51 | 1·40 | 1·0 | 85·92 | 12·0 | |Do. 6 with | | | | | | | |smaller wick| 7·50| 7·42 | 2·40 | 1·7 | 98·93 | 23·7 | |Wax candle, | | | | | | | |5 in lb. | 13·61| 8·71 | 7·60 | 5·7 | 64·04 | 48·6 | |Sperm | | | | | | | |candle, do. | 14·40| 8·92 | 7·60 | 5·8 | 61·94 | 47·8 | |Stearine | | | | | | | |candle, do. | 14·30| 9·35 | 6·00 | 5·5 | 65·24 | 37·1 | |Coal gas |127 |136 | | 5·0 | 107 | 3·9 | | | | litres| | | litres| | |Oil gas |127 |136 do. | | 5·0 | 30 | 3·9 | +------------+------+--------+-------------------+----------+--------+

The light of the mechanical lamp is greatly over-rated relatively to that of gas. The cost of the former is at least 5 times greater than of the latter, in London.

LAMP OF DAVY consists of a common oil lamp, surmounted with a covered cylinder of wire gauze, for transmitting light to the miner without endangering the kindling of the atmosphere of fire-damp which may surround him; because carburetted hydrogen, in passing through the meshes of the cylindric cover, gets cooled by the conducting power of the metallic gauze, below the point of its accension.

The apertures in the gauze should not be more than 1-20th of an inch square. Since the fire-damp is not inflamed by ignited wire, the thickness of the wire is not of importance, but wire from 1-40th to 1-60th of an inch in diameter is the most convenient.

The cage or cylinder should be made by double joinings, the gauze being folded over in such a manner as to leave no apertures. When it is cylindrical, it should not be more than two inches in diameter; because in larger cylinders, the combustion of the fire-damp renders the top inconveniently hot; a double top is always a proper precaution, fixed 1/2 or 3/4 of an inch above the first top. See fig. 614.

The gauze cylinder should be fastened to the lamp by a screw b, fig. 615., of four or five turns, and fitted to the screw by a tight ring. All joinings in the lamp should be made with hard solder; as the security depends upon the circumstance, that no aperture exists in the apparatus, larger than in the wire-gauze.

The parts of the lamp are,

1. The brass cistern a, d, fig. 615., which contains the oil. It is pierced at one side of the centre with a vertical narrow tube, nearly filled with a wire which is recurved above, at the level of the burner, to trim the wick, by acting on the lower end of the wire e with the fingers. It is called the safety-trimmer.

2. The rim b is the screw neck for fixing on the gauze cylinder, in which the wire-gauze cover is fixed, and which is fastened to the cistern by a screw fitted to b.

3. An aperture c for supplying oil. It is fitted with a screw or a cork, and communicates with the bottom of the cistern by a tube at f. A central aperture for the wick.

4. The wire-gauze cylinder, fig. 614., which should not have less than 625 apertures to the square inch.

5. The second top, 3/4 of an inch above the first, surmounted by a brass or copper plate, to which the ring of suspension may be fixed. It is covered with a wire cap in the figure.

6. Four or six thick vertical wires, g´ g´ g´ g´, joining the cistern below with the top plate, and serving as protecting pillars round the cage. g is a screw-pin to fix the cover, so that it shall not become loosened by accident or carelessness. The oil-cistern fig. 615. is drawn upon a larger scale than fig. 614., to show its minuter parts.

When the wire-gauze safe-lamp is lighted and introduced into an atmosphere gradually mixed with fire-damp, the first effect of the fire-damp is to increase the length and size of the flame. When the inflammable gas forms so much as 1-12th of the volume of the air, the cylinder becomes filled with a feeble blue flame, while the flame of the wick appears burning brightly within the blue flame. The light of the wick augments till the fire-damp increases to 1-6th or 1-5th, when it is lost in the flame of the fire-damp, which in this case fills the cylinder with a pretty strong light. As long as any explosive mixture of gas exists in contact with the lamp, so long it will give light; and when it is extinguished, which happens whenever the foul air constitutes so much as 1-3d of the volume of the atmosphere, the air is no longer proper for respiration; for though animal life will continue where flame is extinguished, yet it is always with suffering. By fixing a coil of platinum wire above the wick, ignition may be maintained in the metal when the lamp itself is extinguished; and from this ignited wire the wick may be again rekindled, on carrying it into a less inflammable atmosphere.

“We have frequently used the lamps where the explosive mixture was so high as to heat the wire-gauze red-hot; but on examining a lamp which has been in constant use for three months, and occasionally subjected to this degree of heat, I cannot perceive that the gauze cylinder of iron wire is at all impaired. I have not, however, thought it prudent, in our present state of experience, to persist in using the lamps under such circumstances, because I have observed, that in such situations the particles of coal dust floating in the air, fire at the gas burning within the cylinder, and fly off in small luminous sparks. This appearance, I must confess, alarmed me in the first instance, but experience soon proved that it was not dangerous.

“Besides the facilities afforded by this invention to the working of coal-mines abounding in fire-damp, it has enabled the directors and superintendents to ascertain, with the utmost precision and expedition, both the presence, the quantity, and correct situation of the gas. Instead of creeping inch by inch with a candle, as is usual, along the galleries of a mine suspected to contain fire-damp, in order to ascertain its presence, we walk firmly on with the safe-lamps, and, with the utmost confidence, prove the actual state of the mine. By observing attentively the several appearances upon the flame of the lamp, in an examination of this kind, the cause of accidents which happened to the most experienced and cautious miners is completely developed; and this has hitherto been in a great measure matter of mere conjecture.

“It is not necessary that I should enlarge upon the national advantages which must necessarily result from an invention calculated to prolong our supply of mineral coal, because I think them obvious to every reflecting mind; but I cannot conclude without expressing my highest sentiments of admiration for those talents which have developed the properties, and controlled the power, of one of the most dangerous elements which human enterprise has hitherto had to encounter.”--See Letter to Sir H. Davy, in Journal of Science, vol. i. p. 302., by John Buddle, Esq., generally and justly esteemed one of the most scientific coal-miners in the kingdom.

Mr. Buddle, in a letter dated 21st August, 1835, which is published in Dr. Davy’s life of his brother Sir Humphrey, says;--

“In the evidence given in my last examination before a committee of the House of Commons, I stated that after nearly twenty years’ experience of ‘the Davy’ with from 1000 to 1500 lamps in daily use, in all the variety of circumstances incidental to coal mining, without a single accident having happened which could be attributed to a defect in its principle, or even in the rules for its practical application, as laid down by Sir Humphrey--I maintained that ‘the Davy’ approximated perfection, as nearly as any instrument of human invention could be expected to do. We have ascertained distinctly that the late explosion did not happen in that part of the mine where the Davys were used. They were all found in a perfect state after the accident--many of them in the hands of the dead bodies of the sufferers.”

LAMP-BLACK. See BLACK.

LAMPATES and LAMPIC ACID. When a spirit of wine lamp has its cotton wick surmounted with a spiral coil of platinum wire, after lighting it for a little, it may be blown out, without ceasing to burn the alcohol; for the coil continues ignited, and a current of hot vapour continues to rise, as long as the spirit lasts. This vapour was first condensed and examined by Professor Daniell, who called it lampic acid. It has a peculiar, strongly acid, burning taste, and a spec. grav. of 1·015. It possesses in an eminent degree the property of reducing certain metallic solutions; such as those of platinum, gold, and silver. The lampates may be prepared by saturating the above acid with the alkaline and earthy carbonates.

LAPIDARY, Art of. The art of the lapidary, or that of cutting, polishing, and engraving gems, was known to the ancients, many of whom have left admirable specimens of their skill. The Greeks were passionate lovers of rings and engraved stones; and the most parsimonious among the higher classes of the Cyrenians are said to have worn rings of the value of ten minæ (about 30_l._ of our money.) By far the greater part of the antique gems that have reached modern times, may be considered as so many models for forming the taste of the student of the fine arts, and for inspiring his mind with correct ideas of what is truly beautiful. With the cutting of the diamond, however, the ancients were unacquainted, and hence they wore it in its natural state. Even in the middle ages, this art was still unknown; for the four large diamonds which enrich the clasp of the imperial mantle of Charlemagne, as now preserved in Paris, are uncut, octahedral crystals. But the art of working diamonds was probably known in Hindostan and China, in very remote periods. After Louis de Berghen’s discovery, in 1476, of polishing two diamonds by their mutual attrition, all the finest diamonds were sent to Holland to be cut and polished by the Dutch artists, who long retained a superiority, now no longer admitted by the lapidaries of London and Paris.

The operation of gem cutting is abridged by two methods; 1. by cleavage; 2. by cutting off slices with a fine wire, coated with diamond powder, and fixed in the stock of a hand-saw. Diamond is the only precious stone which is cut and polished with diamond powder, soaked with olive oil, upon a mill plate of very soft steel.

Oriental rubies, sapphires, and topazes, are cut with diamond powder soaked with olive oil, on a copper wheel. The facets thus formed are afterwards polished on another copper wheel, with tripoli, tempered with water.

Emeralds, hyacinths, amethysts, garnets, agates, and other softer stones, are cut at a lead wheel, with emery and water; and are polished on a tin wheel with tripoli and water, or, still better, on a zinc wheel, with putty of tin and water.

The more tender precious stones, and even the pastes, are cut on a mill-wheel of hard wood, with emery and water; and are polished with tripoli and water, on another wheel of hard wood.

Since the lapidary employs always the same tools, whatever be the stone which he cuts or polishes, and since the wheel discs alone vary, as also the substance he uses with them, we shall describe, first of all, his apparatus, and then the manipulations for diamond-cutting, which are applicable to every species of stone.

The lapidary’s mill, or wheel, is shewn in perspective in fig. 616. It consists of a strong frame made of oak carpentry, with tenon and mortised joints, bound together with strong bolts and screw nuts. Its form is a parallelopiped of from 8 to 9 feet long, by from 6 to 7 high; and about 2 feet broad. These dimensions are large enough to contain two cutting wheels alongside of each other, as represented in the figure.

Besides the two sole bars B B, we perceive in the breadth, 5 cross bars, C, D, E, F, G. The two extreme bars C and G, are a part of the frame-work, and serve to bind it. The two cross-bars D and F, carry each in the middle of their length, a piece of wood as thick as themselves, but only 4-1/2 inches long (see fig. 617.), joined solidly by mortises and tenons with that cross bar, as well as with the one placed opposite on the other parallel face. These two pieces are called summers (lintels); the one placed at D is the upper; the one at F, the lower.

In fig. 617. this face is shewn inside, in order to explain how the mill wheel is placed and supported. The same letters point out the same objects, both in the preceding and the following figures.

In each of these summers a square hole is cut out, exactly opposite to the other; in which are adjusted by friction, a square piece of oak a a, fig. 617., whose extremities are perforated with a conical hole, which receives the two ends of the arbor H of the wheel I, and forms its socket. This square bar is adjusted at a convenient height, by a double wooden wedge b b.

The cross bar in the middle E supports the table c c, a strong plank of oak. It is pierced with two large holes whose centres coincide with the centre of the conical holes hollowed out at the end of the square pins. These holes, of about 6 inches diameter each, are intended to let the arbor pass freely through, bearing its respective wheel. (See one of these holes at I, in fig. 621. below.)

Each wheel is composed of an iron arbor H, fig. 618., of a grinding-wheel I, which differs in substance according to circumstances, as already stated, and of the pulley J, furnished with several grooves (see fig. 619.), which has a square fit upon the arbor. The arbor carries a collet d, on which are 4 iron pegs or pins that enter into the wheel to fasten it.

The wheel plate, of which the ground plan is shown at K, is hollowed out towards its centre to half its thickness; when it is in its position on the arbor, as indicated in fig. 619., a washer or ferrule of wrought iron is put over it, and secured in its place by a double wedge. In fig. 619. the wheel-plate is represented in section, that the connection of the whole parts may be seen.

A board g (see fig. 616. and fig. 624.), about 7-1/2 inches high, is fixed to the part of the frame opposite to the side at which the lapidary works, and it prevents the substances made use of in the cutting and polishing, from being thrown to a distance by the centrifugal force of the wheel-plate.

Behind this apparatus is mounted for each grinding-plate, a large wheel L (see fig. 616.), similar to a cutler’s, but placed horizontally. This wheel is grooved round its circumference to receive an endless cord or band, which passes round one of the grooves of the pulley J, fixed below the wheel-plate. Hence, on turning the fly-wheel L, the plate revolves with a velocity relative to the velocity communicated to the wheel L, and to the difference of diameter of the wheel L and the pulley J. Each wheel L, is mounted on an iron arbor, with a crank (see M, fig. 620.)

The lower pivot of that arbor h is conical, and turns in a socket fixed in the floor. The great wheel L rests on the collet i, furnished with its 4 iron pins, for securing the connection. Above the wheel an iron washer is laid, and the whole is fixed by a double wedge, which enters into the mortise l, fig. 620.

Fig. 621. exhibits a ground-plan view of all this assemblage of parts, to explain the structure of the machine. Every thing that stands above the upper summer-bar has been suppressed in this representation. Here we see the table c c; the upper summer m; the one wheel-plate l, the other having been removed to shew that the endless cord does not cross; the two large wheels L L, present in each machine, the crank bar N, seen separate in fig. 622, which serves for turning the wheel L. This bar is formed of 3 iron plates n, o; p, q; and q, r; (fig. 622.) The first is bent round at the point n, to embrace the stud s; the second p q, is of the same breadth and thickness as the first; and the third, is adjusted to the latter with a hinge joint, at the point q, where they are both turned into a circular form, to embrace the crank M. When all these pieces are connected, they are fixed at the proper lengths by the buckles or square rings t t t, which embrace these pieces, as is shown in fig. 622.

The stud s, seen in fig. 622., is fixed to the point v by a wedge-key upon the arm P, represented separately, and in perspective, in fig. 623. The labourer seizing the two upright pegs or handles x x; by the alternate forward and backward motion of his arm, he communicates the same motion to the crank rod, which transmits it to the crank of the arbor M, and impresses on that arbor, and the wheel which it bears, a rotatory movement.

Fig. 624. shows piece-meal and in perspective, a part of the lapidary’s wheel-mill. There we see the table c c, the grind-plate I, whose axis is kept in a vertical position by the two square plugs a a, fixed into the two summers by the wedges b b. On the two sides of the wheel-plate we perceive an important instrument called a dial, which serves to hold the stone during the cutting and polishing. This instrument has received lately important ameliorations, to be described in fig. 625. The lapidary holds this instrument in his hand, he rests it upon the iron pins u u fixed in the table, lest he should be affected by the velocity of the revolving wheel-plate. He loads it sometimes with weights e, e, to make it take better hold of the grinding plate.

One of the most expert lapidaries of Geneva works by means of the following improved mechanism, of his own invention, whereby he cuts and polishes the facets with extreme regularity, converting it into a true dial.

Fig. 625. shows this improvement. Each of the two jaws bears a large conchoidal cavity, into which is fitted a brass ball, which carries on its upper part a tube e, to whose extremity is fixed a dial-plate f f, engraved with several concentric circles, divided into equal parts, like the toothed-wheel cutting engine-plate, according to the number of facets to be placed in each cutting range. The tube receives with moderate friction the handle of the cement rod, which is fixed at the proper point by a thumb-screw, not shown in the figure, being concealed by the vertical limb d, about to be described.

A needle or index g, placed with a square fit on the tail of the cement rod, marks by its point the divisions on the dial plate f f. On the side m n of the jaw A, there is fixed by two screws, a limb d, forming a quadrant whose centre is supposed to be at the centre of the ball. This quadrant is divided as usual into 90 degrees, whose highest point is marked 0, and the lowest would mark about 70; for the remainder of the arc down to 90 is concealed by the jaw. The two graduated plates are used as follows:--

When the cement rod conceals zero or 0 of the limb, it is then vertical, and serves to cut the table of the brilliant; or the point opposite to it, and parallel to the table. On making it slope a little, 5 degrees for example, all the facets will now lie in the same zone, provided that the inclination be not allowed to vary. On turning round the cement rod the index g marks the divisions, so that by operating on the circle with 16 divisions, stopping for some time at each, 16 facets will have been formed, of perfect equality, and at equal distances, as soon as the revolution is completed.

Diamonds are cut at the present day in only two modes; into a rose diamond, and a brilliant. We shall therefore confine our attention to these two forms.

The rose diamond is flat beneath, like all weak stones, while the upper face rises into a dome, and is cut into facets. Most usually six facets are put on the central region, which are in the form of triangles, and unite at their summits; their bases abut upon another range of triangles, which being set in an inverse position to the preceding, present their bases to them, while their summits terminate at the sharp margin of the stone. The latter triangles leave spaces between them which are likewise cut each into two facets. By this distribution the rose diamond is cut into 24 facets; the surface of the diamond being divided into two portions, of which the upper is called the crown, and that forming the contour, beneath the former, is called dentelle (lace) by the French artists.

According to Mr. Jefferies, in his Treatise on Diamonds, the regular rose diamond is formed by inscribing a regular octagon in the centre of the table side of the stone, and bordering it by eight right-angled triangles, the bases of which correspond with the sides of the octagon; beyond these is a chain of 8 trapeziums, and another of 16 triangles. The collet side also consists of a minute central octagon, from every angle of which proceeds a ray to the edge of the girdle, forming the whole surface into 8 trapeziums, each of which is again subdivided by a salient angle (whose apex touches the girdle) into one irregular pentagon and two triangles.

To fashion a rough diamond into a brilliant, the first step is to modify the faces of the original octahedron, so that the plane formed by the junction of the two pyramids shall be an exact square, and the axis of the crystal precisely twice the length of one of the sides of the square. The octahedron being thus rectified, a section is to be made parallel to the common base or girdle, so as to cut off 5 eighteenths of the whole height from the upper pyramid, and 1 eighteenth from the lower one. The superior and larger plane thus produced is called the table, and the inferior and smaller one is called the collet; in this state it is termed a complete square table diamond. To convert it into a brilliant, two triangular facets are placed on each side of the table, thus changing it from a square to an octagon; a lozenge-shaped facet is also placed at each of the four corners of the table, and another lozenge extending lengthwise along the whole of each side of the original square of the table, which with two triangular facets set on the base of each lozenge, completes the whole number of facets on the table side of the diamond; viz. 8 lozenges, and 24 triangles. On the collet side are formed 4 irregular pentagons, alternating with as many irregular lozenges radiating from the collet as a centre, and bordered by 16 triangular facets adjoining the girdle. The brilliant being thus completed, is set with the table side uppermost, and the collet side implanted in the cavity made to receive the diamond. The brilliant is always three times as thick as the rose diamond. In France, the thickness of the brilliant is set off into two unequal portions; one third is reserved for the upper part or table of the diamond, and the remaining two thirds for the lower part or collet (culasse). The table has eight planes, and its circumference is cut into facets, of which some are triangles, and others lozenges. The collet is also cut into facets called pavillons. It is of consequence that the pavillons lie in the same order as the upper facets, and that they correspond to each other, so that the symmetry be perfect, for otherwise the play of the light would be false.

Although the rose-diamond projects bright beams of light in more extensive proportion often than the brilliant, yet the latter shows an incomparably greater play, from the difference of its cutting. In executing this, there are formed 32 faces of different figures, and inclined at different angles all round the table, on the upper side of the stone. On the collet (culasse) 24 other faces are made round a small table, which converts the culasse into a truncated pyramid. These 24 facets, like the 32 above, are differently inclined and present different figures. It is essential that the faces of the top and the bottom correspond together in sufficiently exact proportions to multiply the reflections and refractions, so as to produce the colours of the prismatic spectrum.

The other precious stones, as well as their artificial imitations, called pastes, are cut in the same fashion as the brilliant; the only difference consists in the matter constituting the wheel plates, and the grinding and polishing powders, as already stated.

In cutting the stones, they are mounted on the cement-rod B, fig. 626., whose stem is set upright in a socket placed in the middle of a sole piece at A, which receives the stem of the cement-rod. The head of the rod fills the cup of A. A melted alloy of tin and lead is poured into the head of the cement-rod, into the middle of which the stone is immediately plunged; and whenever the solder has become solid, a portion of it is pared off from the top of the diamond, to give the pyramidal form shown in the figure at B.

There is an instrument employed by the steel polishers for pieces of clock work, and by the manufacturers of watch-glasses for polishing their edges. It consists of a solid oaken table, fig. 627. The top is perforated with two holes, one for passing through the pulley and the arbor of the wheel-plate B, made either of lead or of hard wood, according to circumstances; and the other C for receiving the upper part of the arbor of the large pulley D. The upper pulley of the wheel-plate is supported by an iron prop E, fixed to the table by two wooden screws. The inferior pivots of the two pieces are supported by screw-sockets, working in an iron screw-nut sunk into the summer-bar F. The legs of the table are made longer or shorter, according as the workman chooses to stand or sit at his employment. Emery with oil is used for grinding down, and tin-putty or colcothar for polishing. The workman lays the piece on the flat of the wheel-plate with one hand, and presses it down with a lump of cork, while he turns round the handle with the other hand.

The Sapphire, Ruby, Oriental Amethyst, Oriental Emerald, and Oriental Topaz, are gems next in value and hardness to diamond; and they all consist of nearly pure alumina or clay, with a minute portion of iron as the colouring matter. The following analyses show the affinity in composition of the most precious bodies with others in little relative estimation.

+---------------+---------+---------------+------+ | |Sapphire.|Corundum Stone.|Emery.| | +---------+---------------+------+ |Alumina or clay| 98·5 | 89·50 | 86·0 | |Silica | 0·0 | 5·50 | 3·0 | |Oxide of iron | 1·0 | 1·25 | 4·0 | |Lime | 0·5 | 0·00 | 0·0 | | +---------+---------------+------+ | | 100·0 | 96·25 | 93·0 | +---------------+---------+---------------+------+

Salamstone is a variety which consists of small transparent crystals, generally six-sided prisms, of pale reddish and bluish colours. The corundum of Battagammana is frequently found in large six-sided prisms: it is commonly of a brown colour, whence it is called by the natives curundu gallé, cinnamon stone. The hair-brown and reddish-brown crystals are called adamantine spar. Sapphire and salamstone are chiefly met with in secondary repositories, as in the sand of rivers &c., accompanied by crystals and grains of octahedral iron-ore and of several species of gems. Corundum is found in imbedded crystals in a rock, consisting of indianite. Adamantine spar occurs in a sort of granite.

The finest varieties of sapphire come from Pegu, where they occur in the Capelan mountains near Syrian. Some have been found also at Hohenstein in Saxony, Bilin in Bohemia, Puy in France, and in several other countries. The red variety, the ruby, is most highly valued. Its colour is between a bright scarlet and crimson. A perfect ruby above 3-1/2 carats is more valuable than a diamond of the same weight. If it weigh one carat, it is worth 10 guineas; 2 carats, 40 guineas; 3 carats, 150 guineas; 6 carats, above 1000 guineas. A deep coloured ruby, exceeding 20 carats in weight, is generally called a carbuncle; of which 108 were said to be in the throne of the Great Mogul, weighing from 100 to 200 carats each; but this statement is probably incorrect. The largest oriental ruby known to be in the world, was brought from China to Prince Gargarin, governor of Siberia. It came afterwards into the possession of Prince Menzikoff, and constitutes now a jewel in the imperial crown of Russia.

A good blue sapphire of 10 carats is valued at 50 guineas. If it weighs 20 carats, its value is 200 guineas; but under 10 carats, the price may be estimated by multiplying the square of its weight in carats into half a guinea; thus, one of 4 carats would be worth 4² × 1/2 G. = 8 guineas. It has been said that the blue sapphire is superior in hardness to the red, but this is probably a mistake arising from confounding the corundum ruby with the spinelle ruby. A sapphire of a barbel blue colour, weighing 6 carats, was disposed of in Paris by public sale for 70_l._ sterling; and another of an indigo blue, weighing 6 carats and 3 grains, brought 60_l._; both of which sums much exceed what the preceding rule assigns, from which we may perceive how far fancy may go in such matters. The sapphire of Brasil is merely a blue tourmaline, as its specific gravity and inferior hardness show. White sapphires are sometimes so pure, that when properly cut and polished they have been passed for diamonds.

The yellow and green sapphires are much prized under the names of Oriental topaz and emerald. The specimens which exhibit all these colours associated in one stone are highly valued, as they prove the mineralogical identity of these varieties.

Besides these shades of colour, sapphires often emit a beautiful play of colours, or chatoiement, when held in different positions relative to the eye or incident light; and some likewise present star-like radiations, whence they are called star-stones or asterias; sending forth 6 or even 12 rays, that change their place with the position of the stone. This property so remarkable in certain blue sapphires, is not however peculiar to these gems. It seems to belong to transparent minerals which have a rhomboid for their nucleus, and arises from the combination of certain circumstances in their cutting and structure. Lapidaries often expose the light-blue variety of sapphire to the action of fire, in order to render it white and more brilliant; but with regard to those found at Expailly in France, fire deepens their colour.

3. Chrysoberyl, called by Haüy Cymophane, and by others Prismatic corundum, ranks next in hardness to sapphire, being 8·5 on the same scale of estimation. Its specific gravity is 3·754. It usually occurs in rounded pieces about the size of a pea, but it is also found crystallised in many forms, of which 8-sided prisms with 8-sided summits are perhaps the most frequent. Lustre vitreous; colour asparagus green, passing into greenish-white and olive-green. It shows a bluish opalescence, a light undulating as it were in the stone, when viewed in certain directions; which property constitutes its chief attraction to the jeweller. When polished, it has been sometimes mistaken for a yellow diamond; and from its hardness and lustre is considerably valued. Good specimens of it are very rare. It has been found only in the alluvial deposits of rivers, along with other species of gems. Thus it occurs in Brasil, along with diamonds and prismatic topaz; also in Ceylon. Its constituents are, alumina 68·66; glucina 16·00; silica 6·00; protoxide of iron 4·7; oxide of titanium 2·66; moisture 0·66, according to Seybert’s analysis of a specimen from Brasil. It is difficultly but perfectly fusible before the blowpipe, with borax and salt of phosphorus. In composition it differs entirely from sapphire, or the rhombohedral corundum.

4. Spinelle Ruby, called Dodecahedral corundum by some mineralogists, and Balas ruby by lapidaries. Its hardness is 8. Specific gravity 3·523. Its fundamental form is the hexahedron, but it occurs crystallized in many secondary forms: octahedrons, tetrahedrons and rhombohedrons. Fracture conchoidal; lustre vitreous; colour red, passing into blue and green, yellow, brown and black; and sometimes it is nearly white. Red spinelle consists of, alumina 74·5; silica 15·5; magnesia 8·25; oxide of iron 1·5; lime 0·75. Vauquelin discovered 6·18 per cent. of chromic acid in the red spinelle. The red varieties exposed to heat, become black and opaque; on cooling they appear first green, then almost colourless, but at last resume their red colour. Pleonaste is a variety which yields a deep green globule with borax.

Crystals of spinelle from Ceylon have been observed imbedded in limestone, mixed with mica, or in rocks containing adularia, which seem to have belonged to a primitive district. Other varieties like the pleonaste occur in the drusy cavities of rocks ejected by Vesuvius. Crystals of it are often found in diluvial and alluvial sand and gravel, along with true sapphires, pyramidal zircon, and other gems, as also with octahedral iron ore, in Ceylon. Blue and pearl-gray varieties occur in Südermannland in Sweden, imbedded in granular limestone. Pleonaste is met with also in the diluvial sands of Ceylon. Clear and finely coloured specimens of spinelle are highly prized as ornamental stones. When the weight of a good spinelle exceeds 4 carats, it is said to be valued at half the price of a diamond of the same weight. M. Brard has seen one at Paris, which weighed 215 grains.

5. Zircon or Hyacinth. Its fundamental form is an isosceles 4-sided pyramid; and the secondary forms have all a pyramidal character. Fracture conchoidal, uneven; lustre more or less perfectly adamantine; colours, red, brown, yellow, gray, green, white; which with the exception of some red tints, are not bright. Hardness 7·5. Specific gravity 4·5. Zircon and hyacinth consist, according to Klaproth, of almost exactly the same constituents; namely, zirconia 70; silica 25; oxide of iron 5. In the white zirconia there is less iron and more silica. Before the blowpipe the hyacinth loses its colour, but does not melt. The brighter zircons are often worked up into a brilliant form, for ornamenting watch cases. As a gem, hyacinth has no high value. It has been often confounded with other stones, but its very great specific gravity makes it to be readily recognized.

6. Topaz. The fundamental form is a scalene 4-sided pyramid; but the secondary forms have a prismatic character; and are frequently observed in oblique 4-sided prisms, acuminated by 4 planes. The lateral planes of the prism are longitudinally striated. Fracture conchoidal, uneven; lustre vitreous; colours, white, yellow, green, blue, generally of pale shades. Hardness 8; specific gravity 3·5. Prismatic topaz consists, according to Berzelius, of alumina 57·45; silica 34·24; fluoric acid 7·75. In a strong heat the faces of crystallization, but not those of cleavage, are covered with small blisters, which however immediately crack. With borax, it melts slowly into a transparent glass. Its powder colours the tincture of violets green. Those crystals which possess different faces of crystallization on opposite ends, acquire the opposite electricities on being heated. By friction, it acquires positive electricity.

Most perfect crystals of topaz have been found in Siberia, of green, blue, and white colours, along with beryl, in the Uralian and Altai mountains, as also in Kamschatka; in Brazil, where they generally occur in loose crystals, and pebble forms of bright yellow colours; and in Mucla in Asia Minor, in pale straw-yellow regular crystals. They are also met with in the granitic detritus of Cairngorm in Aberdeenshire. The blue varieties are absurdly called oriental aquamarine by lapidaries. If exposed to heat, the Saxon topaz loses its colour and becomes white; the deep yellow Brazilian varieties assume a pale pink hue; and are then sometimes mistaken for spinelle, to which, however, they are somewhat inferior in hardness. Topaz is also distinguishable by its double refractive property. Tavernier mentions a topaz, in the possession of the Great Mogul, which weighed 157 carats, and cost 20,000_l._ sterling. There is a specimen in the museum of natural history at Paris which weighs 4 ounces 2 gros.

Topazes are not scarce enough to be much valued by the lapidary.

7. Emerald and Beryl, are described in their alphabetical places. Emerald loses its lustre by candle-light; but as it appears to most advantage when in the company of diamonds, it is frequently surrounded with brilliants, and occasionally with pearls. Beryl is the aqua-marine of the jewellers, and has very little estimation among lapidaries.

8. Garnet. See this stone in its alphabetical place.

9. Chrysolite, called Peridot by Haüy; probably the topaz of the ancients, as our topaz was their chrysolite. It is the softest of the precious stones, being scratched by quartz and the file. It refracts double.

10. Quartz, including, as sub-species, Amethyst, Rock-crystal, Rose-quartz, Prase or Chrysoprase, and several varieties of calcedony, as Cat’s eye, Plasma, Chrysoprase, Onyx, Sardonyx, &c. Lustre vitreous, inclining sometimes to resinous; colours, very various; fracture conchoidal; hardness, 7; specific gravity, 2·69.

11. Opal, or uncleavable quartz. Fracture, conchoidal; lustre, vitreous or resinous; colours, white, yellow, red, brown, green, gray. Lively play of light; hardness, 5·5 to 6·5; specific gravity, 2·091. It occurs in small kidney-shaped and stalactitic shapes, and large tuberose concretions. The phenomena of the play of colours in precious opal has not been satisfactorily explained. It seems to be connected with the regular structure of the mineral. Hydrophane, or oculis mundi, is a variety of opal without transparency, but acquiring it when immersed in water, or in any transparent fluid. Precious opal was found by Klaproth to consist of silica, 90; water, 10; which is a very curious combination. Hungary has been long the only locality of precious opal, where it occurs near Caschau, along with common and semi-opal, in a kind of porphyry. Fine varieties have, however, been lately discovered in the Faroe islands; and most beautiful ones, sometimes quite transparent, near Gracias a Dios, in the province of Honduras, America. The red and yellow bright coloured varieties of fire-opal are found near Zimapan, in Mexico. Precious opal, when fashioned for a gem, is generally cut with a convex surface; and if large, pure, and exhibiting a bright play of colours, is of considerable value. In modern times, fine opals of moderate bulk have been frequently sold at the price of diamonds of equal size; the Turks being particularly fond of them. The estimation in which opal was held by the ancients is hardly credible. They called it Paideros, or Child beautiful as love. Nonius, the Roman senator, preferred banishment to parting with his favourite opal, which was coveted by Mark Antony. Opal which appears quite red when held against the light, is called girasol by the French; a name also given to the sapphire or corundum asterias or star-stone.

12. Turquois, or Calaite. Mineral turquois, occurs massive; fine-grained impalpable; fracture conchoidal; colour, between a blue and a green, soft, and rather bright; opaque; hardness, 6; spec. grav. 2·83 to 3·0. Its constituents are, alumina, 73; oxide of copper, 4·5; oxide of iron, 4; water, 18; according to Dr. John. But by Berzelius, it consists of phosphate of alumina and lime, silica, oxides of copper and iron, with a little water. It has been found only in the neighbourhood of Nichabour in the Khorassan, in Persia; and is very highly prized as an ornamental stone in that country. There is a totally different kind of turquois, called bone turquois, which seems to be phosphate of lime coloured with oxide of copper. When the oriental stone is cut and polished, it forms a pleasing gem of inferior value. Malachite, or mountain green, a compact carbonate of copper, has been substituted sometimes for turquois, but their shades are different. Malachite yields a green streak, and turquois a white one.

13. Lapis lazuli, is of little value, on account of its softness.

LEAD. (Plomb, Fr.; Blei, Germ.) This is one of the metals most antiently known, being mentioned in the books of Moses. It has a gray blue colour, with a bright metallic lustre when newly cut, but it becomes soon tarnished and earthy looking in the air. Its texture is close, without perceptible cleavage or appearance of structure; the specific gravity of common lead is 11·352; but of the pure metal, from 11·38 to 11·44. It is very malleable and ductile, but soft and destitute of elasticity; fusible at 612° Fahr., by Crighton, at 634° by Kupfer, and crystallizable on cooling, into octahedrons implanted into each other so as to form an assemblage of four-sided pyramids.

There are four oxides of lead. 1. The suboxide of a grayish blue colour, which forms a kind of crust upon a plate of lead long exposed to the air. It is procured in a perfect state by calcining oxalate of lead in a retort; the dark gray powder which remains is the pure suboxide. 2. The protoxide is obtained by exposing melted lead to the atmosphere, or, more readily, by expelling the acid from the nitrate of lead by heat in a platinum crucible. It is yellow, and was at one time prepared as a pigment by calcining lead; but is now superseded by the chromate of this metal. Litharge is merely this oxide in the form of small spangles, from having undergone fusion; it is more or less contaminated with iron, copper, and sometimes a little silver. It contains likewise some carbonic acid. The above oxide consists of 104 of metal, and 8 of oxygen, its prime equivalent being 112, upon the hydrogen scale; and it is the base of all the salts of lead. 3. The plumbeous suroxide of Berzelius, the sesquioxide of some British chemists, is the well-known pigment called RED LEAD or minium. It consists of 100 parts of metal and 10 of oxygen. 4. The plumbic suroxide of Berzelius, or the peroxide of the British chemists, is obtained by putting red lead in chlorine water, or in dilute nitric acid. It is of a dark brown, almost black colour, which gives out oxygen when heated, and becomes yellow oxide. It kindles sulphur when triturated with it. This oxide is used by the analytical chemist to separate, by condensation, the sulphurous acid existing in a gaseous mixture.

Among the ores of lead some have a metallic aspect; are black in substance, as well as when pulverized; others have a stony appearance, and are variously coloured, with usually a vitreous or greasy lustre. The specific gravity of the latter ores is always less than 5. The whole of them, excepting the chloride, become more or less speedily black, with sulphuretted hydrogen or with hydrosulphurets; and are easily reduced to the metallic state upon charcoal, with a flux of carbonate of soda, after they have been properly roasted. They diffuse a whitish or yellowish powder over the charcoal, which, according to the manner in which the flame of the blowpipe is directed upon it, becomes yellow or red; thus indicating the two characteristic colours of the oxides of lead.

We shall not enter here into the controversy concerning the existence of native lead, which has been handled at length by M. Brongniart in the Dictionnaire des Sciences Naturelles, article Plomb, Mineralogie.

The lead ores most interesting to the arts are:--

1. Galena, sulphuret of lead. This ore has the metallic lustre of lead with a crystalline structure derivable from the cube. When heated cautiously at the blowpipe it is decomposed, the sulphur flies off, and the lead is left alone in fusion; but if the heat be continued, the coloured surface of the charcoal indicates the conversion of the lead into its oxides. Galena is a compound of lead and sulphur, in equivalent proportions, and therefore consists, in 100 parts, of 86-2/3 of metal, and 13-1/3 of sulphur, with which numbers the analysis of the galena of Clausthal by Westrumb exactly agrees. Its specific gravity, when pure, is 7·56. Its colour is blackish gray, without any shade of red, and its powder is black; characters which distinguish it from blende or sulphuret of zinc. Its structure in mass is lamellar, passing sometimes into the fibrous or granular, and even compact. It is brittle. The specular galena, so called from its brightly polished aspect, is remarkable for forming the slickensides of Derbyshire--thin seams, which explode with a loud noise when accidentally scratched in the mine.

The argentiferous galena has in general all the external characters of pure galena. The proportions of silver vary from one-fifth part of the whole, as at Tarnowitz, in Silesia, to three parts in ten thousand, as in the ore called by the German miners Weisgültigerz; but it must be observed, that whenever this lead ore contains above 5 per cent. of silver, several other metals are associated with it. The mean proportion of silver in galena, or that which makes it be considered practically as an argentiferous ore, because the silver may be profitably extracted, is about two parts in the thousand. See SILVER. The above rich silver ores were first observed in the Freyberg mines, called Himmelsfürst and Beschertglück, combined with sulphuret of antimony; but they have been noticed since in the Hartz, in Mexico, and several other places.

The antimonial galena (Bournonite) exhales at the blowpipe the odour peculiar to antimony, and coats the charcoal with a powder partly white and partly red. It usually contains some arsenic.

2. The Seleniuret of lead, resembles galena, but its tint is bluer. Its chemical characters are the only ones which can be depended on for distinguishing it. At the blowpipe, it exhales a very perceptible smell of putrid radishes. Nitric acid liberates the selenium. When heated in a tube, oxide of selenium of a carmine red rises along with selenic acid, white and deliquescent. The specific gravity of this ore varies from 6·8 to 7·69.

3. Native minium or red lead, has an earthy aspect, of a lively and nearly pure red colour, but sometimes inclining to orange. It occurs pulverulent, and also compact, with a fracture somewhat lamellar. When heated at the blowpipe upon charcoal, it is readily reduced to metallic lead. Its specific gravity varies from 4·6 to 8·9. This ore is rare.

4. Plomb-gomme. This lead ore, as singular in appearance as in composition, is of a dirty brownish or orange-yellow, and occurs under the form of globular, or gum-like concretions. It has also the lustre and translucency of gum; with somewhat of a pearly aspect at times. It is harder than fluor spar. It consists of oxide of lead, 40; alumina, 37; water, 18·8; foreign matters and loss, 4·06; in 100. Hitherto it has been found only at Huelgoët, near Poullaouen, in Brittany, covering with its tears or small concretions the ores of white lead and galena which compose the veins of that lead mine.

5. White lead, carbonate of lead. This ore in its purest state, is colourless and transparent like glass, with an adamantine lustre. It may be recognized by the following characters:--

Its specific gravity is from 6 to 6·7; it dissolves with more or less ease, and with effervescence, in nitric acid; becomes immediately black by the action of sulphuretted hydrogen, and melts on charcoal before the blowpipe into a button of lead. According to Klaproth, the carbonate of Leadhills contains 82 parts of oxide of lead, and 16 of carbonic acid, in 98 parts. This mineral is tender, scarcely scratches calc-spar, and breaks easily with a waved conchoidal fracture. It possesses the double refracting property in a very high degree; the double image being very visible on looking through the flat faces of the prismatic crystals. Its crystalline forms are very numerous, and are referrible to the octahedron, and the pyramidal prism.

6. Vitreous lead, or sulphate of lead. This mineral closely resembles carbonate of lead; so that the external characters are inadequate to distinguish the two. But the following are sufficient. When pure, it has the same transparency and lustre. It does not effervesce with nitric acid; it is but feebly blackened by sulphuretted hydrogen; it first decrepitates and then melts before the blowpipe into a transparent glass, which becomes milky as it cools. By the combined action of heat and charcoal, it passes first into a red pulverulent oxide, and then into metallic lead. It consists, according to Klaproth, of 71 oxide of lead, 25 sulphuric acid, 2 water, and 1 iron. That specimen was from Anglesea; the Wanlockhead mineral is free from iron. The prevailing form of crystallization is the rectangular octahedron, whose angles and edges are variously modified. The sulphato-carbonate, and sulphato tri-carbonate of lead, now called Leadhillite, are rare minerals which belong to this head.

7. Phosphate of lead.--This, like all the combinations of lead with an acid, exhibits no metallic lustre, but a variety of colours. Before the blowpipe, upon charcoal, it melts into a globule externally crystalline, which, by a continuance of the heat, with the addition of iron and boracic acid, affords metallic lead. Its constituents are 80 oxide of lead, 18 phosphoric acid, and 1·6 muriatic acid, according to Klaproth’s analysis of the mineral from Wanlockhead. The constant presence of muriatic acid in the various specimens examined is a remarkable circumstance. The crystalline forms are derived from an obtuse rhomboid. Phosphate of lead is a little harder than white lead; it is easily scratched, and its powder is always gray. Its specific gravity is 6·9. It has a vitreous lustre, somewhat adamantine. Its lamellar texture is not very distinct; its fracture is wavy, and it is easily frangible. The phosphoric and arsenic acids being, according to M. Mitscherlich, isomorphous bodies, may replace each other in chemical combinations in every proportion, so that the phosphate of lead may include any proportion, from the smallest fraction of arsenic acid, to the smallest fraction of phosphoric acid, thus graduating indefinitely into arseniate of lead. The yellowish variety indicates, for the most part, the presence of arsenic acid.

8. Muriate of lead. Horn-lead, or murio-carbonate.--This ore has a pale yellow colour, is reducible to metallic lead by the agency of soda, and is not altered by the hydrosulphurets. At the blowpipe it melts first into a pale yellow transparent globule, with salt of phosphorus and oxide of copper; and it manifests the presence of muriatic acid by a bluish flame. It is fragile, tender, softer than carbonate of lead, and is sometimes almost colourless, with an adamantine lustre. Spec. grav. 606. Its constituents, according to Berzelius, are, lead, 25·84; oxide of lead, 57·07; carbonate of lead, 6·25; chlorine, 8·84; silica, 1·46; water, 0·54; in 100 parts. The carbonate is an accidental ingredient, not being in equivalent proportion. Klaproth found chlorine, 13·67; lead, 39·98; oxide of lead, 22·57; carbonate of lead, 23·78.

9. Arseniate of lead.--Its colour of a pretty pure yellow, bordering slightly on the greenish, and its property of exhaling by the joint action of fire and charcoal a very distinct arsenical odour, are the only characters which distinguish this ore from the phosphate of lead. The form of the arseniate of lead when it is crystallized, is a prism with six faces, of the same dimensions as that of phosphate of lead. When pure, it is reducible upon charcoal, before the blowpipe, into metallic lead, with the copious exhalation of arsenical fumes; but only in part, and leaving a crystalline globule, when it contains any phosphate of lead. The arseniate of lead is tender, friable, sometimes even pulverulent, and of specific gravity 5·04. That of Johann-Georgenstadt consists, according to Rose, of oxide of lead 77·5; arsenic acid 12·5; phosphoric acid 7·5, and muriatic acid 1·5.

10. Red lead, or Chromate of lead.--This mineral is too rare to require consideration in the present work.

11. Plomb vauquelinite. Chromate of lead and copper.

12. Yellow lead. Molybdate of lead.

13. Tungstate of lead.

Having thus enumerated the several species of lead ore, we may remark, that galena is the only one which occurs in sufficiently great masses to become the object of mining and metallurgy. This mineral is found in small quantity among the crystalline primitive rocks, as granite. It is however among the oldest talc-schists and clay slates, that it usually occurs. But galena is much more abundant among the transition rocks, being its principal locality, where it exists in interrupted beds, masses, and more rarely in veins. The blackish transition limestone is of all rocks that which contains most galena; as at Pierreville in Normandy; at Clausthal, Zellerfeldt, and most mines of the Harz; at Fahlun, in Sweden; in Derbyshire and Northumberland, &c. In the transition graywacke of the south of Scotland, the galena mines of Leadhills occur. The galena of the primitive formations contains more silver than that of the calcareous.

The principal lead mines at present worked in the world, are the following: 1. Poullaouen and Huelgoët near Carhaix in France, department of Finisterre, being veins of galena, which traverse a clay slate resting upon granite. They have been known for upwards of three centuries; the workings penetrate to a depth of upwards of 300 yards, and in 1816 furnished 500 tons of lead per annum, out of which 1034 pounds avoirdupois of silver were extracted. 2. At Villeforte and Viallaz, department of the Lozère, are galena mines said to produce 100 tons of lead per annum, with 400 kilogrammes of silver (880 libs. avoird.). 3. At Pezey and Macot, to the east of Moutiers in Savoy, a galena mine exists in talc-schist, which has produced annually 200 tons of lead, and about 600 kilogrammes of silver (1320 libs avoird.). 4. The mine of Vedrin, near Namur in the Low Countries, is opened upon a vein of galena, traversing compact limestone of a transition district; it has furnished 200 tons of lead, from which 385 pounds avoird. of silver were extracted. 5. In Saxony the galena mines are so rich in silver as to make the lead be almost overlooked. They are enumerated under silver ores. 6. The lead mines of the Harz, have been likewise considered as silver ores. 7. Those of Bleyberg in the Eifel are in the same predicament. 8. The galena mines of Bleyberg and Villach in Carinthia, in compact limestone. 9. In Bohemia, to the south-west of Prague. 10. The mines of Joachimsthal, and Bleystadt, on the southern slope of the Erzgebirge, produce argentiferous galena. 11. There are numerous lead mines in Spain, the most important being in the granite hills of Linarès, upon the southern slope of the Sierra Morena, and in the district of the small town of Canjagar. Sometimes enormous masses of galena are extracted from the mines of Linarès. There are also mines of galena in Catalonia, Grenada, Murcia, and Almeria, the ore of the last locality being generally poor in silver. 12. The lead mines of Sweden are very argentiferous, and worked chiefly with a view to the silver. 13. The lead mines of Daouria are numerous and rich, lying in a transition limestone, which rests on primitive rocks; their lead is neglected on account of the silver.

14. Of all the countries in the world, Great Britain is that which annually produces the greatest quantity of lead. According to M. Villefosse, in his Richesse Minerale, published in 1810, we had furnished every year 12,500 tons of lead, whilst all the rest of Europe taken together, did not produce so much; but from more recent documents, that estimate seems to have been too low. Mr. Taylor has rated the total product of the United Kingdom per annum at 31,900 tons, a quantity fully 2-1/2 times greater than the estimate of Villefosse (see Conybeare and Phillips’ Geology, p. 354). Mr. Taylor distributes this product among the different districts as follows:--

Tons. Wales, (Flintshire and Denbighshire) 7,500 Scotland, (in transition graywacke) 2,800 Durham, Cumberland, and Yorkshire, (in carboniferous lime) 19,000 Derbyshire, (probably in carboniferous lime) 1,000 Shropshire 800 Devon and Cornwall, (transition and primitive rocks) 800 ------ Total 31,900

We thus see that Cumberland, and the adjacent parts of the counties of Durham and York, furnish of themselves nearly three-fifths of the total product. Derbyshire was formerly much more productive. In Cornwall and Devonshire, the lead ore is found in veins in killas, a clay-slate passing into greywacke. In North Wales and the adjacent counties, as well as in Cumberland and Derbyshire, the lead occurs in the carboniferous limestone.

The English lead-miners distinguish three different kinds of deposits of lead ore; rake-veins, pipe-veins, and flat-veins. The English word vein corresponds to the French term filon; but miners make use of it indifferently in England and France, to indicate all the deposits of this ore, adding an epithet to distinguish the different forms; thus, rake veins are true veins in the geological acceptation of the word vein; pipe-veins are masses usually very narrow, and of oblong shape, most frequently parallel to the plane of the rocky strata; and flat-veins are small beds of ores interposed in the middle of these strata.

Rake-veins are the most common form in which lead ore occurs in Cumberland. They are in general narrower in the sandstone which covers the limestone, than in the calcareous beds. A thickness of less than a foot in the former, becomes suddenly 3 or 4 feet in the latter; in the rich vein of Hudgillburn, the thickness is 17 feet in the Great limestone, while it does not exceed 3 feet in the overlying Watersill or sandstone. This influence exercised on the veins by the nature of the enclosing rock, is instructive; it determines at the same time almost uniformly their richness in lead ore, an observation similar to what has been made in other countries, especially in the veins of Kongsberg in Norway. The Cumberland veins are constantly richer, the more powerful they are, in the portions which traverse the calcareous rocks, than in the beds of sandstone, and more particularly the schistose rocks. It is rare in the rock called plate (a solid slaty clay) for the vein to include any ore; it is commonly filled with a species of potter’s earth. The upper calcareous beds are also in general more productive than the lower ones. In most of these mines, the veins were not worked till lately below the fifth calcareous bed (the four-fathom limestone), which is 307 yards beneath the millstone-grit; and as the first limestone stratum is 108 yards beneath it, it follows that the thickness of the part of the ground where the veins are rich in lead does not in general exceed 200 yards. It appears however that veins have been mined in the neighbourhood of Alston Moor, downwards to the eleventh calcareous stratum, or Tyne bottom limestone, which is 418 yards under the millstone-grit of the coal formation, immediately above the whin-sill; and that they have been followed above the first limestone stratum, as high as the grindstone sill, which is only 83 yards below the same stratum of millstone-grit; so that in the total thickness of the plumbiferous formation there is more than 336 yards. It has been asserted that lead veins have been traced even further down, into the Memerby scar limestone; but they have not been mined.

The greatest enrichment of a vein takes place commonly in the points where its two sides, being not far asunder, belong to the same rock; and its impoverishment occurs when one side is calcareous and the other a schistose clay. The minerals which most frequently accompany the galena, are carbonate of lime, fluate of lime, sulphate of baryta, quartz, and pyrites.

The pipe-veins (amas in French), are seldom of great length; but some have a considerable width; their composition being somewhat similar to that of the rake-veins. They meet commonly in the neighbourhood of the two systems, sometimes being in evident communication together; they are occasionally barren; but when a wide pipe-vein is metalliferous, it is said to be very productive.

The flat veins, or strata veins, seem to be nothing else than expansions of the matter of the vein between the planes of the strata; and contain the same ores as the veins in their vicinity. When they are metalliferous, they are worked along with the adjacent rake vein; and are productive to only a certain distance from that vein, unless they get enriched by crossing a rake vein. Some examples have been adduced of advantageous workings in flat veins in the great limestone of Cumberland, particularly in the mines of Coalcleugh and Nenthead. The rake veins, however, furnish the greater part of the lead which Cumberland and the adjacent counties send every year into the market. Mr. Forster gives a list of 165 lead mines, which have been formerly, or are now, worked in that district of the kingdom.

The metalliferous limestone occupies, in Derbyshire, a length of about 25 miles from north-west to south-east, under a very variable breadth, which towards the south, amounts to 25 miles. Castleton to the north, Buxton to the north-west, and Matlock to the south-east, lie nearly upon its limits. It is surrounded on almost all sides by the millstone grit which covers it, and which is, in its turn, covered by the coal strata. The nature of the rocks beneath the limestone is not known. In Cumberland the metalliferous limestone includes a bed of trap, designated under the name of whinsill. In Derbyshire the trap is much more abundant, and it is thrice interposed between the limestone. These two rocks constitute of themselves the whole mineral mass, through a thickness of about 550 yards, measuring from the millstone grit; only in the upper portion, that is near the millstone grit, there is a pretty considerable thickness of argillo-calcareous schists.

Four great bodies or beds of limestone are distinguishable, which alternate with three masses of trap, called toadstone. The lead veins exist in the calcareous strata, but disappear at the limits of the toadstone. It has now been ascertained however that they recur in the limestone underneath.

Treatment of the Ores of Lead.

The mechanical operations performed upon the lead ores in Great Britain, to bring them to the degree of purity necessary for their metallurgic treatment, may be divided into three classes, whose objects are,--

1. The sorting and cleansing of the ores;

2. The grinding;

3. The washing, properly so called.

The apparatus subservient to the first objects are sieves, running buddles, and gratings. The large sieves employed in Derbyshire for sorting the ore at the mouth of the mine, into coarse and fine pieces, is a wire gauze of iron; its meshes are square, and an inch long in each side. There is a lighter sieve of wire gauze, similar to the preceding, for washing the mud from the ore, by agitating the fragments in a tub filled with water. But in Derbyshire, instead of using this sieve, the pieces of ore are sometimes merely stirred about with a shovel, in a trough filled with water. This is called a standing buddle; a most defective plan.

The running buddle serves at once to sort and cleanse the ore. It consists of a plane surface made of slabs or planks, very slightly inclined forwards, and provided behind and on the sides with upright ledges, the back one having a notch to admit a stream of water. The ore is merely stirred about with a shovel, and exposed on the slope to the stream. For this apparatus, formerly the only one used at the mines of Alston Moor, the following has been substituted, called the grate. It is a grid, composed of square bars of iron, an inch thick, by from 24 to 32 inches long, placed horizontally, and parallelly to each other, an inch apart. There is a wooden canal above the grate, which conducts a stream of water over its middle; and an inclined plane is set beneath it, which leads to a hemispherical basin, about 24 inches inches in diameter, for collecting the metallic powder washed out of the ore.

The apparatus subservient to grinding the ore are,--

1. The bucker, or beater, formed of a cast-iron plate, 3 inches square, with a socket in its upper surface, for receiving a wooden handle. In the neighbourhood of Alston Moor, crushing cylinders have been substituted for the beating bucker; but even now, in Derbyshire, buckers are generally employed for breaking the pieces of mixed ore, called knock-stone-stuff.

At the mines of this county, the knocker’s workshop, or striking floor, is provided either with a strong stool, or a wall 3 feet high, beyond which there is a flat area 4 feet broad, and a little raised behind. On this area, bounded, except in front, by small walls, the ore to be bruised is placed. On the stool, or wall, a very hard stone slab, or cast-iron plate is laid, 7 feet long, 7 inches broad, and 1-1/2 inches thick, called a knock-stone. The workmen seated before it, break the pieces of mixed ore, called bowse in Derbyshire, with the bucker.

Crushing machines are in general use at Alston Moor, to break the mingled ores, which they perform with great economy of time and labour. They have been employed there for nearly forty years.

This machine is composed of one pair of fluted cylinders, x x, fig. 628., and of two pairs of smooth cylinders z z, z z, which serve altogether for crushing the ore. The two cylinders of each of the three pairs turn simultaneously in an inverse direction, by means of two toothed wheels, as at m, fig. 629., upon the shaft of every cylinder, which work by pairs in one another. The motion is given by a single water wheel, of which the circle a a a represents the outer circumference. One of the fluted cylinders is placed in the prolongation of the shaft of this wheel, which carries besides a cast-iron toothed wheel, geered with the toothed wheels e e, fixed upon the ends of two of the smooth cylinders. Above the fluted cylinders, there is a hopper, which discharges down between them, by means of a particular mechanism, the ore brought forward by the waggons A. These waggons advance upon a railway, stop above the hopper, and empty their contents into it through a trap-hole, which opens outwardly in the middle of their bottom. Below the hopper there is a small bucket called a shoe, into which the ore is shaken down, and which throws it without ceasing upon the cylinders, in consequence of the constant jolts given it by a crank-rod i (fig. 629.) attached to it, and moved by the teeth of the wheel m. The shoe is so regulated, that too much ore can never fall upon the cylinders, and obstruct their movement. A small stream of water is likewise led into the shoe, which spreads over the cylinders, and prevents them from growing hot. The ore, after passing between the fluted rollers, falls upon the inclined planes N, N, which turn it over to one or other of the pairs of smooth rolls.

These are the essential parts of this machine; they are made of iron, and the smooth ones are case-hardened, or chilled, by being cast in iron moulds. The gudgeons of both kinds move in brass bushes fixed upon iron supports k, made fast by bolts to the strong wood-work basis of the whole machine. Each of the horizontal bars has an oblong slot, at one of whose ends is solidly fixed one of the plummer-blocks or bearers of one of the cylinders f, and in the rest of the slot the plummer-block of the other cylinder g slides; a construction which permits the two cylinders to come into contact, or to recede to such a distance from each other, as circumstances may require. The movable cylinder is approximated to the fixed one by means of the iron levers X X, which carry at their ends the weights P, and rest upon wedges M, which may be slidden upon the inclined plane N. These wedges then press the iron bar O, and make it approach the movable cylinder by advancing the plummer-block which supports its axis. When matters are so arranged, should a very large or hard piece present itself to one of the pairs of cylinders, one of the rollers would move away, and let the piece pass without doing injury to the mechanism.

Besides the three pairs of cylinders which constitute essentially each crushing machine, there is sometimes a fourth, which serves to crush the ore when not in large fragments, for example, the chats and cuttings (the moderately rich and poorer pieces), produced by the first sifting with the brake sieve, to be presently described. The cylinders composing that accessory piece, which, on account of their ordinary use, are called chats-rollers, are smooth, and similar to the rollers z z, and Z´ Z´. The one of them is usually placed upon the prolongation of the shaft of the water-wheel, of the side opposite to the principal machine; and the other, which is placed alongside, receives its motion from the first, by means of toothed wheel-work.

The stamp mill is employed in concurrence with the crushing cylinders. It serves particularly to pulverize those ores whose gangue is too hard to yield readily to the rollers, and also those which being already pulverized to a certain degree, require to be ground still more finely. The stamps employed in the neighbourhood of Alston Moor are moved by water wheels. They are similar to those described under TIN.

Proper sifting or jigging apparatus.--The hand sieve made of iron wire meshes, of various sizes, is shaken with the two hands in a tub of water, the ore vat, being held sometimes horizontally, and at others in an inclined position. This sieve is now in general use only for the cuttings that have passed through the grating, and which though not poor enough to require finer grinding, are too poor for the brake sieve. When the workman has collected a sufficient quantity of these smaller pieces, he puts them in his round hand sieve, shakes it in the ore vat with much rapidity and a dexterous toss, till he has separated the very poor portions called cuttings, from the mingled parts called chats, as well as from the pure ore. He then removes the first two qualities, with a sheet-iron scraper called a limp, and he finds beneath them, a certain portion of ore which he reckons to be pure.

The brake sieve is rectangular, as well as the cistern in which it is agitated. The meshes are made of strong iron wire, three-eighths of an inch square. This sieve is suspended at the extremity of a forked lever, or brake, turning upon an axis by means of two upright arms about 5 feet long, which are pierced with holes for connecting them with bolts or pins, both to the sieve-frame and to the ends of the two branches of the lever. These two arms are made of wrought iron, but the lever is made of wood; as it receives the jolt. A child placed near its end, by the action of leaping, jerks it smartly up and down, so as to shake effectually the sieve suspended at the other extremity. Each jolt not only makes the fine parts pass through the meshes, but changes the relative position of those which remain on the wires, bringing the purer and heavier pieces eventually to the bottom. The mingled fragments of galena, and the stony substances called chats lie above them; while the poor and light pieces called cuttings, are at top. These are first scraped off by the limp, next the mixed lumps, or chats, and lastly the pure ore, which is carried to the bing heap. The cuttings are handed to a particular class of workmen, who by a new sifting, divide them into mere stones, or second cuttings, and into mixed ore analogous to chats.

The poor ore, called chats, is carried to a crushing machine, where it is bruised between two cylinders appropriated to this purpose under the name of chats rollers; after which it is sifted afresh. During the sifting many parcels of small ore and stony substances pass through the sieve, and accumulate at the bottom of the cistern. When it is two-thirds filled, water is run slowly over it, and the sediment called smitham is taken out, and piled up in heaps. More being put into the tub, a child lifts up the smitham, and lays it on the sieve, which retains still on its meshes the layer of fine ore. The sifter now agitates in the water nearly as at first, from time to time removing with the limp the lighter matters as they come to the surface; which being fit for washing only in boxes, are called buddler’s offal, and and are thrown into the buddle hole.

Mr. Petherick, the manager of Lanescot and the Fowey Consol mines, has contrived an ingenious jigging machine, in which a series of 8 sieves are fixed in a stationary circular frame, connected with a plunger or piston working in a hollow cylinder, whereby a body of water is alternately forced up through the crushed ore in the sieves, and then left to descend. In this way of operating, the indiscriminate or premature passage of the finer pulverulent matter through the meshes is avoided, because a regulated stream of water is made to traverse the particles up and down. This mode has proved profitable in washing the copper ores of the above mentioned copper mines.

Proper washing apparatus.--For washing the ore after sifting it, the running buddle already described is employed, along with several chests or buddles of other kinds.

1. The trunk buddle is a species of German chest (see METALLURGY and TIN) composed of two parts; of a cistern or box into which a stream of water flows, and of a large tank with a smooth level bottom. The ore to be trunked being placed in the box, the workman furnished with a shovel bent up at its sides, agitates it, and removes from time to time the coarser portions; while the smaller are swept off by the water and deposited upon the level area.

2. The stirring buddle, or chest for freeing the schlamms or slimy stuff from clay, is analogous to the German chests, and consists of two parts; namely, 1. a trough which receives a stream of water through a plug hole, which is tempered at pleasure, to admit a greater or less current; 2. a settling tank with a horizontal bottom. The metallic slime being first floated in the water of the trough, then flows out and is deposited in the tank; the purest parts falling first near the beginning of the run.

3. The nicking buddle is analogous to the tables called dormantes or jumelles by the French miners. See METALLURGY. They have at their upper end a cross canal or spout, equal in length to the breadth of the table, with a plug hole in its middle for admitting the water. Alongside of this channel there is a slightly inclined plank, called nicking board, corresponding to the head of the twin table, and there is a nearly level plane below. The operation consists in spreading a thin layer of the slime upon the nicking board, and in running over its surface a slender sheet of water, which in its progress is subdivided into rills, which gradually carry off the muddy matters, and strew them over the lower flat surface of the tank, in the order of their density.

4. The dolly tub or rinsing bucket, fig. 630., has an upright shaft, which bears the vane or dolly A B, turned by the winch handle. This apparatus serves to bring into a state of suspension in water, the fine ore, already nearly pure; the separation of the metallic particles from the earthy ones by repose, being promoted by the sides of the tub being struck frequently during the subsidence.

5. Slime pits.--In the several operations of cleansing ores from mud, in grinding, and washing, where a stream of water is used, it is impossible to prevent some of the finely attenuated portions of the galena called sludge, floating in the water, from being carried off with it. Slime pits or labyrinths, called buddle holes in Derbyshire, are employed to collect that matter, by receiving the water to settle, at a little distance from the place of agitation.

These basins or reservoirs are about 20 feet in diameter, and from 24 to 40 inches deep. Here the suspended ore is deposited, and nothing but clear water is allowed to escape.

The workmen employed in the mechanical preparation of the ores, are paid, in Cumberland, by the piece, and not by day’s wages. A certain quantity of crude ore is delivered to them, and their work is valued by the bing, a measure containing 14 cwt. of ore ready for smelting. The price varies according to the richness of the ore. Certain qualities are washed at the rate of two and sixpence, or three shillings the bing; while others are worth at least ten shillings. The richness of the ore varies from 2 to 20 bings of galena per shift of ore; the shift corresponding to 8 waggons load.

1. The cleansing and sorting of the ores are well performed in Cumberland. These operations seem however to be inferior to the cleansing on the grid steps, grilles à gradin, of Saxony (see METALLURGY), an apparatus which in cleaning the ores, has the advantage of grouping them in lots of different qualities and dimensions.

2. The breaking or bruising by means of the crushing machine, is much more expeditious than the Derbyshire process by buckers; for the machine introduces not only great economy into the breaking operation, but it likewise diminishes considerably the loss of galena; for stamped ores may be often subjected to the action of the cylinders without waste, while a portion of them would have been lost with the water that runs from the stamp mill. The use of these rollers may therefore be considered as one of the happiest innovations hitherto made in the mechanical preparation of ores.

3. The brake sieves appear to be preferable to the hand ones.

4. The system of washing used in Cumberland differs essentially from that of Brittany. The slime pits are constructed with much less care than in France and Germany. They never present, as in these countries, those long windings backwards and forwards, whence they have been called labyrinths; probably because the last deposits, which are washed with profit in France and Germany, could not be so in Cumberland. There is reason to believe, however, that the introduction of brake tables, (tables à secousses, see METALLURGY) would enable deposits to be saved, which at present run to waste in England.

5. From what we have now said about the system of washing, and the basins of deposit or settling cisterns, it may be inferred that the operation followed in Cumberland is more expeditious than that used in Brittany, but it furnishes less pure ores, and occasions more considerable waste; a fact sufficiently obvious, since the refuse stuff at Poullaouen is often resumed, and profitably subjected to a new preparation. We cannot however venture to blame this method, because in England, fuel being cheap, and labour dear, there may possibly be more advantage in smelting an ore somewhat impure, and in losing a little galena, than in multiplying the number of washing processes.

6. Lastly, the dolly tub ought to be adopted in all the establishments where the galena is mixed with much blende (sulphuret of zinc); for schlich (metallic slime) which appears very clean to the eye, gives off a considerable quantity of blende by means of the dolly tub. While the vane is rapidly whirled, the sludge is gradually let down into the revolving water, till the quantity is sufficiently great. Whenever the ore is thoroughly disseminated in the liquid, the dolly is withdrawn. The workmen then strike on the sides of the tub for a considerable time, with mallets or wooden billets, to make the slime fall fast to the bottom. The lighter portions, consisting almost entirely of refuse matter, fall only after the knocking has ceased; the water is now run away; then the very poor slime upon the top of the deposit is skimmed off; while the pure ore found at the bottom of the tub is lifted out, and laid on the bingstead. In this way the blende, which always accompanies galena in a greater or smaller quantity, is well separated.

Smelting of lead ores.--The lead ores of Derbyshire and the north of England were antiently smelted in very rude furnaces, or boles, urged by the natural force of the wind, and were therefore placed on the summits or western slopes of the highest hills. More recently these furnaces were replaced by blast hearths, resembling smith’s forges, but larger; and were blown by strong bellows, moved by men or water-wheels. The principal operation of smelting is at present always executed in Derbyshire in reverberatory furnaces, and at Alston Moor in furnaces similar to those known in France by the name of Scotch furnaces. Before entering into the detail of the founding processes, we shall give a description of the furnaces essential for both the smelting and accessory Operations.

1. The reverberatory furnace called cupola, now exclusively used in Derbyshire for the smelting of lead ores, was imported thither from Wales, about the year 1747, by a company of Quakers. The first establishment in this county was built at Kalstedge, in the district of Ashover.

In the works where the construction of these furnaces is most improved, they are interiorly 8 feet long by 6 wide in the middle, and two feet high at the centre. The fire, placed at one of the extremities, is separated from the body of the furnace by a body of masonry, called the fire-bridge, which is two feet thick, leaving only from 14 to 18 inches between its upper surface and the vault. From this, the highest point, the vault gradually sinks towards the further end, where it stands only 6 inches above the sole. At this extremity of the furnace, there are two openings separated by a triangular prism of fire-stone, which lead to a flue, a foot and a half wide, and 10 feet long, which is recurved towards the top, and runs into an upright chimney 55 feet high. The above flue is covered with stone slabs, carefully jointed with fire-clay, which may be removed when the deposit formed under them (which is apt to melt), requires to be cleaned out. One of the sides of the furnace is called the labourers’ side. It has a door for throwing coal upon the fire-grate, besides three small apertures each about 6 inches square. These are closed with movable plates of cast iron, which are taken off when the working requires a freer circulation of air, or for the stirring up of the materials upon the hearth. On the opposite side, called the working side, there are five apertures; namely, three equal and opposite to those just described, shutting in like manner with cast iron plates, and beneath them two other openings, one of which is for running out the lead, and another for the scoriæ. The ash pit is also on this side, covered with a little water, and so disposed as that the grate-bars may be easily cleared from the cinder slag.

The hearth of the furnace is composed of the reverberatory furnace slags, to which a proper shape has been given by beating them with a strong iron rake, before their entire solidification. On the labourers’ side, this hearth rises nearly to the surface of the three openings, and falls towards the working side, so as to be 18 inches below the middle aperture. In this point, the lowest of the furnace, there is a tap-hole, through which the lead is run off into a large iron boiler (lea-pan), placed in a recess left outside in the masonry. From that lowest point, the sole gradually rises in all directions, forming thus an inside basin, into which the lead runs down as it is smelted. At the usual level of the metal bath, there is on the working side, at the end furthest from the fire, an aperture for letting off the slag.

In the middle of the arched roof there is a small aperture, called the crown-hole, which is covered up during the working with a thick cast iron plate. Above this aperture a large wooden or iron hopper stands, leading beneath into an iron cylinder, through which the contents of the hopper may fall into the furnace when a trap or valve is opened.

2. The roasting furnace.--This was introduced about 30 years ago, in the neighbourhood of Alston Moor, for roasting the ore intended to pass through the Scotch furnace, a process which greatly facilitates that operation. Since its first establishment it has successively received considerable improvements.

Figs. 631, 632, 633., represent the cupola furnace at the Marquess of Westminster’s lead smelting works, two miles from Holywell. The hearth is hollowed out below the middle door of the furnace; it slopes from the back and ends towards this basin. The distance from the lowest point of this concavity up to the sill of the door, is usually 24 inches, but it is sometimes a little less, according to the quality of the ores to be smelted. This furnace has no hole for running off the slag, above the level of the top hole for the lead i, like the smelting furnace of Lea, near Matlock. A single chimney stalk serves for all the establishments; and receives all the flues of the various roasting and reducing furnaces. Fig. 633. gives an idea of the distribution of these flues. a a a, &c. are the furnaces; b, the flues, 18 inches square; these lead from each furnace to the principal conduit c, which is 5 feet deep by 2-1/2 wide; d is 6 feet deep by 3 wide; e is a round chamber 15 feet in diameter; f is a conduit 7 feet high by 5 wide; g another, 6 feet high by 3 wide. The chimney at h has a diameter at bottom of 30 feet, at top of 12 feet, including the thickness of its sides, forming a truncated cone 100 feet high; whose base stands upon a hill a little way from the furnaces, and 62 feet above their level.

a, figs. 631, 632., is the grate; b, the door of the fire-place; c, the fire-bridge; d, the arched roof; e, the hearth; f f f, &c., the working doors; g g, flues running into one conduit, which leads to the subterranean condensing chamber, e, and thence to the general chimney; h, a hopper-shaped opening in the top of the furnace, for supplying it with materials.

This magnificent structure is not destined solely for the reduction of the ores, but for dissipating all the vapours which might prove noxious to the health of the work-people and to vegetation.

The ores smelted at Holywell are very refractory galenas, mixed with blende, calamine, pyrites, carbonate of lime, &c., but without any fluate of lime. They serve mutually as fluxes to one another. The coal is of inferior quality. The sole of each furnace is formed of slags obtained in the smelting, and they are all of one kind. In constructing it, 7 or 8 tons of these slags are first of all thrown upon the brick area of the hearth; are made to melt by a brisk fire, and in their stiffening state, as they cool, they permit the bottom to be sloped and hollowed into the desired shape. Four workmen, two at each side of the furnace, perform this task.

The ordinary charge of ore for one smelting operation is 20 cwt., and it is introduced through the hopper; see COPPER, fig. 304. An assistant placed at the back doors spreads it equally over the whole hearth with a rake; the furnace being meanwhile heated only with the declining fire of a preceding operation. No regular fire is made during the first two hours, but a gentle heat merely is kept up by throwing one or two shovelfuls of small coal upon the grate from time to time. All the doors are closed, and the register-plate of the chimney is lowered.

The outer basin in front of the furnace is at this time filled with the lead derived from a former process, the metal being covered with slags. A rectangular slit above the tap hole is left open, and remains so during the whole time of the operation, unless the lead should rise in the interior basin above the level of that orifice; in which case a little mound must be raised before it.

The two doors in front furthest from the fire being soon opened, the head-smelter throws in through them, upon the sole of the furnace, the slags swimming upon the bath of lead, and a little while afterwards he opens the tap-hole, and runs off the metallic lead reduced from these slags. At the same time his assistant turns over the ore with his paddle, through the back doors. These being again closed, while the above two front doors are open, the smelter throws a shovelful of small coal or coak cinder upon the lead bath, and works the whole together, turning over the ore with the paddle or iron oar. About three quarters of an hour after the commencement of the operation, he throws back upon the sole of the hearth the fresh slags which then float upon the bath of the outer basin, and which are mixed with coaly matter. He next turns over these slags, as well as the ore with the paddle, and shuts all the doors. At this time the smelter runs off the lead into the pig-moulds.

The assistant now turns over the ore once more through the back doors. A little more than an hour after the operation began, a quantity of lead proceeding from the slag last remelted, is run off by the tap; being usually in such quantity as to fill one half of the outer basin. Both the workmen then turn over the ore with the paddles, at the several doors of the furnace. Its interior is at this time of a dull red heat; the roasting being carried on rather by the combustion of the sulphurous ingredients, than by the action of the small quantity of coal in the grate. The smelter, after shutting the front doors, with the exception of that next the fire-bridge, lifts off the fresh slags lying upon the surface of the outside bath, drains them, and throws them back into the furnace.

An hour and a half after the commencement, the lead begins to ooze out in small quantities from the ore; but little should be suffered to flow before two hours have expired. About this time the two workmen open all the doors, and turn over the ore, each at his own side of the furnace. An hour and three quarters after the beginning, there are few vapours in the furnace, its temperature being very moderate. No more lead is then seen to flow upon the sloping hearth. A little coal being thrown into the grate to raise the heat slightly, the workmen turn over the ore, and then close all the doors.

At the end of two hours, the first fire or roasting being completed, and the doors shut, the register is to be lifted a little, and coal thrown upon the grate to give the second fire, which lasts during 25 minutes. When the doors are now opened, the inside of the furnace is of a pretty vivid red, and the lead flows down from every side towards the inner basin. The smelter with his rake or paddle pushes the slags upon that basin back towards the upper part of the sole, and his assistant spreads them uniformly over the surface through the back doors. The smelter next throws in by his middle door, a few shovelfuls of quicklime upon the lead bath. The assistant meanwhile, for a quarter of an hour, works the ore and the slags together through the three back doors, and then spreads them out, while the smelter pushes the slags from the surface of the inner basin back to the upper parts of the sole. The doors being now left open for a little, while the interior remains in repose, the metallic lead, which had been pushed back with the slags, flows down into the basin. This occasional cooling of the furnace is thought to be necessary for the better separation of the products, especially of the slags from the lead bath.

In a short time the workmen resume their rakes, and turn over the slags along with the ore. Three hours after the commencement, a little more fuel is put into the grate, merely to keep up a moderate heat of the furnace during the paddling. After three hours and ten minutes, the grate being charged with fuel for the third fire, the register is completely opened, the doors are all shut, and the furnace is left in this state for three quarters of an hour. In nearly four hours from the commencement, all the doors being opened, the assistant levels the surfaces with his rake, in order to favour the descent of any drops of lead; and then spreads the slags, which are pushed back towards him by the smelter. The latter now throws in a fresh quantity of lime, with the view not merely of covering the lead bath and preventing its oxidizement, but of rendering the slags less fluid.

Ten minutes after the third fire is completed, the smelter puts a new charge of fuel in the grate, and shuts the doors of the furnace to give it the fourth fire. In four hours and forty minutes from the commencement, this fire being finished, the doors are opened, the smelter pierces the tap-hole to discharge the lead into the outer basin, and throws some quicklime upon the slags in the inner basin. He then pushes the slags thus dried up towards the upper part of the hearth, and his assistant rakes them out by the back doors.

The whole operation of a smelting shift takes about four hours and a half, or at most five hours, in which four periods may be distinguished.

1. The first fire for roasting the ores, requires very moderate firing, and lasts two hours.

2. The second fire, or the smelting, requires a higher heat, with shut doors; at the end the slags are dried up with lime, and the furnace is also allowed to cool a little.

3, 4. The last two periods, or the third and fourth fires, are likewise two smeltings or foundings, and differ from the first only in requiring a higher temperature. The heat is greatest in the last. The form and dimensions of the furnace are calculated to cause a uniform distribution of heat over the whole surface of the hearth. Sometimes billets of green wood are plunged into the metallic lead of the outer basin, causing an ebullition which favours the separation of the slags, and consequently the production of a purer lead; but no more metallic metal is obtained.

Ten cwts. of coal are consumed at Holywell in smelting one ton of the lead-ore schlich or sludge; but at Grassington, near Skipton in Yorkshire, with a similar furnace worked with a slower heat, the operation taking from seven hours to seven hours and a half, instead of five, only 7-1/2 cwts. of coal are consumed. But here the ores are less refractory, have the benefit of fluor spar as a flux, and are more exhausted of their metal, being smelted upon a less sloping hearth.

Theory of the above operations.--At Holywell, Grassington, and in Cornwall, the result of the first graduated roasting heat, is a mixture of undecomposed sulphuret of lead, with sulphate and oxide of lead, in proportions which vary with the degree of care bestowed upon the process. After the roasting, the heat is raised to convert the sludge into a pasty mass; in which the oxide and sulphate re-act upon the sulphuret, so as to produce a sub-sulphuret, which parts with the metal by liquation. The cooling of the furnace facilitates the liquation every time that the sub-sulphuret is formed, and the ore has passed by increase of temperature from the pasty into the liquid state. Cooling brings back the sludge to the pasty condition, and is therefore necessary for the due separation of the different bodies. The drying up of the thin slags by lime is intended to liberate the oxide of lead, and allow it to re-act upon any sulphuret which may have resisted roasting or decomposition. It is also useful as a thickener, in a mechanical point of view. The iron of the tools, which wear away very fast, is also serviceable in reducing the sulphuret of lead. The small coal added along with the lime at Grassington, and also sometimes at Holywell, aids in reducing the oxide of lead, and in transforming the sulphate into sulphuret.

3. The smelting furnace or ore hearth.--This furnace, called by the French écossais, is from 22 to 24 inches in height and 1 foot by 1-1/2 in area inside; but its horizontal section, always rectangular, varies much in its dimensions at different levels, as shown in fig. 634.

The hearth and the sides are of cast iron; the sole-plate A B is also of cast iron, 2-1/2 inches thick, having on its back and two sides an upright ledge, A C, 2-1/2 inches thick, and 4-1/4 high. In front of the hearth there is another cast iron plate M N, called the work-stone, surrounded on every side excepting towards the sole of the furnace, by a ledge one inch in thickness and height. The plate slopes from behind forwards, and its posterior ledge, which is about 4-1/2 inches above the surface of the hearth, is separated from it by a void space q, which is filled with a mixture of bone ash and galena, both in fine powder, moistened and pressed down together. The melted lead cannot penetrate into this body, but after filling the basin at the bottom of the furnace, flows naturally out by the gutter (nearly an inch deep) through a groove in the work-stone; and then passes into a cauldron of reception P, styled the melting-pot, placed below the front edge of the work-stone.

The posterior ledge of the sole is surmounted by a piece of cast iron C D, called the back-stone, 28 inches long, and 6-1/2 high; on which the tuyère or blast-pipe is placed. It supports another piece of cast iron E, called pipe-stone, scooped out at its under part, in the middle of its length, for the passage of the tuyère. This piece advances 2 inches into the interior of the furnace, the back wall of which is finally crowned by another piece of cast iron E H, called also back-stone.

On the ledges of the two sides of the sole, are placed two pieces of cast iron, called bearers, each of which is 5 inches in breadth and height, and 26 inches long. They advance an inch or two above the posterior and highest edge of the work-stone, and contribute effectually to fix it solidly in its place. These bearers support, through the intervention of several ranges of fire-bricks, a piece of cast iron called a fore-stone, which has the same dimensions as the piece called the back-stone, on which the base of the blowing-machine rests. This piece is in contact, at each of its extremities, with another mass of cast iron, 6 inches cube, called the key-stone, supported on the masonry. Lastly, the void spaces left between the two key-stones and the back part of the furnace are filled up with two masses of cast iron exactly like the key-stones.

The front of the furnace is open for about 12 inches from the lower part of the front cross-piece called fore-stone, up to the superior part of the work-stone. It is through this opening that the smelter operates.

The gaseous products of the combustion, on escaping from this ore-hearth, are frequently made to pass through a long flue, sloped very slightly upwards, in which they deposit all the particles of ore that they may have swept along; these flues, whose length is sometimes more than 100 yards, are usually 5 feet high and 3 feet wide in the inside, and always terminate in a chimney stalk. The matters deposited near the commencement of the flue require to be washed; but not the other dusty deposits. The whole may then be carried back to the roasting furnace, to be calcined and re-agglutinated, or introduced without any preparation into the slag-hearth.

4. Figs. 635, 636. represent a slag-hearth, the fourneau à manche (elbow furnace) of the French, and the krummofen (crooked furnace) of the Germans; such as is used at Alston Moor, in Cumberland, for the reduction of the lead-slag. It resembles the Scotch furnace. The shaft is a parallelopiped, whose base is 26 inches by 22 in area inside, and whose height is 3 feet; the sole-plate a, of cast iron, slopes slightly down to the basin of reception, or the fore-hearth b. Upon both of the long sides of the sole-plate there are cast iron beams, called bearers C C, of great strength, which support the side walls built of a coarse grained sand-stone, as well as the cast-iron plate d (fore-stone), which forms the front of the shaft. This stands 7 inches off from the sole-plate, leaving an empty space between them. The back side is made of cast iron, from the sole-plate to the horizontal tuyère in its middle; but above this point it is made of sand-stone. The tuyère is from 1-1/5 to 2 inches in diameter. In front of the fore-hearth b, a cistern e, is placed, through which water continually flows, so that the slags which spontaneously overflow the fore-hearth may become inflated and shattered, whereby the lead disseminated through them may be readily separated by washing. The lead itself flows from the fore-hearth b, through an orifice, into an iron pot f, which is kept hot over a fire. The metal obtained from this slag-hearth is much less pure than that extracted directly from the ore.

The whole bottom of the furnace is filled to a height of 17 inches, that is, to within 2 or 3 inches of the tuyère, with the rubbish of coke reduced to coarse powder and beat strongly down. At each smelting shift, this bed must be made anew, and the interior of the furnace above the tuyère repaired, with the exception of the front, consisting of cast iron. In advance of the furnace there is a basin of reception, which is also filled with coke rubbish. Farther off is a pit, full of water, replenished by a cold stream, which incessantly runs in through a pipe. The scoriæ, in flowing out of the furnace, pass over the coke bed in the basin of reception, and then fall into the water, whose coolness makes them fly into small pieces, after which they are easily washed, so as to separate the lead that may be entangled among them.

These furnaces are urged, in general, by wooden bellows; fig. 637. But at the smelting works of Lea, near Matlock, the blowing-machine consists of two casks, which move upon horizontal axes. Each of these casks is divided into two equal parts by a fixed plane that passes through its axis, and is filled with water to a certain height. The water of one side communicates with that of the other by an opening in the lower part of the division. Each cask possesses a movement of oscillation, produced by a rod attached to a crank of a bucket-wheel. At each demi-oscillation, one of the compartments, being in communication with the external air, is filled; whilst the other, on the contrary, communicates with the nozzle, and supplies wind to the furnace.

5. Refining or cupellation furnace. See SILVER.

6. Smelting by the reverberatory furnace, is adopted exclusively in Derbyshire, and in some works at Alston-moor. The charge in the hopper consists commonly of 16 cwt., each weighing 120 lbs. avoirdupois, composed of an intimate mixture of 5, 6, 7 or even 8 kinds of ore, derived from different mines, and prepared in different ways. The proportions of the mixture are determined by experience, and are of great consequence to the success of the work.

The ore is rather in the form of grains than of a fine schlich; it is sometimes very pure, and affords 75 per cent.; but usually it is mixed up with a large proportion of carbonate and fluate of lime; and its product varies from 65 to 23 per cent.

After scraping the slaggy matters out of the furnace, a fresh smelting shift is introduced at an interval of a few minutes; and thus, by means of two alternate workmen, who relieve each other every seven or eight hours, the weekly operations continue without interruption. The average product in lead of the reverberatory furnaces in Derbyshire, during several years, has been 66 per cent. of the ore. Very fine ore has, however, afforded 76.

7. Smelting of the drawn slag, on the slag-mill hearth.--The black slag of the reverberatory furnace is broken by hammers into small pieces, and mixed in proper proportions with the coal cinders that fall through the grate of the reverberatory fire. The leaden matts that float on the surface of the bath, and the dust deposited in the chimney, are added, along with some poor ore containing a gangue of fluor spar and limestone, which had been put aside during the mechanical preparation. With such a mixture, the slag-hearth, already described, figs. 635, 636., is charged. By the action of heat and coal, the lead is revived, the earthy matters flow into very liquid scoriæ, and the whole is made to pass across the body of fire into a basin of reception placed beneath. The scoriæ are thickened by throwing quicklime upon them, and they are then raked away. At the end of the operation the lead is cast into pigs or ingots of a peculiar form. This is called slag-lead. It is harder, more sonorous than the lead obtained from the reverberatory furnace, and is preferred for the manufacture of minium, lead shot, and some other purposes.

8. Treatment of lead ores by the Scotch furnace, or ore-hearth.--This furnace is generally employed in the counties of Northumberland, Cumberland, and Durham, for the smelting of lead ores, which were formerly carried to them without any preparation, but now they are exposed to a preliminary calcination. The roasted ore yields in the Scotch furnace a more considerable product than the crude ore, because it forms in the furnace a more porous mass, and at the same time it works drier, to use the founders’ expression; that is, it allows the stream of air impelled by the bellows to diffuse itself more completely across the matters contained in the furnace.

The charge of the roasting furnace, figs. 631, 632, 633., is from 9 to 11 cwt. of ore, put into the furnace without any addition. Three such shifts are usually passed through in eight hours. The fire should be urged in such a manner as to produce constantly a dense smoke, without letting any part of the ore melt and form a slag; an accident which would obstruct the principal end of the process, which is to burn off the sulphur and antimony, and to expel the carbonic acid of the carbonate of lead. The ore must be frequently turned over, by moving it from the bridge to the other end and back again. To prevent the ore from running into masses as it cools, it is made to fall out of the furnace into a pit full of water, placed below one of the lateral doors.

Smelting of the lead ores in the Scotch furnace.--When a smelting shift has been finished in the Scotch furnace, a portion of the ore, called browse, remains in a semi-reduced state, mixed with coke and cinders. It is found of more advantage to preserve the browse for beginning the following operation, than to take raw or even roasted ore. To set the furnace in action, the interior of it is filled with peats, cut into the form of bricks. The peats towards the posterior part are heaped up without order, but those near the front are piled up with care in the form of a wall. A kindled peat is now placed before the nozzle of the bellows, which are made to blow, and the blast spreads the combustion rapidly through the whole mass. To increase the heat, and to render the fire more steady and durable, a few shovelfuls of coals are thrown over the turf. A certain quantity of the browse is to be next introduced; and then (or sometimes before all the browse is put in) the greater part of the matters contained in the furnace is drawn over on the work-stone, by means of a large rake called a gowelock; the refuse of the ore called gray slag, which a skilful smelter knows by its shining more than the browse, is taken off with a shovel, and thrown to the right hand into a corner outside of the furnace. The browse left on the work-stone is to be now thrown back into the furnace, with the addition of a little coal, if necessary. If the browse be not well cleaned from the slag, which is perceived by the whole mass being in a soft state, and shewing a tendency to fuse, quicklime must be added, which by its affinity for the argillaceous, siliceous, and ferruginous substances, dries up the materials, as the smelters say, and gives to the earthy parts the property of concreting into lumps or balls; but if, on the other hand, the siliceous, argillaceous, or ferruginous parts contained in the ore be too refractory, lime is also to be added, but in smaller quantity, which, by rendering them more fusible, communicates the property of concreting into balls. These lumps, called gray slag, contain from one-tenth to one-fifteenth of the lead which was present in the ore. They must be smelted afterwards at a higher temperature in the slag hearth, to extract their lead. After the browse has been thrown back into the furnace, as has been said, a few shovelfuls of ore are to be strewed over it; but before doing this, and after removing the scoriæ, there must be always placed before the tuyère half a peat, a substance which, being extremely porous and combustible, not only hinders any thing from entering the nozzle of the bellows, but spreads the blast through all the vacant parts of the furnace. After an interval of from 10 to 15 minutes, according to circumstances, the materials in the furnace are drawn afresh upon the work-stone, and the gray slag is removed by the rake. Another peat being placed before the tuyère, and coal and quicklime being introduced in suitable proportions, the browse is thrown back into the furnace, a fresh portion of ore is charged above it, and left in the furnace for the above mentioned time.

This mode of working, continued for 14 or 15 hours, forms what is called a smelting shift; in which time from 20 to 40 cwt. of lead, and even more, are produced.

By this process the purest part of the lead, as well as the silver, are sweated out, as it were, from the materials, with which they are mixed, without any thing entering into fusion except these two metals in the state of alloy. It is probable that the moderate temperature employed in the Scotch furnace is the main cause of the purity of the lead which it yields.

9. Smelting of the scoriæ of the Scotch furnace on the slag hearth.--Before putting fire to the slag hearth already described, figs. 635, 636., its empty space is to be filled with peats, and a lighted one being placed before the tuyère, the bellows are made to play. A layer of coke is to be now thrown upon the burning peats, and as soon as the heat is sufficiently high, a layer of the gray slag is to be introduced, or of any other scoriæ that are to be reduced. From time to time, as the fit moment arrives, alternate strata of coke and slag are to be added. In this operation, though the slag and the lead are brought to a state of perfect fluidity; the metal gets separated by filtering down through the bed of peat cinders, which the slag cannot do on account of its viscidity. Whenever that coke bed becomes covered with fluid slag, the workman makes a hole in it, of about an inch diameter, by means of a kneed poker; and runs it off by this orifice, as it cannot sink down into the hard rammed cinders, which fill the basin of reception. The slag flows over it in a glowing stream into the pit filled with water, where it gets granulated and ready for washing.

When lead is obtained from galena without the addition of combustible matter, we have an example on the great scale, of the mutual decomposition of the oxides and sulphates formed during the roasting heat, by the still undecomposed galena, especially when this action is facilitated by working up and skilfully mingling the various matters, as happens in the reverberatory and Scotch furnaces. It is therefore the sulphuret of lead itself which serves as the agent of reduction in regard to the oxide and sulphate, when little or no charcoal has been added. Sometimes, however, towards the end of the operation in the reverberatory hearth, it becomes necessary to throw in some wood or charcoal, because the oxidizement having become too complete, there does not remain a sufficient body of sulphuret of lead to effect the decompositions and reductions just mentioned, and therefore it is requisite to regenerate some galena by means of carbonaceous matter, which immediately converts the sulphate of lead into the sulphuret. The sulphur and oxygen are eventually all separated in the form of sulphurous acid. Roasted galena contains sometimes no less than 77 per cent. of sulphate of lead.

At Viconago in the Valais, the process of smelting lead ore in the reverberatory furnace with the addition of iron, as practised at Vienne on the Isère, was introduced; but the difficulty of procuring a sufficient supply of old iron has led to an interesting modification.

On the hearth of the reverberatory furnace, 10 quintals of moderately rich ore are spread; these are heated temperately for some time, and stirred about to promote the sublimation of the sulphur. After three or four hours, when the ore seems to be sufficiently de-sulphuretted, the heat is raised so as to melt the whole materials, and whenever they flux into a metallic glass, a few shovelfuls of bruised charcoal or cinders are thrown in, which soon thicken the liquid, and cause metallic lead to appear. By this means three-fourths of the lead contained in the ore are usually extracted; but at length the substance becoming less and less fluid, yields no more metal. Stamped and washed carbonate of iron (sparry iron ore) is now added, in the proportion of about 10 per cent. of the lead ore primarily introduced.

On stirring and working together this mixture, it assumes the consistence of a stiff paste, which is raked out of the furnace. When this has become cold, it is broken into pieces, and thereafter smelted in a slag-hearth, without the addition of flux. By this operation, almost the whole lead present is obtained. 100 quintals of schlich yield 45 of argentiferous lead; and in the production of 100 quintals (cwts.) of marketable lead, 140 cubic feet of beech-wood, and 357-1/2 quintals of charcoal are consumed.

This process is remarkable for the use of iron-ore in smelting galena.

10. Reduction in the reverberatory furnace, of the litharge obtained in the refining of lead.--The litharge of Alston Moor is seldom sold as such, but is usually converted into lead, in a reverberatory furnace.

In commencing this reduction, a bed of coal about 2 inches thick is first of all laid on the hearth; which is soon kindled by the flame of the fire-place, and in a little while is reduced to red hot cinders. Upon these a certain quantity of a mixture of litharge and small coal is uniformly spread; the heat of the fire-place being meanwhile so managed as to maintain in the furnace a suitable temperature for enabling the combustible to deprive the litharge of its oxygen, and to convert it into lead. The metal is run out by the tap-hole into an iron pot; and being cast into pigs of half a hundred weight, is sold under the name of refined lead at a superior price.

The quantity of small coal mixed with the litharge, should be somewhat less than what may be necessary to effect the reduction, because if in the course of the process, a deficiency of it is perceived in any part of the furnace, more can always be added; whereas a redundancy of coal necessarily increases the quantity of slag, which, at the end of the shift, must be removed from the furnace before a new operation is begun, whereby lead is lost. In the reverberatory furnace, six fodders of lead may be revived in nine or ten hours; during the first six of which the mixture of litharge and coal is added at short intervals. A fodder is from 21 to 24 cwts.

It deserves to be remarked that the work does not go on so well nor so quick when the coal and litharge are in a pulverulent form; because the reduction in this case takes place only at the surface, the air not being able to penetrate into the body, and to keep up its combustion, and the mutual action of the litharge and carbon in the interior. But on the other hand, when the litharge is in porous pieces as large as a hen’s egg, the action pervades the whole body, and the sooty fumes of the coal effect the reduction even in the centre of the fragments of the litharge, penetrating into every fissure and carrying off the oxygen. The heat ought never to be urged so far as to melt the litharge.

The grounds of the cupel, and the slag of the reduction furnace, being a mixture of small coke, coal ash, and oxide of iron, more or less impregnated with lead, are smelted upon the slag hearth, along with coke, and by way of flux, with a certain quantity of the black scoriæ obtained from the same furnace, prepared for this purpose, by running it out in thin plates, and breaking it into small pieces. The lead thus obtained is usually very white, very hard, and not susceptible of refinement.

MM. Dufrénoy and Beaumont consider the smelting of lead ore by the reverberatory furnace as practised in Derbyshire, as probably preferable to that with the slag hearth as carried on in Brittany; a process which seldom gives uniform products, while it occasions a more considerable waste of lead, and consumption of fuel.

The mixed process employed in Cumberland of roasting the ore, and afterwards smelting it in a small furnace resembling that called the Scotch, apparently yields a little less lead than if both operations were executed in the reverberatory furnace; but according to Mr. Forster, (see his Treatise on a Section of the Strata from Newcastle upon Tyne, &c.) this slight loss is more than compensated by the smaller consumption of fuel, the increased rapidity of the operation, and especially by the much greater purity of the lead obtained from the Scotch furnace. When it comes to be refined, the loss is only about one-twelfth or one-thirteenth, whereas the lead revived in the reverberatory furnace, loses frequently a ninth. Moreover, the lead furnished by the first method admits of being refined with profit, when it yields only 5 ounces of silver per fodder of 20 quintals, poids de marc, while that produced by the reverberatory furnace cannot be cupelled unless it gives 10 ounces per fodder; and as in the English cupellation, lead is constantly added anew without skimming, the litharge obtained in the second case can never be brought into the market, whereas the litharge of the leads from the Scotch furnace is of good quality. See the new method of enriching lead for cupellation, under SILVER.

As the smelting of galena, the principal ore of lead, is not a little complex, the following tabular view of the different processes may prove acceptable to the metallurgist:--

Treatment of Process of

{1. Pure ores } Pesey, Spain, { } &c. { {2. Ores mixed } England, in { with saline} general. { gangues. } { {3. Ores mixed { Viconago in { with earthy{ Italy, and { A { gangues. { Redruth in { De-sulphura- { { Cornwall. { tion by { { roasting. {4. Ores mixed } { { with sever-} Combined with { { al sul- } the above. { { phurets. } I. Class. { { Treated in { {5. Ores with } reverberatory { { earthy sa- } furnaces. { { line, and } { { sulphurous } { { gangues. } { { {6. Ores with } { B { mattes, as } Vienne, Poul- { De-sulphura- { at Vienne, } laouen, and { tion by iron. { in Dauphi- } Tarnowitz. { ny. }

{7. Ores pro- { Mattes, with }Many { ducing { raw lead. }places. { slags of } Workable lead,{ { A { various } without {Villefort. { Founding after{ silicates. } mattes. { { roasting in a { { heap, or in a {8. Ores pro- { Mattes and }Several II. Class. { reverberatory.{ ducing com-{ workable lead.}places. Treated in { { pound sili-{ Workable {Pont Gibaud the mill-slag-{ { cate slags.{ lead. {and Scotch hearth, the { { { {furnace. fourneau à { manche, or { B }9. Ores pro- { Mattes and }Baad-Ems, Scotch fur- { Founding with } ducing { workable }Hartz, nace. { direct de- } slags com- { lead. }Tarnowitz. { sulphuration } posed of } Poor mattes { { by metallic } silicates } and workable {Tarnowitz. { iron. } and sub- } lead. { { } silicates. } {

The annual production of lead in Europe may be estimated at about 80,000 tons; of which four-sevenths are produced in England, two-sevenths in Spain, the remainder in Germany and Russia. France does not produce more than one five-hundredth part of the whole; and only one-fiftieth of its consumption.

See LITHARGE, MINIUM, or Red Lead, SOLDER, SUGAR or Acetate of LEAD, TYPE METAL, and WHITE LEAD.

LEAD-SHOT; (Plomb de chasse, Fr.; Schrot, Flintenschrot, Germ.) The origin of most of the imperfections in the manufacture of lead-shot is the too rapid cooling of the spherules by their being dropped too hot into the water, whereby their surfaces form a solid crust, while their interior remains fluid, and in its subsequent concretion, shrinks, so as to produce the irregularities of the shot.

The patent shot towers originally constructed in England obviate this evil by exposing the fused spherules after they pass through the cullender, to a large body of air during their descent into the water tub placed on the ground. The greatest erection of this kind is probably at Villach in Carinthia, being 240 Vienna, or 249 English feet high.

The quantity of arsenic added to the mass of melted lead, varies according to the quality of this metal; the harder and less ductile the lead is, the more arsenic must be added. About 3 pounds of either white arsenic or orpiment is enough for one thousand parts of soft lead, and about 8 for the coarser kinds. The latter are employed preferably for shot, as they are cheaper and answer sufficiently well. The arsenical alloy is made either by introducing some of this substance at each melting; or by making a quantity of the compound considerably stronger at once, and adding a certain portion of this to each charge of lead. If the particles of the shot appear lens-shaped, it is a proof that the proportion of arsenic has been too great; but if they are flattened upon one side, if they are hollowed in their middle, called cupping by the workman, or drag with a tail behind them, the proportion of arsenic is too small.

The following is the process prescribed by the patentees, Ackerman and Martin. Melt a ton of soft lead, and sprinkle round its sides in the iron pot, about two shovelfuls of wood ashes, taking care to leave the centre clear; then put into the middle about 40 pounds of arsenic to form a rich alloy with the lead. Cover the pot with an iron lid, and lute the joints quickly with loam or mortar to confine the arsenical vapours, keeping up a moderate fire to maintain the mixture fluid for three or four hours; after which skim carefully, and run the alloy into moulds to form ingots or pigs. The composition thus made is to be put in the proportion of one pig or ingot into 1000 pounds of melted ordinary lead. When the whole is well combined, take a perforated skimmer and let a few drops of it fall from some height into a tub of water. If they do not appear globular, some more arsenical alloy must be added.

Lead which contains a good deal of pewter or tin must be rejected, because it tends to produce elongated drops or tails.

From two to three tons are usually melted at once in the large establishments. The surface of the lead gets covered with a crust of oxide of a white spongy nature, sometimes called cream by the workmen, which is of use to coat over the bottom of the cullender, because without such a bed the heavy melted lead would run too rapidly through the holes for the granulating process, and would form oblong spheroids. The mounting of this filter, or lining of the cullender, is reckoned to be a nice operation by the workmen, and is regarded usually as a valuable secret.

The cullenders are hollow hemispheres of sheet iron about 10 inches in diameter, perforated with holes, which should be perfectly round and free from burs. These must be of an uniform size in each cullender; but of course a series of different cullenders with sorted holes for every different size of lead shot, must be prepared. The holes have nearly the following diameters for the annexed numbers of shot.

No. 0. 1/50 of an inch. 1. 1/58 -- 2. 1/66 -- 3. 1/72 -- 4. 1/80 --

From No. 5. to No. 9. the diameter decreases by regular gradations, the latter being only 1/360 of an inch.

The operation is always carried on with three cullenders at a time; which are supported upon projecting grates of a kind of chafing dish made of sheet iron somewhat like a triangle. This chafing dish should be placed immediately above the fall; while at its bottom there must be a tub half filled with water for receiving the granulated lead. The cullenders are not in contact, but must be parted by burning charcoal in order to keep the lead constantly at the proper temperature, and to prevent its solidifying in the filter. The temperature of the lead bath should vary with the size of the shot; for the largest, it should be such that a bit of straw plunged into it will be scarcely browned, but for all it should be nicely regulated. The height from which the particles should be let fall varies likewise with the size of the shot; as the congelation is the more rapid, the smaller they are. With a fall of 33 yards or 100 feet, from No. 4. to No. 9. may be made; but for larger sizes, 150 feet of height will be required.

Every thing being arranged as above described, the workman puts the filter-stuff into the cullender, pressing it well against the sides. He next pours lead into it with an iron ladle, but not in too great quantity at a time, lest it should run through too fast. The shot thereby formed and found in the tub are not all equal.

The centre of the cullender being less hot affords larger shot than the sides, which are constantly surrounded with burning charcoal. Occasionally, also, the three cullenders employed together may have holes of different sizes, in which case the tub may contain shot of very various magnitudes. These are separated from each other by square sieves of different fineness, 10 inches broad and 16 inches long, their bottoms being of sheet iron pierced with holes of the same diameters as those of the cullenders. These sieves are suspended by means of two bands above boxes for receiving the shot; one sieve being usually set above another in consecutive numbers, for instance 1 and 2. The shot being put into the upper sieve, No. O. will remain in it, No. 1. will remain in the lower sieve, and No. 2. will, with all the others, pass through it into the chest below. It is obvious that by substituting sieves of successive fineness, shot of any dimension may be sorted.

In the preceding process the shot has been sorted to size; it must next be sorted to form, so as to separate all the spheroids which are not truly round, or are defective in any respect. For this purpose a board is made use of about 27 inches long and 16 broad, furnished partially with upright ledges; upon this tray a handful or two of the shot to be sorted being laid, it is inclined very slightly, and gently shaken in the horizontal direction, when the globular particles run down by one edge, into a chest set to receive them, while those of irregular forms remain on the sides of the tray, and are reserved to be re-melted.

After being sorted in this way, the shot requires still to be smoothed and polished bright. This object is effected by putting it into a small octagonal cask, through a door in its side, turning upon a horizontal iron axis, which rests in plummer boxes at its ends, and is made to revolve by any mechanical power. A certain quantity of plumbago or black lead is put in along with the shot.

LAZULITE (Eng. and Fr.; Lazulith, Germ.); is a blue vitreous mineral, crystallizing in rhomboidal dodecahedrons; spec. grav. 2·76 to 2·94; scratches glass; affords a little water by calcination; fusible into a white glass; dissolves in acids with loss of colour; solution leaves an alkaline residuum, after being treated with carbonate of ammonia, filtered, evaporated, and calcined. It consists of silica, 35·8; alumina, 34·8; soda, 23·2; sulphur, 3·1; carbonate of lime, 3·1. This beautiful stone affords the native ultramarine pigment, which was very costly till a mode of making it artificially was lately discovered. See ULTRAMARINE.

LEATHER, (Cuir, Fr.; Germ., Leder); is the skin of animals, so modified by chemical means as to have become unalterable by the external agents which tend to decompose it in its natural state. The preparation in a rude manner of this valuable substance, has been known from the most antient times, but it was not till the end of the last, and the beginning of the present century, that it began to be manufactured upon right principles, in consequence of the researches of Macbride, Deyeux, Seguin, and Davy. There are several varieties of leather; such as sole leather, boot or upper leather, shamoy leather, kid or glove leather, &c. Skins may be converted into leather either with or without their hairy coat.

We shall treat first of sole and upper leathers, being the most important, and most costly and difficult to prepare in a proper manner. These kinds consist of organized fibrous gelatine or skin, combined with the proximate vegetable principle, tannin, and probably also some vegetable extractive. Under the articles GALLS and TANNIN, will be found an account of the properties of this substance, and the means of obtaining it in a state of purity. Calf leather quickly tanned by an infusion of galls, consists of 61 parts of skin, and 39 of vegetable matter in 100 by weight; by solution of catechu, it consists of 80 of skin, and 20 of vegetable matter; by infusion of Leicester willow, of 74·5 skin, and 25·5 vegetable matter; and by infusion of oak bark, of 73·2 skin, and 26·8 vegetable matter. By the slow process of tanning, continued for three months, the increase of weight upon the skin in its conversion into leather, is greatly less; the vegetable constituents being from Leicester willow only 13 per cent. of the leather, and from oak bark 15 per cent. Sole leather, however, generally contains no less than 40 per cent. of vegetable matter. In every astringent bark, the inner white part next to the alburnum, contains the largest quantity of tannin, and the middle coloured part contains most extractive matter. The outer surface or epidermis seldom furnishes either tannin or extractive matter. Young trees abound most in the white cortical layers, and are hence more productive of tannin under equal weights, than the barks of old trees. In no case is there any reason to believe that the gallic acid of astringent vegetables is absorbed in the process of making leather; hence Seguin’s theory of the agency of that substance in disoxygenating skin, falls to the ground. The different qualities of leather made with the same kind of skin, seem to depend very much upon the different quantities of extractive matter it may have absorbed. The leather made with infusion of galls, is generally harder and more liable to crack than the leather obtained from infusions of barks; and it always contains a much larger proportion of tannin, and a smaller proportion of extractive matter.

When calf skin is slowly tanned in weak solutions of the bark, or of catechu, it combines with a good deal of extractive matter, and though the increase of the weight of the skin be comparatively small, yet it has become perfectly insoluble in water, forming a soft, but at the same time a strong leather. The saturated infusions of astringent barks contain much less extractive matter in proportion to their tannin, than the weak infusions; and when skin is quickly tanned in the former, it produces a worse and less durable leather than when slowly tanned in the latter. In quick tanning, a considerable quantity of vegetable extractive matter is thus lost to the manufacturer, which might have been made to enter as a useful constituent into the leather. These observations show that there is sufficient foundation for the opinion of the common workmen, concerning what is technically called feeding of leather, in the slow method of tanning; and though the processes of this art have been unnecessarily protracted by defective methods of steeping, and want of progressive infiltration of the astringent liquor through the skins, yet in general they appear to have arrived, in consequence of old experience, at a degree of perfection in the quality of the leather, which cannot be far exceeded by means of any theoretical suggestions which have been advanced.

On the first view it may appear surprising, that in those cases of quick tanning, where extractive matter forms a certain portion of the leather, the increase of weight is less than when the skin is combined with the pure tannin; but the fact is easily accounted for, when we consider that the attraction of skin for tannin must be probably weakened by its union with extractive matter; and whether we suppose that the tannin and extractive matter enter together into combination with the matter of skin, or unite with separate portions of it, still, in either case, the primary attraction of skin for tan must be to a certain extent diminished.

In examining astringent vegetables in relation to their power of making leather, it is necessary to take into account not only the quantity they may contain of the substance precipitable by gelatine, but likewise the quantity and the nature of the extractive matter; and in cases of comparison, it is essential to employ infusions of the same degree of concentration.

Of all astringent substances hitherto examined, catechu is that which contains the largest proportion of tannin; and in supposing, according to the usual estimation, that from four to five pounds of common oak bark are required to produce one pound of leather, it appears, from the various synthetical experiments, that about half a pound of catechu would answer the same purpose. Mr. Purkis found, by the results of different accurate experiments, that 1 pound of catechu was equivalent to 7 or 8 of oak bark. For the common purposes of the tanner, 1 pound of it would be equivalent also to 2-1/4 pounds of galls, to 7-1/2 of the Leicester willow, to 11 of the bark of the Spanish chesnut, to 18 of the bark of the common elm, to 21 of the bark of the common willow, and to 3 pounds of sumach.

Various menstrua have been proposed for the purpose of expediting and improving the process of tanning, among others, lime water, and solution of pearl-ash; but as these two substances form compounds with tannin which are not decomposable by gelatine, it follows that their effects must be prejudicial. There is very little reason to suppose that any bodies will be found which, at the same time that they increase the solubility of tannin in water, will not likewise diminish its attraction for skin.

In this country all tanned leather is distinguished into two kinds, called hides and skins; the former term being appropriated to that made from the larger animals, as bulls, buffaloes, oxen, and cows, into thick strong sole leather; and the latter to that made from calves, seals, &c., into thinner and more flexible upper leather. Sometimes the hides are brought into the market merely dried, as from Buenos-Ayres; or dried and salted, as from Bahia and Pernambuco; but the greater part are fresh from recently slaughtered animals. The heaviest ox hides are preferred for forming butts or backs, which are manufactured as follows:--

The washing process must be more or less elaborate, according to the state of the skins. Those that are salted and dry require to be steeped, beaten, and rubbed several times alternately, to bring them to the fresh condition.

After removing the horns, the softened or recent hides are laid in a heap for two or three days, after which they are suspended on poles in a close room called a smoke-house, heated somewhat above the common temperature by a smouldering fire. In these circumstances, a slight putrefaction supervenes, which loosens the epidermis, and renders the hair easily detachable by the fleshing knife; a large two-handled implement, with a blunt edge, and bent to suit the curvature of the rounded beam of the wooden horse upon which the hide is scraped. See CURRYING.

The next step is immersion in a pit containing water impregnated with about a 1000th part of sulphuric acid. This process is called raising, because it distends the pores, and makes the fibres swell, so as to render the skins more susceptible of the action of the tanning infusions. Forty-eight hours in general suffice for this operation, but more time may be safely taken.

When the hides are found to be sufficiently raised, they are transferred to a pit, in which they are stratified with oak bark, ground by a proper mill into a coarse powder. The pit is then filled up with an infusion of oak bark called ooze, and the hides are allowed to remain in it for about a month or six weeks. By this time the tannin and extractive matter of the bark having combined intimately with the animal fibre, the pit is exhausted of its virtue, and must be renewed, by taking out the spent bark, and subjecting the skins to a fresh dose of oak bark and ooze. The hides which were placed near the top of the first pit, must be placed near the bottom of the next. In this mixture they remain, upon the old practice, about three months. The last process being repeated twice or thrice, perfectly tanned leather is the result. The hides are now removed from the pit, and hung up in a shed. In the progress of drying, which should be slow, they are compressed with a steel tool, and beaten smooth, to render them more firm and dense.

Some manufacturers place on the bottom of the pit 5 or 6 inches of spent bark, over it 2 inches of fresh bark, then a skin; and so, alternately, a layer of new bark and a skin, till the pit is nearly full, reserving a small space at top for a thicker layer of bark, over which weighted boards are laid, to condense the whole down into the tanning infusion.

The operation of tanning sole leather in the above way, lasts a year or a year and a half, according to the quality wanted, and the nature of the hides.

A perfect leather is recognized by its section, which should have a glistening marbled appearance, without any white streaks in the middle.

Crop hides are manufactured by immersion, during three or four days, in pits containing milk of lime; in which they are occasionally moved up and down in order to expose them equally to the action of this menstruum. They are then removed, and cleared from hair and impurities, by using the fleshing knife upon the horse; after which they must be completely freed from the lime by a thorough washing. They are next plunged in pits containing a weak ooze or infusion of oak bark, from which they are successively transferred into other pits with stronger ooze; all the while being daily handled, that is, moved up and down in the infusion. This practice is continued for about a month or six weeks. They are now ready to be subjected to a mixture of ground oak bark and stronger ooze in other pits, to a series of which they are progressively subjected during two or three months.

The hides are next put into large vats, called layers, in which they are smoothly stratified with more oak bark, and a stronger infusion of it. After six weeks they are taken out of these vats, and subjected to a new charge of the same materials for two months. This simple process is repeated twice or thrice, at the option of the manufacturer, till the hides are thoroughly tanned. They are then slowly dried, and condensed in the manner above described. These crop hides form the principal part of the sole leather used for home consumption in England.

The process of tanning skins (as of calves, seals, &c.) is in some respects peculiar. They are left in the lime pits for about twelve days, when they are stripped of their hair, washed in water, then immersed in a lixivium of pigeons’ dung, called a grainer, of an alkaline nature. Here they remain from eight to ten days, according to the state of the atmosphere, during which time they are frequently handled, and scraped on both sides upon a convex wooden beam. This scraping or working, as it is termed, joined to the action of the grainer, serves to separate the lime, oil, and glutinous matter, and to render the skin pliant, soft, and ready to imbibe the tanning principle. They are with this view transferred into pits containing a weak solution of bark, in which they undergo nearly the same treatment as described above for crop hides; but they are not commonly stratified in the layers. The time occupied in tanning them is usually limited to three months. They are then dried, and disposed of to the currier, who dresses and blackens them for the upper leathers of boots and shoes, for harness, and other purposes. The light and thin sorts of cow and horse hides are often treated like calf skins.

In all the above processes, as the animal fibres on the surface of the skin absorb most readily the tanning principles, and thereby obstruct, in a certain degree, their passage into the interior fibres, especially of thick hides, it becomes an object of importance to contrive some method of overcoming that obstacle, and promoting the penetration of the tan. The first manufacturer who appears to have employed efficacious mechanical means of favouring the chemical action was Francis G. Spilsbury, who in April, 1823, obtained a patent for the following operation:--After the hides are freed from the hairs, &c. in the usual way, they are minutely inspected as to their soundness, and if any holes be found, they are carefully sewed up, so as to be water tight. Three frames of wood are provided of equal dimensions, fitted to each other, with the edges of the frames held together by screw bolts. A skin about to be tanned is now laid upon the frame, and stretched over its edges, then the second frame is to be placed upon it, so that the edges of the two frames may pinch the skin all round and hold it securely; another such skin is then stretched over the upper surface of the second frame, in like manner, and a third frame being set upon this, confines the second skin. The three frames are then pinched tightly together by a series of screw bolts, passing through ears set round their outer edges, which fix the skin in a proper manner for being operated upon by the tanning liquor.

A space has been thus formed between the two skins, into which, when the frames are set upright, the infusion is introduced by means of a pipe from the cistern above, while the air is permitted to escape by a stopcock below. This cock must of course be shut whenever the bag is filled, but the one above is left open to maintain a communication with the liquor cistern, and to allow the hydrostatic pressure to force the liquor through the cutaneous pores by a slow infiltration, and thus to bring the tannin into contact with all the fibres indiscriminately. The action of this pressure is evinced by a constant perspiration on the outer surfaces of the skins.

When the tanning is completed, the upper stopcock is closed, and the under is opened to run off the liquor. The frames are now removed, the bolts are unscrewed, and the pinched edges of the skins pared off; after which they are to be dried and finished in the usual manner.

A modification of this ingenious and effectual process was made the subject of a patent, by William Drake, of Bedminster, tanner, in October, 1831. The hides, after the usual preparatory processes, are immersed in a weak tan liquor, and by frequent handling or turning over, receive an incipient tanning before being submitted to the infiltration plan. Two hides, as nearly of the same size and shape as possible, are placed grain to grain, when their corresponding edges are sewed firmly together all round by shoemaker’s waxed thread, so as to form a bag sufficiently tight to hold tan liquor. This bag must then be suspended by means of loops sewed to its shoulder end, upon pegs, in such a manner that it may hang within a wooden-barred rack, and be confined laterally into a book form. About an inch of the bag is left unsewed at the upper end, for the purpose of introducing a funnel through which the cold tan liquor is poured into the bag till it be full. After a certain interval which varies with the quality of the hides, the outer surface becomes moist, and drops begin to form at the bottom of the bag. These are received in a proper vessel, and when they accumulate sufficiently may be poured back into the funnel; the bag being thus, as well as by a fresh supply from above, kept constantly distended.

When the hides are observed to feel hard and firm, while every part of them feels equally damp, the air of the tanning apartment having been always well ventilated, is now to be heated by proper means to a temperature gradually increasing from 70° to 150° of Fahrenheit’s scale. This heat is to be maintained till the hides become firmer and harder in all parts. When they begin to assume a black appearance in some parts, and when the tan liquor undergoes little diminution, the hides may be considered to be tanned, and the bag may be emptied by cutting a few stitches at its bottom. The outer edges being pared off, the hides are to be finished in the usual way. During their suspension within the racks, the hides should be shifted a little sideways, to prevent the formation of furrows by the bars, and to facilitate the equable action of the liquor.

By this process the patentee says, that a hide may be tanned as completely in ten days as it could be in ten months by the usual method. I have seen a piece of sole leather thus rapidly tanned, and it seemed to be perfect. How it may wear, compared with that made in the old way, I cannot pretend to determine.

Messrs. Knowlys and Duesbury obtained a patent in August, 1826, for accelerating the impregnation of skins with tannin, by suspending them in a close vessel, from which the air is to be extracted by an air pump, and then the tanning infusion is to be admitted. In this way, it is supposed to penetrate the hide so effectually as to tan it uniformly in a short time.

About 32 years ago, a similar vacuum scheme was employed to impregnate with weaver’s paste or starch, the cops of cotton weft, for the dandy looms of Messrs. Radcliff and Ross, of Stockport.

Danish leather is made by tanning lamb and kid skins with willow bark, whence it derives an agreeable smell. It is chiefly worked up into gloves.

Of the tawing or dressing of skins for gloves, and white sheep leather.

The operations of this art are: 1. washing the skins; 2. properly treating them with lime; 3. taking off the fleece; 4. treatment in the leather steep.

A shed erected upon the side of a stream, with a cistern of water for washing the skins; wooden horses for cleaning them with the back of the fleshing knife; pincers for removing the fibres of damaged wool; a plunger for depressing the skins in the pits; a lime pit; a pole with a bag tied to the end of it; a two-handed fleshing knife; a rolling pin, from 15 to 18 inches long, thickened in the middle; such are some of the utensils of a tawing establishment. There must be provided also a table for applying the oil to the skins; a fulling mill, worked by a water-wheel or other power; a dressing peg; a press for squeezing out the fatty filth; a stove; planks mounted upon legs, for stretching the skins, &c.

Fresh skins must be worked immediately after being washed, and then dried, otherwise they ferment, and contract either indelible spots, or get tender in certain points, so as to open up and tear under the tools. When received in the dry state they should be steeped in water for two days, and then treated as fresh skins. They are next strongly rubbed on the convex horse-beam with a round-edged knife, in order to make them pliant. The rough parts are removed by the fleshing knife. One workman can in this way prepare 200 skins in a day.

The flesh side of each being rubbed with a cold cream of lime, the skins are piled together with the woolly side of each pair outermost, and the flesh sides in contact. They are left in this state for a few days, till it is found that the wool may be easily removed by plucking.

They are next washed in running water, to separate the greater part of the lime, stripped of the wool by small spring tweezers, and then fleeced smooth by means of the rolling-pin, or sometimes by rubbing with a whetstone. Unless they be fleeced soon after the treatment with lime, they do not well admit of this operation subsequently, as they are apt to get hard.

They are now steeped in the milk of lime-pit, in order to swell, soften, and cleanse them; afterwards in a weak pit of old lime-water, from which they are taken out and drained. This steeping and draining upon inclined tables, are repeated frequently during the space of 3 weeks. Only the skins of young animals, or those of inferior value are tawed. Sometimes the wool is left on, as for housings, &c.

The skins, after having been well softened in the steeps, are rubbed on the outside with a whetstone set in a wooden case with two handles, in order to smooth them completely by removing any remaining filaments of wool. Lamb skins are rubbed with the pin in the direction of their breadth, to give them suppleness; but sheep skins are fulled with water alone. They are now ready for the branning, which is done by mixing 40 lbs. of bran with 20 gallons of water, and keeping them in this fermentable mixture for three weeks--with the addition, if possible, of some old bran water. Here they must be frequently turned over, and carefully watched, as it is a delicate operation. In the course of two days in summer, and eight in winter, the skins are said to be raised, when they sink in the water. On coming out of the bran, they are ready for the white stuff; which is a bath composed of alum and sea-salt. Twelve, fourteen, and sometimes eighteen pounds of alum for 100 skins, form the basis of the bath; to which two and a half pounds of salt are added in winter, and three in summer. These ingredients are introduced into a copper with twelve gallons of water. The salt aids in the whitening action. When the solution is about to boil, three gallons of it are passed through the cullender into a basin; in this 26 skins are worked one after another, and after draining, they are put together into the bath, and left in it for ten minutes to imbibe the salts. They are now ready to receive the paste. For 100 skins, from 13 to 15 pounds of wheat flour are used along with the yolks of 50 eggs. After having warmed the alum bath through which the skins have been passed, the flower is dusted into it, with careful stirring. The paste is well kneaded by the gradual addition of the solution, and passed through the cullender, whereby it becomes as clear as honey. To this the yolks being added, the whole is incorporated with much manual labour. The skins are worked one after another in this paste; and afterwards the whole together are left immersed in it for a day. They are now stretched and dried upon poles, in a proper apartment, during from 8 to 15 days, according to the season.

The effects of the paste are to whiten the skins, to soften them, and to protect them from the hardening influence of the atmosphere, which would naturally render them brittle. They would not bear working upon the softening iron, but for the emulsion which has been introduced into their substance. With this view they are dipped in a tub of clear water during five or six minutes, and then spread and worked upon the board. They are increased by this means in length, in the proportion of 5 to 3. No hard points must be left in them. The whiteness is also better brought out by this operation, which is performed upon the flesh side. The softening tool is an iron plate, about one foot broad, rounded over above, mounted upon an upright beam, 30 inches high, which is fixed to the end of a strong horizontal plank, 3-1/2 feet long, and 1 broad. This plank is heavily loaded, to make it immovable upon the floor. Sometimes the skins are next spread over an undressed clean skin upon the horse, and worked well with the two-handled knife, for the purpose of removing the first and second epidermis, called the fleur and arrière-fleur by the French megissiers. They are then dried while stretched by hooks and strings. When dry they are worked on the stretching iron, or they are occasionally polished with pumice stone. A delicate yellow tint is given by a composition made of two parts of whitening, and one of ochre, applied in a moistened state, and well worked in upon the grain side. After being polished with pumice, they are smoothed with a hot iron, as the laundresses do linen, whereby they acquire a degree of lustre, and are ready to be delivered to the glover.

For housings, the best sheepskins are selected, and such as are covered with the longest and most beautiful fleece. They are steeped in water, in order to be cleaned and softened; after which they are thinned inside by the fleshing knife. They are now steeped in an old bran pit for 3 or 4 days, when they are taken out and washed. They are next subjected to the white or alum bath, the wool being carefully folded within; about 18 pounds of alum being used for 100 skins. The paste is made as for the fleeced skins, but it is merely spread upon their flesh side, and left upon them for 18 hours, so as to stiffen. They are then hung up to dry. They are next moistened by sprinkling cold water upon them, folded up, piled in a heap, and covered with boards weighted with heavy stones; in which state they remain for two days. They are next opened with a round iron upon the horse, and subjected to the stretching iron, being worked broadwise. They are dried with the fleece outermost, in the sun if possible; and are finished upon the stretcher.

Calf and lamb skins with their hair and wool are worked nearly in the same manner; only the thicker the skin, the stronger the alum bath ought to be. One pound of alum and one of salt are required for a single calf skin. It is left four days in this bath, after which it is worked upon the stretcher, then fulled. When half dry the skins are opened upon the horse. In eight days of ordinary weather, they may be completely dressed. Lamb skins are sometimes steeped during eight days in a bath prepared with unbolted rye flour and cold water, in which they are daily moved about two or three times. They are then dried, stretched upon the iron, and switched upon the fleecy side.

Chamois or Shamoy leather.--The skins are first washed, limed, fleeced, and branned as above described. They are next efflowered, that is, deprived of their epidermis by a concave knife, blunt in its middle part, upon the convex horse-beam. The cutting part serves to remove all excrescences, and to equalize the thickness, while the blunt part softens and smooths. The skins of goats, does, and chamois are always treated in this way. They are next subjected to the fermenting bran steep for one or two days, in ordinary weather; but in hot weather for a much shorter time, sometimes only moving them in the sour bran liquor for a few minutes. They are lastly wrung at the peg, and subjected to the fulling mill.

When the skins have been sufficiently swelled and suppled by the branning, they may receive the first oil as follows: a dozen skins being stretched upon the table, the fingers are dipped in the oil, and shaken over the skins in different places, so as to impart enough of it to imbue the whole surface slightly, by friction with the palms of the hands. It is to the outside or grain that the oil is applied. The skins are folded four together, so as to form balls of the size of a hog’s bladder, and thrown into the trough of the fulling mill, to the number of twelve dozen at once. Here they remain exposed to the beater for two, three, or four hours, according to their nature and the state of the weather. They are taken out, aired, oiled, and again fulled. The airing and fulling are repeated several times, with more or less frequent oilings. Any cheap animal oil is employed.

After these operations, the skins require to be subjected to a fermenting process, to dilate their pores, and to facilitate their combination with the oil. This is performed in a chamber only 6 feet high, and 10 or 12 feet square. Poles are suspended horizontally a few inches from the ceiling, with hooks fixed in them to which the skins are attached. A somewhat elevated temperature is maintained, and by a stove if need be. This operation requires great skill and experience.

The remainder of the epidermis is next removed by a blunt concave knife and the horse; whereby the surface is not cut, but rather forcibly scraped.

The skins are now scoured to carry off the redundant oil; which is effected by a potash lye, at two degrees Baumé, heated no hotter than the hand can bear. In this they are stirred briskly, steeped for an hour, and lastly wrung at the peg. The soapy liquor thus expelled is used for inferior purposes. The clean skins after being dried, are finished first on the stretcher-iron, and then on the herse or stretching frame.

Leather of Hungary.--This is manufactured by impregnating strong hides with alum, common salt, and suet; by a rapid process which is usually completed in the space of two months. The workshop is divided into two parts; 1. a shed on the side of a stream, furnished with wooden horses, fleshing knives, and other small tools. In one corner is a furnace with a boiler for dissolving the alum, a vat for immersing the hides in the solution, and several subsidiary tubs. 2. A chamber, 6 feet high, by 15 feet square, capable of being made very tight, for preserving the heat. In one corner is a copper boiler, of sufficient size to contain 170 pounds of tallow. In the middle of the stove is a square stone slab, upon which an iron grate is placed about a yard square. This is covered with charcoal. At each side of the stove are large tables, which occupy its whole length, and on which the leather is spread to receive the grease. The upper part below the ceiling is filled with poles for hanging the leather upon to be heated. The door is made to shut perfectly close.

The first operations are analogous to those of tanning and tawing; the skins being washed, cut in halves, shaved, and steeped for 24 hours in the river. They are then cleaned with 5 or 6 pounds of alum, and 3-1/2 pounds of salt, for a piece of hide which weighs from 70 to 80 pounds. The common salt softens the effect of the alum, attracts the moisture of the air, and preserves the suppleness of the skin. When the alum and salt are dissolved, hot water is poured upon the hides placed in a vat, and they are tramped upon by a workman walking repeatedly from one end of the vat to the other. They are then transferred into a similar vat containing some hot water, and similarly tramped upon. They are next steeped for eight days in alum water. The same round of operations is repeated a second time.

The skins are now dried either in the air, or a stove room; but before being quite dry, they are doubled together, well stretched to take out the wrinkles, and piled up. When dry, they are again tramped to open the pores as well as to render the skin pliant, after which they are whitened by exposure to the sun.

Tallow of inferior quality is employed for greasing the leather. With this view the hides are hung upon the poles in the close stove room, then laid upon the table, and besmeared with the tallow melted till it begins to crackle. This piece is laid on another table, is there covered with a second, similarly greased, and so forth. Three pounds of fat are commonly employed for one piece of leather.

When the thirty strips, or fifteen hides passed through the grease in one operation are completed, two workmen take the first piece in their hands, and stretch it over the burning charcoal on the grate for a minute, with the flesh side to the fire. The rest are passed over the flame in like manner. After flaming, the pieces are successively laid on an inclined table exposed to the fire, where they are covered with a cloth. They are finally hung upon poles in the air to dry; and if the weather be warm, they are suspended only during the night, so as to favour the hardening of the grease. Instead of the alum bath, M. Curaudau has employed with advantage a steep of dilute sulphuric acid.

Morocco leather.--The true morocco leather is goat skin tanned and then dyed on the side of the grain. Sheep skins are treated in the same way. The skins are steeped first in a fermenting mixture of bran water for a few days, they are then worked upon the horse, steeped in fresh water for 12 hours, and rinsed in the same. They are next drained, steeped in weak lime pits for a proper time, till the hairs can be readily detached. They are now subjected to the action of a blunt knife upon the horse-beam, in order to strip off their hair, after which they are cleansed in running water. Any excrescences must be carefully removed with the fleshing knife, and their edges neatly pared. The next process is rubbing them strongly with a piece of hard schist, set in a wooden frame, in order to expel by the pressure any lime which may still adhere, and to soften the grain. They are now worked upon the horse-beam with the blunt knife, and subjected to a species of fulling, by being agitated by pegs in a revolving cask along with water. Many manufacturers prefer a weak alkaline lye, or putrified urine, to the lime bath.

The skins are immersed for a night and a day, in a bran bath, in a certain state of fermentation, then worked on the horse, and salted, to preserve them till they are to be dyed.

Preparatory to being dyed, each skin is sewed together edgewise, with the grain on the outside, and it is then mordanted either with a solution of tin, or with alum water. The colour is given by cochineal, of which from 10 to 12 ounces are required for a dozen of skins. The cochineal being boiled in water along with a little tartar or alum for a few minutes, forms a red liquor, which is filtered through a linen cloth, and put into a clean cask. The skins are immersed in this bath, and agitated in it for about half an hour; they are taken out and beaten, and then subjected to a second immersion in the cochineal bath. After being thus dyed, they are rinsed and tanned with Sicilian sumach, at the rate of two pounds for a skin of moderate size. This process is performed in a large tub made of white wood, in the liquor of which the skins are floated like so many bladders, and moved about by manual labour during four hours. They are then taken out, drained, and again subjected to the tanning liquor; the whole process requiring a space of twenty-four hours. The skins are now unstitched, rinsed, fulled with beetles, drained, rubbed hard with a copper blade, and lastly hung up to dry.

Some manufacturers brighten the colour by applying to the surface of the skins, in a damp state, a solution of carmine in ammonia with a sponge; others apply a decoction of saffron to enliven the scarlet tint. At Paris the morocco leather is tanned by agitation with a decoction of sumach in large casks made to revolve upon a horizontal axis, like a barrel churn. White galls are sometimes substituted for sumach; a pound being used for a skin. The skins must be finally cleaned with the utmost care.

The black dye is given by applying with the brush a solution of red acetate of iron to the grain side. Blue is communicated by the common cold indigo vat; violets, with a light blue followed by cochineal red; green, by Saxon blue followed by a yellow dye, usually made with the chopped roots of the barberry. This plant serves also for yellows. To dye olive, the skins are first passed through a weak solution of green vitriol, and then through the decoction of barberry root, containing a little Saxon blue. Puce colour is communicated by logwood with a little alum; which may be modified by the addition of a little Brazil wood. In all these cases, whenever the skins are dyed, they should be rinsed, wrung or rather drained, stretched upon a table, then besmeared on the grain side with a film of linseed oil applied by means of a sponge, in order to promote their glossiness when curried, and to prevent them becoming horny by too rapid drying.

The last process in preparing morocco leather is the currying, which brings out the lustre, and restores the original suppleness. This operation is practised in different manners, according to the purpose the skins are to serve. For pocket-books, portfolios, and case-making in general, they must be thinned as much as possible upon the flesh side, moistened slightly, then stretched upon the table, to smooth them; dried again, moistened, and lastly passed two or three times through the cylinder press in different directions, to produce the crossing of the grain. The skins intended for the shoemaker, the saddler, the bookbinder, &c., require more pliancy, and must be differently curried. After being thinned, they are glazed with a polisher while still moist, and a grain is formed upon the flesh side with the roughened lead plate or grainer of the curriers, called in French pommelle; they are glazed anew to remove the roughness produced by the pommel, and finally grained on the flesh side with a surface of cork applied under a pommel of white wood.

Russia leather.--The Russians have long been possessed of a method of making a peculiar leather, called by them jucten, dyed red with the aromatic saunders wood. This article has been much sought after, on account of not being subject to mould in damp situations, being proof against insects, and even repelling them from the vicinity of its odour. The skins are freed from the hair or fleece, by steeping in an ash-lye too weak to act upon the animal fibres. They are then rinsed, fulled for a longer or shorter time according to their nature, and fermented in a proper steep, after having been washed in hot water. They are taken out at the end of a week, but they may be steeped a second time if deemed necessary, to open their pores. They are now cleaned by working them at the horse on both the flesh and grain sides.

A paste is next composed, for 200 skins, of 38 pounds of rye flour, which is set to ferment with leaven. This dough is worked up with a sufficient quantity of water to form a bath for the skins, in which they are soaked for 48 hours; they are then transferred into small tubs, where they remain during fifteen days, after which they are washed at the river. These operations serve to prepare the skins for absorbing the astringent juices with uniformity. A decoction of willow bark (salix cinerea, and salix caprea) being made, the skins are immersed in the boiler whenever the temperature of the liquor is sufficiently lowered not to injure the animal fibres, and handled and pressed for half an hour. This manipulation is repeated twice daily during the period of a week. The tanning infusion is then renewed, and applied to the same skins for another week; after which being exposed to the air to dry, they are ready for being dyed, and then curried with the empyreumatic oil of the bark of the birch tree. To this substance the Russia leather owes its peculiarities. Many modes have been prescribed for preparing it; but the following is the one practised in Russia.

The whitish membranous epidermis of the birch, stripped of all woody parts, is introduced into an iron boiler, which, when stuffed full, is covered tight with a vaulted iron lid, having a pipe rising from its centre. A second boiler into which this pipe passes without reaching its bottom, is set over the first, and is luted to it at the edges, after the two are bolted together. They are then inverted, so that the upper one contains the birch bark. The under half of this apparatus is sunk in the earth, the surface of the upper boiler is coated over with a clay lute, then surrounded with a fire of wood, and exposed to a red heat, till the distillation be completed. This operation, though rude in appearance, and wasteful of wood, answers its purpose perfectly well. The iron cylinder apparatus used in Britain for distilling wood vinegar, would, however, be much more convenient and productive. When the above boilers are unluted, there is found in the upper one a very light powder of charcoal, and in the under one which served as a receiver, there is an oily, brown, empyreumatic fluid, of a very strong smell, which is mixed with the tar, and which floats over a small quantity of crude vinegar. The former matter is the oil employed to impregnate the skins, by working it into the flesh side with the curriers’ tools. It is difficult to make this oil penetrate with uniformity; and the Russians do not always succeed in this process, for they turn out many skins in a spotted state. This oil is at present obtained in France by distilling the birch bark in copper stills, and condensing the products by means of a pipe plunged in cold water. About 60 per cent. of the weight of the bark is extracted.

The skins imbibe this oil most equally before they are fully dry. Care must be taken not to apply too much of it, for fear of its passing through and staining the grain-side of the leather. Chevreul has investigated the chemical nature of this odoriferous substance, and finding it to be a peculiar compound, has called it betuline.

LEDUM PALUSTRE. This plant is employed in Russia to tan the skins of goats, calves, and sheep, into a reddish leather of an agreeable smell; as also in the preparation of the oil of birch, for making what is commonly called Russia leather.

LEGUMINE, is the name of a vegeto-alkali supposed to exist in leguminous plants.

LEMONS. See CITRIC ACID, and OILS, ESSENTIAL.

LEVIGATION, is the mechanical process whereby hard substances are reduced to a very fine powder.

LEUCITE, is a hard Vesuvian mineral, consisting of silica, 54; alumina, 23; potash, 23.

LEUCINE, is a white crystalline substance produced by acting upon flesh with sulphuric acid.

LEWIS, is the name of one kind of shears used in cropping woollen cloth.

LIAS, is a fine-grained argillaceous limestone, whose geological position is under the oolite; it is the proper lithographic stone.

LIBAVIUS, LIQUOR OF, is the bichloride of tin, prepared by dissolving that metal with the aid of heat, in aqua regia, or by passing chlorine gas through a solution of muriate of tin till no more gas be absorbed, evaporating the solution, and setting it aside to crystallize. The anhydrous bichloride is best prepared by mixing four parts of corrosive sublimate with one part of tin, previously amalgamated with just so much mercury as to render it pulverizable; and by distilling this mixture with a gentle heat. A colourless fluid, the dry bichloride of tin, or the proper fuming liquor of Libavius, comes over. When it is mixed with one-third of its weight of water it becomes solid. The first bichloride of tin is used in calico-printing.

LICHEN. See ARCHIL.

LIGNEOUS MATTER, is vegetable fibre. See FIBROUS MATTER.

LIGNITE, is one of the most recent geological formations, being the carbonaceous remains of forest trees. From this substance, as found in the neighbourhood of Cologne, the brown colours, called umber and earth of Cologne, are prepared.

LILAC DYE. See CALICO-PRINTING AND DYEING.

LIMESTONE (Calcaire, Fr.; Kalkstein, Germ.); may be classed under the following heads:--

1. Calcareous spar occurs in colourless crystals or crystalline masses; dissolves with effervescence in muriatic acid; is scratched by soft iron, but not by the nail; specific gravity 2·7; loses 46 per cent. by the expulsion of carbonic acid, and calcines into quicklime.

2. Calcsinter, or stalactitic carbonate of lime, called also concretionary limestone, because formed of zones more or less undulated, and nearly parallel. These zones have a fibrous structure, arising from the successive deposits of the crystalline limestone from its solvent water. The long conical pieces called stalactites, show fibres converging to the axis. The tubercular consists of irregular lumps often sprinkled over with small crystals, and associated so as to exhibit the appearance of cauliflower. The stratiform, commonly called stalagmite, or alabaster limestone, represents zones not concentric, but spread out, waving, and parallel; its texture is sometimes lamellar, and sometimes fibrous. These waving strata are distinguishable from one another by their different densities, and by their degrees of translucency. This stalagmitic mass bears the name of oriental alabaster, when it is reddish-yellow with distinct zones, and is susceptible of a fine polish. Stalactites are formed in the large excavations of calcareous rocks. The water percolating down through them, and dropping from the roofs of the caverns, is usually charged with carbonate of lime held in suspension by an excess of carbonic acid. The exposure to air, the motion, and the consequent diminution of pressure, cause the precipitation of the carbonate of lime in the solid state. Each drop of water, on falling through the vault, abandons a small film of limestone, which enlarges by degrees, and forms either a cylinder or solid mass. This alabaster differs from marble in its parallel and waving layers, and its faint degree of transparency.

This alabaster serves for the decoration of public buildings, and is occasionally introduced into certain pieces of furniture. The fine Egyptian alabaster was anciently brought from the mountains of the Thebaid, between the Nile and the Red Sea, near a town called Alabastron, whence probably the name. Very fine red alabaster, of great hardness, was found at one time in the quarries of Montmartre, but the stock was soon exhausted.

The incrusting concretionary limestone differs little from the preceding except in the rapidity of its formation, and in being moulded upon some body whose shape it assumes. These deposits from calcareous springs, form equally on vegetable bodies, on stones, metals, within pipes of cast iron, wood, or lead. The incrustations on vegetable and animal substances are vulgarly called petrifactions, as the organic fibres are replaced by stone. One of the most curious springs of this nature is at the baths of Saint Philip, in Tuscany, where the water flows in almost a boiling state, over an enormous mass of alabaster which it has produced. The carbonate of lime seems to be held in solution here by sulphuretted hydrogen, which flies off when the water issues to the day. Dr. Vegny has taken advantage of this property of the spring, to obtain basso-relievo figures of great whiteness and solidity. He makes use of sulphur moulds.

Calcareous tuf consists of similar incrustations made by petrifying rivulets running over mud, sand, vegetable remains, &c. It is porous, even cellular, somewhat soft, impure, and of a dirty gray colour. Its surface is wavy, rough, and irregular. These incrustations or deposits are, however, sometimes so abundant, and the resulting stony matters so hard that buildings may be constructed with them. The stone with which the town of Pasti, in Italy, is built has been called pipe-stone by the Italians; and it has apparently derived its origin from incrustations upon large reeds.

The travertino, which served to construct all the monuments of Rome, appears to have been formed by the deposits of the Anio and the solfatara of Tivoli. The temples of Pæstum, which are of extreme antiquity, have been built with a travertino formed by the sediment of the waters which still flow in this territory. All these stones acquire great hardness in the air, and M. de Breislak thinks that it is to the happy union of travertino and pouzzolana in the same spot, that the monuments of Rome owe their great solidity.

Spongy limestone, usually called Agaric mineral, stone marrow, &c., belongs to this kind of formation. It has a very white colour, a very fine grain, is soft to the touch, very tender, and light enough to float for an instant on water. It occurs in rather thin layers, in the crevices of calcareous rocks, and is so common in Switzerland as to be employed for whitening houses.

3. Compact limestone, is of a grain more or less fine, does not polish, nor afford large blocks free from fissures, has a conchoidal, or uneven scaly fracture. Colours very various. Its varieties are; a, The sub-lamellar, compact, with some appearance of a foliated texture. b, Compact fine-grained limestone, the zechstein of the Germans, to which M. Brongniart refers the lithographic stone in his classification of rocks (Dictionnaire des Sciences Naturelles,) but the English geologists place the locality of the famous lithographic quarry of Solenhofen much higher in the plane of secondary superposition. Its fracture is conchoidal; colour from gray to whitish; c, Compact common limestone. Grain of middle size; earthy aspect; uneven fracture; perfectly opaque; colour, whitish to pale gray, yellow, or reddish. The limestones of the Jura formation are referred to this head, as well as most of those interspersed among the coal strata. d, The coarse compact, or Cornbrash; texture somewhat open, earthy aspect, rough to the touch, ragged fracture, colour yellow, gray, or dirty red. e, Compact cellular, the Rauchekalk and Holekalk of the Germans, on account of the numerous holes or caverns distributed through it.

4. Oolite or roe-stone.--It consists of spherical grains of various size, from a millet seed, to a pea, or even an egg; texture compact; fracture even; colours, whitish, yellow, gray, reddish, brownish. The larger balls have almost always a foreign body for their centre or nucleus.

5. Chalk; texture earthy; grains fine, tender, friable; colours white, grayish, or pale yellowish.

6. Coarse-grained limestone; an earthy texture, in large particles, often loose; fracture foliated, uneven; colour pale and dirty yellow. Coarse lias has has been referred to this head.

7. Marly limestone; lake and fresh-water limestone formation; texture fine-grained, more or less dense; apt to crumble down in the air; colour white or pale yellow; fracture rough-grained, sometimes conchoidal; somewhat tenacious. Texture occasionally cavernous; with cylindrical winding cavities. This true limestone must not be confounded with the lime-marl, composed of calcareous matter and clay.

8. Siliceous limestone; of a compact texture; scratching steel, and scratched by it; leaves a siliceous residuum after the action of muriatic acid.

9. Calp; texture compact; fine-grained; schistose structure; hard, as the preceding; not burning into quicklime, affording to dilute muriatic acid a copious residuum of clay and silica; colour blackish; found in beds in the transition district near Dublin.

10. Lucullite or stinkstone; texture compact or sub-lamellar, colour grayish; emits the smell of sulphuretted hydrogen by friction or a blow. It occurs at Assynt, in Sutherlandshire; in Derbyshire; counties of Kilkenny, Cork, and Galway.

11. Bituminous limestone; black or blackish colour; diffusing by the action of fire a bituminous odour, and becoming white.

Of all common limestones the purity may most readily be determined by the quantity of carbonic acid which is evolved during their solution in dilute nitric or muriatic acid. Perfect carbonate of lime loses in this way 46 per cent.; and if any particular limestone loses only 23 per cent., we may infer that it contains only one half its weight of calcareous carbonate. This method is equally applicable to marls, which are mixtures in various proportions of carbonate of lime, clay, and sand, and may all be recognized by their effervescing with acids.

The chief use of calcareous stones is for procuring quicklime by calcination in proper furnaces; and they are all adapted to this purpose provided they are not mixed with too large a proportion of sand and ferruginous clay, whereby they acquire a vitrescent texture in a high heat, and will not burn into lime. Limestone used to be calcined in a very rude kiln, formed by enclosing a circular space of 10 or 15 feet diameter, by rude stone walls 4 or 5 feet high, and filling the cylindrical cavity with alternate layers of turf or coal and limestone broken into moderate pieces. A bed of brushwood was usually placed at the bottom, to facilitate the kindling of the kiln. Whenever the combustion was fairly commenced, the top, piled into a conical form, was covered in with sods, to render the calcination slow and regular. This method being found relatively inconvenient and ineffectual, was succeeded by a permanent kiln built of stones or brickwork, in the shape of a truncated cone with the narrow end undermost, and closed at bottom by an iron grate. Into this kiln, the fuel and limestone were introduced at the top in alternate layers, beginning of course with the former; and the charge was either allowed to burn out, when the lime was altogether removed at a door near the bottom, or the kiln was successively fed with fresh materials, in alternate beds, as the former supply sunk down by the calcination, while the thoroughly burnt lime at the bottom was successively raked out by a side door immediately above the grate. The interior of the lime kiln has been changed of late years from the conical to the elliptical form; and probably the best is that of an egg placed with its narrow end undermost, and truncated both above and below; the ground plot or bottom of the kiln being compressed so as to give an elliptical section, with an eye or draft-hole towards each end of that ellipse. A kiln thus arched in above gives a reverberatory heat to the upper materials, and also favours their falling freely down in proportion as the finished lime is raked out below; advantages which the conical form does not afford. The size of the draft-notes for extracting the quicklime, should be proportionate to the size of the kiln, in order to admit a sufficient current of air to ascend with the smoke and flame, which is found to facilitate the extrication of the carbonic acid. The kilns are called perpetual, because the operation is carried on continuously as long as the building lasts; and draw-kilns, from the mode of discharging them by raking out the lime into carts placed against the draft-holes. Three bushels of calcined limestone, or lime-shells, are produced on an average for every bushel of coals consumed. Such kilns should be built up against the face of a cliff, so that easy access may be gained to the mouth for charging, by making a sloping cart road to the top of the bank.

Figs. 638, 639, 640, 641. represent the lime-kiln of Rüdersdorf near Berlin, upon the continuous plan, excellently constructed for economizing fuel. It is triple, and yields a threefold product. Fig. 640. is a view of it as seen from above; fig. 641., the elevation and general appearance of one side; fig. 638, a vertical section, and fig. 639. the ground plan in the line A B C D of fig. 638. The inner shaft fig. 638. has the form of two truncated cones, with their larger circular ends applied to each other; it has the greatest width at the level of the fire-door b, where it is 8 feet in diameter; it is narrower below at the discharge door, and at the top orifice, where it is about 6 feet in diameter. The interior wall d, of the upper shaft is built with hewn stones, to the height of 38 feet, and below that for 25 feet, with fire-bricks d´ d´, laid stepwise. This inner wall is surrounded with a mantle e, of limestones, but between the two there is a small vacant space of a few inches filled with ashes, in order to allow of the expansion of the interior with heat taking place without shattering the mass of the building.

The fire-grate b, consists of fire-tiles, which at the middle, where the single pieces press together, lie upon an arched support f. The fire-door is also arched, and is secured by fire-tiles. g is the iron door in front of that orifice. The tiles which form the grate have 3 or 4 slits of an inch wide for admitting the air, which enters through the canal h. The under part of the shaft from the fire to the hearth, is 7 feet, and the outer enclosing wall is constructed of limestone, the lining being of fire-bricks. Here are the ash-pit i, the discharge outlet a, and the canal k, in front of the outlet. Each ash-pit is shut with an iron door, which is opened only when the space i becomes filled with ashes. These indeed are allowed to remain till they get cool enough to be removed without inconvenience.

The discharge outlets are also furnished with iron doors, which are opened only for taking out the lime, and are carefully luted with loam during the burning. The outer walls l m n of the kiln, are not essentially necessary, but convenient, because they afford room for the lime to lie in the lower floor, and the fuel in the second. The several stories are formed of groined arches o, and platforms p, covered over with limestone slabs. In the third and fourth stories the workmen lodge at night. See fig. 641. Some enter their apartments by the upper door q; others by the lower door s. r is one of the chimneys for the several fire-places of the workmen. t u v are stairs.

As the limestone is introduced at top, the mouth of the kiln is surrounded with a strong iron balustrade to prevent the danger of the people tumbling in. The platform is laid with rails w, for the waggons of limestone, drawn by horses, to run upon. x is another rail-way, leading to another kiln. Such kilns are named after the number of their fire-doors, single, twofold, threefold, fourfold, &c.; from three to five being the most usual. The outer form of the kiln also is determined by the number of the furnaces; being a truncated pyramid of equal sides; and in the middle of each alternate side there is a fire-place, and a discharge outlet. A cubic foot of limestone requires for burning, one and five-twelfths of a cubic foot of wood, and one and a half of turf.

When the kiln is to be set in action, it is filled with rough limestones, to the height C D, or to the level of the firing; a wood fire is kindled in a, and kept up till the lime is calcined. Upon this mass of quicklime, a fresh quantity of limestones is introduced, not thrown in at the mouth, but let down in buckets, till the kiln be quite full; while over the top a cone of limestones is piled up, about 4 feet high. A turf-fire is now kindled in the furnaces b. Whenever the upper stones are well calcined, the lime under the fire-level is taken out, the superior column falls in, a new cone is piled up, and the process goes on thus without interruption, and without the necessity of once putting a fire into a; for in the space C B, the lime must be always well calcined. The discharge of lime takes place every 12 hours, and it amounts at each time in a threefold kiln, to from 20 to 24 Prussian tonnes of 6 imperial bushels each; or to 130 bushels imperial upon the average. It is found by experience, that fresh-broken limestone which contains a little moisture, calcines more readily than what has been dried by exposure for some time to the air; in consequence of the vapour of water promoting the escape of the carbonic acid gas; a fact well exemplified in distilling essential oils, as oil of turpentine and naphtha, which come over with the steam of water, at upwards of 100 degrees F. below their natural term of ebullition. Six bushels of Rüdersdorf quicklime weigh from 280 to 306 pounds.

When coals are used for fuel in a well-constructed perpetual, or draw kiln, about 1 measure of them should suffice for 4 or 5 of limestone.

The most extensive employment of quicklime is in agriculture, on which subject instructive details are given in Loudon’s Encyclopædias of Agriculture and Gardening.

Quicklime is employed in a multitude of preparations subservient to the arts; for clarifying the juice of the sugar-cane and the beet-root; for purifying coal gas; for rendering the potash and soda of commerce caustic in the soap manufacture, and in the bleaching of linen and cotton; for purifying animal matters before dissolving out their gelatine; for clearing hides of their hair in tanneries; for extracting the pure volatile alkali from muriate or sulphate of ammonia; for rendering confined portions of air very dry; for stopping the leakage of stone reservoirs, when mixed with clay and thrown into the water; for making a powerful lute with white of egg or serum of blood; for preparing a depilatory pommade with sulphuret of arsenic, &c. Lime water is used in medicine, and quicklime is of general use in chemical researches. Next to agriculture the most extensive application of quicklime is to MORTAR-CEMENTS, which see.

LINEN. See FLAX, and TEXTILE FABRICS.

LINSEED (Graine de lin, Fr.; Leinsame, Germ.); contains in its dry state, 11·265 of oil; 0·146 of wax; 2·488 of a soft resin; 0·550 of a colouring resinous matter; 0·926 of a yellowish substance analogous to tannin; 6·154 of gum; 15·12 of vegetable mucilage; 1·48 of starch; 2·932 of gluten; 2·782 of albumine; 10·884 of saccharine extractive; 44·382 of envelopes, including some vegetable mucilage. It contains also free acetic acid; some acetate, sulphate, and muriate of potash, phosphate and sulphate of lime; phosphate of magnesia; and silica. See OILS, UNCTUOUS.

LIQUATION (Eng. and Fr.; Saigerung, Germ.); is the process of sweating out, by a regulated heat, from an alloy, an easily fusible metal from the interstices of a metal difficult of fusion. Lead and antimony are the metals most commonly subjected to liquation; the former for the purpose of carrying off by a superior affinity the silver present in any complex alloy, a subject discussed under SILVER; the latter will be considered here, as referred to from the article ANTIMONY.

Figs. 642, 643, 644. represent the celebrated antimonial liquation furnaces of Malbosc, in the department of Ardèche, in France. Fig. 642. is a ground plan taken at the level of the draught holes g g, fig. 643., and of the dotted line E F; fig. 643. is a vertical section through the dotted line A B, of fig. 642.; and fig. 644. is a vertical section through the dotted line C D of fig. 642. In the three figures, the same letters denote like objects, a b c are three grates upon the same level above the floor of the works, 4-1/2 feet long, by 10-1/2 inches broad; between which are two rectangular galleries, d e, which pass transversely through the whole furnace, and lie at a level of 12 inches above the ground. They are separated by two walls from the three fire places. The walls have three openings, f g h, alternately placed for the flames to play through. The ends of these galleries are shut in with iron doors i i, containing peep holes. In each gallery are two conical cast-iron crucibles k k, into which the eliquating sulphuret of antimony drops. Their height is from 12 to 14 inches, the width of the mouth is 10 inches, that of the bottom is 6, and the thickness four-tenths of an inch. They are coated over with fire clay, to prevent the sulphuret from acting upon them; and they stand upon cast-iron pedestals with projecting ears, to facilitate their removal from the gallery or platform. Both of these galleries are lined with tiles of fire-clay l l, which also serve as supports to the vertical liquation tubes m m, made of the same clay. The tiles are somewhat curved towards the middle, for the purpose of receiving the lower ends of these tubes, and have a small hole at n, through which the liquid sulphuret flows down into the crucible.

The liquation tubes are conical, the internal diameter at top being 10 inches, at bottom 8; the length fully 40 inches, and the thickness six-tenths of an inch. They have at their lower ends notches or slits o, fig. 644., from 3 to 5 inches long, which look outwards, to make them accessible from the front and back part of the furnaces through small conical openings p p, in the walls. These are closed during the operation with clay stoppers, and are opened only when the gangue, rubbish, and cinders are to be raked out. The liquation tubes pass across the arch of the furnace q q, the space of the arch being wider than the tubes; they are shut in at top with fire-covers r r. s s, the middle part of the arch, immediately under the middle grate, is barrel-shaped, so that both arches are abutted together. The flames, after playing round about the sides of the liquation tubes, pass off through three openings and flues into the chimney t, about 13 feet high; u being the one opening, and v the two others, which are provided with register plates. In front of the furnace is a smoke flue w, to carry off the sulphureous vapours exhaled during the clearing out of the rubbish and slag; another x, begins over y y, at the top of the tubes; a wall z, separates the smoke flue into halves, so that the workmen upon the one side may not be incommoded by the fumes of the other. This wall connects at the same time the front flue w with the chimney t. a´ a´ and b´ b´ are iron and wooden bearer beams and rods for strengthening the smoke-flue, c´ c´ are arches upon both sides of the furnace, which become narrower from without inwards, and are closed with well-fitted plates d´ d´. They serve, in particular circumstances, to allow the interior to be inspected, and to see if either of the liquation furnaces be out of order.

Each tube being charged with about 500 lbs. of the antimonial ore, previously warmed upon the roof of the furnace, in a short time the sulphuret of a blue colour begins to flow out. Whenever the liquation ceases, the cinders are raked out by the side openings, and the tubes are charged afresh. The luted iron crucibles are suffered to become three-fourths full, are then drawn out from the galleries, left to cool, and emptied. The ingots weigh about 85 pounds. The charging is renewed every three hours, and, when the process is in good train, 100 lbs. of sulphuret of antimony are obtained every hour. The average duration of the tubes is 3 weeks, though in some cases it may be 40 days. The product from the ore is from 40 to 50 per cent. The above plan of operation is remarkable for the small consumption of fuel, the economy of labour, and the complete exhaustion of the ore.

LIQUEURS, LIQUORISTE; names given by the French to liquors compounded of alcohol, water, sugar, and different aromatic substances; and to the person who compounds them. I shall insert here a few of their most approved recipes.

Infusion of the peels of fruits.--The outer skin pared off with a sharp knife, is to be dropped into a hard glazed jar, containing alcohol of 34° B., diluted with half its bulk of water, and the whole is to be transferred into well-corked carboys. After an infusion of six weeks, with occasional agitation, the aromatized spirit is to be distilled off. In this way are prepared the liquors of cedrat, lemons, oranges, limettes (a sort of sweet lemon), poncires (the large citron), bergamots, &c.

Infusion of aromatic seeds.--These must be pounded, put into a carboy, along with alcohol diluted as above, infused with agitation for six weeks, and then distilled.

Infusions of aromatic woods are made in the same way.

The liquorist should not bring his infusions and tinctures into the market till six months after their distillation.

Liqueurs have different titles, according to their mode of fabrication.

Thus waters are liquors apparently devoid of viscidity; creams and oils possess it in a high degree.

Water of cedrat, is made by dissolving six pounds of sugar in seven quarts of water; adding two quarts of spirit of cedrat, and one of spirit of citron. Boil the whole for a minute, and filter hot through a proper bag. Set it for a considerable time aside in a corked carboy, before it be bottled.

Oil or cream of cedrat.--Take eight quarts of river water, two of spirit of cedrat, one of spirit of citron, and as much rich syrup as is necessary to give the mixture an oily consistence. Stir it well and set it aside in carboys. Should it be at all clouded, it must be filtered till it be perfectly pellucid.

Balm of Molucca, is made by infusing for ten days, in a carboy capable of holding fully four gallons, 10 pounds of spirits of 18° B., 4 pounds of white sugar, 4 pounds of river water, 4 drachms of pounded cloves, and 48 grains of pounded mace. The mixture is to be shaken 3 or 4 times daily, coloured with caramel (burnt sugar), filtered at the end of ten days, and set aside in bottles.

Tears of the widow of Malabar, are compounded with the preceding quantity of spirits, sugar, and water, adding 4 drachms of ground cinnamon, 48 grains of cloves, and a like quantity of mace, both in powder. It may be slightly coloured with caramel.

The delight of the Mandarins.--Take spirit, sugar, and water, as above, adding 4 drachms of anisum Chinæ, (Gingi), as much ambrette (seeds of the hibiscus abelmoschus, Lin.) all in powder; 2 drachms of safflower.

The sighs of love.--Take spirits, water, and sugar, as above. Perfume with essence (otto) of roses; give a very pale pink hue with tincture of cochineal, filter and bottle up.

Crème de macarons.--Add to the spirit, sugar, and water as above, half a pound of bitter almonds, blanched and pounded; cloves, cinnamon, and mace in powder, of each 48 grains. A violet tint is given by the tinctures of turnsole and cochineal.

Curaçoa.--Put into a large bottle nearly full of alcohol of trente-six (34° Baumé), the peels of six smooth Portugal oranges, (Seville?) and let them infuse for 15 days; then put into a carboy 10 pounds of spirits of 18° B., 4 pounds of white sugar, and 4 pounds of river water. When the sugar is dissolved, add a sufficient quantity of the orange zestes to give flavour, then spice the whole with 48 grains of cinnamon, and as much mace, both in powder. Lastly introduce an ounce of ground Brazil wood, and infuse during 10 days, agitating 3 or 4 times daily. A pretty deep hue ought to be given with caramel.

Swiss extract of wormwood, is compounded as follows:--

Tops of the absinthium majus 4 pounds; Ditto, absinthium minus 2 pounds; Roots of angelica, } Calamus aromaticus, } of each a few grains at pleasure; Seeds of anisum Chinæ, } Leaves of the dittany of Crete,} Alcohol of 20° B., four gallons Imp.

Macerate these substances during eight days, then distil by a gentle fire; draw off two gallons of spirits, and add to it 2 drachms of essential oil of anise-seed. The two gallons left in the still serve for preparing the vulnerary spirituous water.

Of colouring the liqueurs.

Yellow is given with the yellow colouring matter of safflower (carthamus,) which is readily extracted by water.

Fawn is given by caramel, made by heating ground white sugar in an iron spoon over a charcoal fire, till it assumes the desired tint, and then pouring it into a little cold water.

Red is given by cochineal alone, or with a little alum.

Violet is given by good litmus (turnsole).

Blue and green.--Sulphate of indigo gives the first. After saturating it nearly with chalk, alcohol being digested upon it, becomes blue. This tincture mixed with that of carthamus forms a good green.

LIQUID AMBER, is obtained from the liquidambar styraciflua, a tree which grows in Mexico, Louisiana, and Virginia. Some specimens are thin, like oil, and others are thickish, like turpentine. It is transparent, amber coloured, has an agreeable and powerful smell, and an aromatic taste, which feels pungent in the throat. Boiling alcohol dissolves it almost entirely. It contains a good deal of benzoic acid, some of which effloresces whenever the liquid amber hardens with keeping.

LITHARGE (Eng. and Fr.; Glätte, Germ.); is the fused yellow protoxide of lead, which on cooling passes into a mass consisting of small six-sided plates, of a reddish yellow colour, and semitransparent. It generally contains more or less red lead, whence the variations of its colour; and carbonic acid, especially when it has been exposed to the air for some. time. See LEAD, and SILVER, for its mode of preparation.

LITHIA, is a simple earthy or alkaline substance, discovered not many years ago, in the minerals called petalite and triphane. It is white, very caustic, reddens litmus, and red cabbage, and saturates acids with great facility. When exposed to the air it attracts humidity and carbonic acid. It is more soluble in water than baryta; and has such a strong affinity for it, as to be obtained only in the state of a hydrate. It forms neutral salts with all the acids. It is most remarkable for its power of acting upon, or corroding platinum.

LITHIUM, is the metallic basis of Lithia; the latter substance consists of 100 of metal, and 123 of oxygen.

LITHOGRAPHY. Though this subject belongs rather to the arts of taste and design than to productive manufactures, its chemical principles fall within the province of this Dictionary.

The term lithography is derived from λιθος, a stone, and γραφη, writing, and designates the art of throwing off impressions upon paper, of figures and writing previously traced upon stone. The processes of this art are founded:--

1. Upon the adhesion to a smoothly-polished limestone, of an encaustic fat which forms the lines or traces.

2. Upon the power acquired by the parts penetrated by this encaustic, of attracting to themselves, and becoming covered with a printer’s ink, having linseed oil for its basis.

3. Upon the interposition of a film of water, which prevents the adhesion of the ink in all the parts of the surface of the stone not impregnated with the encaustic.

4. Lastly, upon a pressure applied by the stone, such as to transfer to paper the greater part of the ink which covers the greasy tracings of the encaustic.

The lithographic stones of the best quality are still procured from the quarry of Solenhofen, a village at no great distance from Munich, where this mode of printing had its birth. They resemble in their aspect the yellowish white lias of Bath, but their geological place is much higher than the lias. Abundant quarries of these fine-grained limestones occur in the county of Pappenheim, along the banks of the Danube, presenting slabs of every required degree of thickness, parted by regular seams, and ready for removal with very little violence. The good quality of a lithographic stone is generally denoted by the following characters; its hue is of a yellowish gray, and uniform throughout; it is free from veins, fibres, and spots; a steel point makes an impression on it with difficulty; and the splinters broken off from it by the hammer, display a conchoidal fracture.

The Munich stones are retailed on the spot in slabs or layers of equal thickness; they are quarried with the aid of a saw, so as to sacrifice as little as possible of the irregular edges of the rectangular tables or plates. One of the broad faces is then dressed, and coarsely smoothed. The thickness of these stones is nearly proportional to their other dimensions; and varies from an inch and two-thirds to 3 inches.

In each lithographic establishment, the stones receive their finishing, dressing, and polishing; which are performed like the grinding and polishing of mirror plate. The work is done by hand, by rubbing circularly a movable slab over another cemented in a horizontal position, with fine sifted sand and water interposed between the two. The style of work that the stone is intended to produce, determines the kind of polish that it should get. For crayon drawing the stone should be merely grained more or less fine according to the fancy of the draughtsman. The higher the finish of the surface, the softer are the drawings; but the printing process becomes sooner pasty, and a smaller number of impressions can be taken. Works in ink require the stone to be more softened down, and finally polished with pumice and a little water. The stones thus prepared are packed for use with white paper interposed between their faces.

Lithographic crayons.--Fine lithographic prints cannot be obtained unless the crayons possess every requisite quality. The ingredients composing them ought to be of such a nature as to adhere strongly to the stone, both after the drawing has undergone the preparation of the acid, and during the press-work. They should be hard enough to admit of a fine point, and trace delicate lines without risk of breaking. The following composition has been successfully employed for crayons by MM. Bernard and Delarue, at Paris:--

Pure wax, (first quality) 4 Dry white tallow soap 2 White tallow 2 Gum lac 2 Lamp black, enough to give a dark tint 1 Occasionally copal varnish 1

The wax is to be melted over a gentle fire, and the lac broken to bits is then to be added by degrees, stirring all the while with a spatula; the soap is next introduced in fine shavings; and when the mixture of these substances is very intimately accomplished, the copal-varnish, incorporated with the lamp black, is poured in. The heat and agitation are continued till the paste has acquired a suitable consistence; which may be recognised by taking out a little of it, letting it cool on a plate, and trying its quality with a penknife. This composition, on being cut, should afford brittle slices. The boiling may be quickened by setting the rising vapours on fire, which increases the temperature, and renders the exhalations less offensive. When ready, it is to be poured into a brass mould, made of two semi-cylinders joined together by clasps or rings, forming between them a cylindric tube of the crayon size. The mould should be previously smeared with a greasy cloth.

M. Lasteyrie prescribes a more simple composition, said to be equally fit for the lithographer’s use:--

Dried white tallow soap 6 parts. White wax 6 -- Lamp black 1 --

The soap and tallow are to be put into a small goblet and covered up. When the whole is thoroughly fused by heat, and no clots remain, the black is gradually sprinkled in with careful stirring.

Lithographic ink is prepared nearly on the same principles:--

Wax 16 parts. Tallow 6 -- Hard tallow soap 6 -- Shell-lac 12 -- Mastic in tears 8 -- Venice turpentine 1 -- Lamp black 4 --

The mastic and lac, previously ground together, are to be heated with care in the turpentine; the wax and tallow are to be added after they are taken off the fire, and when their solution is effected, the soap shavings are to be thrown in. Lastly, the lamp black is to be well intermixed. Whenever the union is accomplished by heat, the operation is finished; the liquor is left to cool a little, then poured out on tables, and, when cold, cut into square rods.

Lithographic ink of good quality ought to be susceptible of forming an emulsion so attenuated, that it may appear to be dissolved when rubbed upon a hard body in distilled or river water. It should be flowing in the pen, not spreading on the stone; capable of forming delicate traces, and very black to show its delineations. The most essential quality of the ink is to sink well into the stone, so as to re-produce the most delicate outlines of the drawing, and to afford a great many impressions. It must therefore be able to resist the acid with which the stone is moistened in the preparation, without letting any of its greasy matter escape.

M. de Lasteyrie states that after having tried a great many combinations, he gives the preference to the following:--

Tallow soap, dried 30 parts. Mastic, in tears 30 -- White soda of commerce 30 -- Shell-lac 150 -- Lamp black 12 --

The soap is first put into the goblet and melted over the fire, to which the lac being added fuses immediately; the soda is then introduced, and next the mastic, stirring all the while with a spatula. A brisk fire is applied till all these materials be melted completely, when the whole is poured out into the mould.

The inks now prescribed may be employed equally with the pen and the hair pencil, for writings, black-lead drawings, aqua tinta, mixed drawings, those which represent engravings on wood (wood cuts), &c. When the ink is to be used it is to be rubbed down with water, in the manner of China ink, till the shade be of the requisite depth. The temperature of the place ought to be from 84° to 90° Fahr., or the saucer in which the ink-stick is rubbed should be set in a heated plate. No more ink should be dissolved than is to be used at the time, for it rarely keeps in the liquid state for 24 hours; and it should be covered or corked up.

Autographic paper.--Autography, or the operation by which a writing or a drawing is transferred from paper to stone, presents not merely a means of abridging labour, but also that of _re_verting the writings or drawings into the direction in which they were traced, whilst, if executed directly upon the stone, the impression given by it is _in_verted. Hence, a writing upon stone must be inverted from right to left to obtain direct impressions. But the art of writing thus is tedious and difficult to acquire, while, by means of the autographic paper and the transfer, proofs are obtained in the same direction with the writing and drawing.

Autographic ink.--It must be fatter and softer than that applied directly to the stone, so that though dry upon the paper, it may still preserve sufficient viscidity to stick to the stone by mere pressure.

To compose this ink, we take--

White soap 100 parts. White wax of the best quality 100 -- Mutton suet 30 -- Shell-lac 50 -- Mastic 50 -- Lamp black 30 or 35 --

These materials are to be melted as above described for the lithographic ink.

Lithographic ink and paper.--The following recipes have been much commended:

Virgin or white wax 8 parts White soap 2 -- Shell-lac 2 -- Lamp black 3 table-spoonsful.

Preparation.--The wax and soap are to be melted together, and before they become so hot as to take fire, the lamp black is to be well stirred in with a spatula, and then the mixture is to be allowed to burn for 30 seconds; the flame being extinguished, the lac is to be added by degrees, carefully stirring all the time; the vessel is to be put upon the fire once more in order to complete the combination, and till the materials are either kindled or nearly so. After the flame is extinguished, the ink must be suffered to cool a little, and then put into the moulds.

With the ink crayons thus made, lines may be drawn as fine as with the point of the graver, and as full as can be desired, without risk of its spreading in the carriage. Its traces will remain unchanged on paper for years before being transferred.

Some may think it strange that there is no suet in the above composition, but it has been found that ink containing it is only good when used soon after it is made, and when immediately transferred to the stone, while traces drawn on paper with the suet ink become defective after 4 or 5 days.

Lithographic paper.--Lay on the paper, 3 successive coats of sheep-feet jelly, 1 layer of white starch, 1 layer of gamboge.

The first layer is applied with a sponge dipped in the solution of the hot jelly, very equally over the whole surface, but thin; and if the leaf be stretched upon a cord, the gelatine will be more uniform. The next two coats are to be laid on, until each is dry. The layer of starch is then to be applied with a sponge, and it will also be very thin and equal. The coat of gamboge is lastly to be applied in the same way. When the paper is dry, it must be smoothed by passing it through the lithographic press; and the more polished it is, the better does it take on the ink in fine lines.

Transfer.--When the paper is moistened, the transfer of the ink from the gamboge is perfect and infallible. The starch separates from the gelatine, and if, after taking the paper off the stone, we place it on a white slab of stone, and pour hot water over it, it will resume its primitive state.

The coat of gamboge ought to be laid on the same day it is dissolved, as by keeping, it becomes of an oily nature; in this state it does not obstruct the transfer, but it gives a gloss to the paper which renders the drawing or tracing more difficult, especially to persons little habituated to lithography.

The starch paste can be employed only when cold, the day after it is made, and after having the skin removed from its surface.

A leaf of such lithographic paper may be made in two minutes.

In transferring a writing, an ink drawing, or a lithographic crayon, even the impression of a copper-plate, to the stone, it is necessary, 1. that the impressions be made upon a thin and slender body like common paper; 2. that they may be detached and fixed totally on the stone by means of pressure; but as the ink of a drawing sinks to a certain depth in paper, and adheres pretty strongly, it would be difficult to detach all its parts, were there not previously put between the paper and the traces, a body capable of being separated from the paper, and of losing its adhesion to it by means of the water with which it is damped. In order to produce this effect, the paper gets a certain preparation, which consists in coating it over with a kind of paste ready to receive every delineation without suffering it to penetrate into the paper. There are different modes of communicating this property to paper. Besides the above, the following may be tried. Take an unsized paper, rather strong, and cover it with a varnish composed of:--

Starch 120 parts Gum arabic 40 -- Alum 20 --

A paste of moderate consistence must be made with the starch and some water, with the aid of heat, into which the gum and alum are to be thrown, each previously dissolved in separate vessels. When the whole is well mixed, it is to be applied, still hot, on the leaves of paper, with a flat smooth brush. A tint of yellow colour may be given to the varnish, with a decoction of the berries of Avignon, commonly called French berries by our dyers. The paper is to be dried, and smoothed by passing under the scraper of the lithographic press.

Steel pens are employed for writing and drawing with ink on the lithographic stones.

LITMUS (Tournesol, Fr.; Lackmus, Germ.); is prepared in Holland from the species of lichen called Lecanora tartarea, Roccella tartarea, by a process which has been kept secret, but which is undoubtedly analogous to that for making archil and cudbear. The ground lichens are first treated with urine containing a little potash, and allowed to ferment, whereby they produce a purple-red; the coloured liquor, treated with quicklime and some more urine, is set again to ferment during two or three weeks, then it is mixed with chalk or gypsum into a paste, which is formed into small cubical pieces, and dried in the shade. Litmus has a violet-blue colour, is easy to pulverize, is partially soluble in water and dilute alcohol, leaving a residuum consisting of carbonate of lime, of clay, silica, gypsum, and oxide of iron combined with the dye. The colour of litmus is not altered by alkalis, but is reddened by acids; and is therefore used in chemistry as a delicate test of acidity, either in the state of solution or of unsized paper stained with it. It is employed to dye marble blue.

LIXIVIATION (Lessivage, Fr.; Auslagen, Germ.); signifies the abstraction by water of the soluble alkaline or saline matters present in any earthy admixture; as from that of quicklime and potashes to make potash lye, from that of effloresced alum schist to make aluminous liquors, &c.

LOADSTONE, MAGNETIC IRON-STONE (Fer oxydulé, Fr.; Magneteisenstein, Germ.); an iron ore consisting of the protoxide and peroxide of iron in a state of combination.

LOAM (Terre-limoneuse, Fr.; Lehm, Germ.); a native clay mixed with quartz sand and iron ochre, and occasionally with some carbonate of lime.

LODE, is the name given by the Cornish miners to a vein, whether it be filled with metallic or earthy matter.

LOGWOOD (Bois de Campèche, Bois bleu, Fr.; Blauholz, Germ.); is the wood of the Hæmatoxylon Campechianum, a native tree of central America, grown in Jamaica since 1715. It was first introduced into England in the reign of Elizabeth, but as it afforded to the unskilful dyers of her time a fugitive colour, it was not only prohibited from being used, under severe penalties, but was ordered to be burned wherever found, by a law passed in the 23d year of her reign. The same prejudice existed, and the same law was enacted against indigo. At length, after a century of absurd prohibition, these two most valuable tinctorial matters, by which all our hats, and the greater part of our woollen cloths, are dyed, were allowed to be used.

Old wood, with black bark and with little of the white alburnum, is preferred. Logwood is denser than water, very hard, of a fine compact grain, and almost indestructible by the atmospheric elements; it has a sweet and astringent taste, and a peculiar not inoffensive smell.

For its chemical composition, see HEMATIN.

When chipped logwood is for some time exposed to the air, it loses a portion of its dyeing power. Its decoction absorbs the oxygen of the atmosphere, and then acquires the property of precipitating with gelatine, which it had not before. The dry extract of logwood, made from an old decoction, affords only a fugitive colour.

For its applications in dyeing, see BLACK DYE; BROWN DYE; CALICO PRINTING; DYEING; HAT DYEING, &c.

The imports of logwood for home use, were, in 1836, 12,880 tons, 13 cwts.; in 1837, 14,677 tons, 13 cwts. And the amount of duty received was, in 1836, 2,480_l._; in 1837, 2,552_l._

LOOM (Metier a tisser, Fr.; Weberstuhl, Germ.); is the ancient and well-known machine for weaving cloth by the decussation of a series of parallel threads, which run lengthwise, called the warp or chain, with other threads thrown transversely with the shuttle, called the woof or weft. See JACQUARD LOOM and WEAVING.

LUBRICATION. The following simple and efficacious plan of lubricating the joints and bearings of machinery by capillary attraction, has been kindly communicated to me, by its ingenious inventor, Edward Woolsey, Esq.:--

Fig. 645. represents a tin cup, which has a small tin tube A, which passes through the bottom, as shown by the dotted lines. It may have a tin cover to keep out the dust.

Fig. 646. is a plan of the same.

Fig. 647. is a section of the same. Oil is poured into the cup, and one end of a worsted or cotton thread is dipped into the oil, and the other end passed through the tube. The capillary attraction causes the oil to ascend and pass over the orifice of the tube, whence it gradually descends, and drops slower or quicker, according to the length of the thread, or its thickness, until every particle of oil is drawn over by this capillary syphon. The tube is intended to be put into the bearings of shafts, &c., and is made of any size that may be wished. If oil, or other liquids, is desired to be dropped upon a grindstone or other surface, this cup can have a handle to it, or be hung from the ceiling.

Fig. 648. It is frequently required to stop the capillary action when the machinery is not going; and this has been effected by means of a tightening screw, which passes through a screw boss in the cover of the cup, and presses against the internal orifice of the tube, preventing the oil from passing.

Fig. 649. As I find when these screw cups (fig. 648.) are used upon beams of engines and moving bearings, that the screw is apt to be tightened by the motion; and also, as I think the action of the screw is uncertain, from the workman neglecting to screw it down sufficiently, it answers best to take out the capillary thread when the lubrication is not required; and to effect this easily, I have a tin top to the cup, with a round pipe soldered to it: this pipe has a slit in it, like a pencil case, and allows a bolt B to slide easily in it. In fig. 650. the bolt is down; in fig. 651., the bolt, which is a piece of brass wire, is drawn up, and there is no capillary action between the thread and the oil. In fig. 651. it will be observed, that the bolt is kept in its place by its head C, resting in a lateral slit in the pipe, and it cannot be drawn out on account of the pin E. One end of the thread is fastened to the eye-hole at the bottom of the bolt, and the other end is tied to a small wire which crosses the lower orifice of the tube at D and which is shown in plan fig. 652.

By this simple contrivance the capillary action can be stopped or renewed in a second, without removing the top of the lubricator.

The saving by this plan, instead of pouring oil into the bearings, is 2 gallons out of 3, while the bearings are better oiled.

“I send you the drawings of the lubricators, with a detailed explanation. I have omitted to state, that the saving in labour is considerable where there are many joints to keep oiled three or four times a day; and that the workman does not, with this apparatus, run the risk of being caught by the machinery. Perhaps your friends may be at a loss how to tie on the cotton or worsted thread. I pass a long thread through the eye-hole E of the bolt, and then draw the two ends through the tube by a fine wire with a hook to it, one end on one side of the cross wire D, and the other end on the other side. I then put the cover on, and the bolt in the position shown in fig. 651.; when by drawing the two ends of the thread, and tying them across the wire D, you have the exact length required. When you wish to see the quantity of oil remaining in the lubricator, the bolt must be dropped as in fig. 650., and you can then lift the cover a little way off, without breaking the thread, and replenish with oil. The cost of fig. 650. in tin plate is 9_d._ The figures in the wood cuts are one third of the full size.

“Believe me to be yours sincerely,

“E. J. WOOLSEY.”

LUPININE, is a substance of a gummy appearance, so named by M. Cussola, because it was obtained from Lupines.

LUPULINE, from Humulus Lupulus; is the peculiar bitter aromatic principle of the hop. See BEER.

LUTE (from lutum, clay; Lut, Fr.; Kitte, Beschläge, Germ.); is a pasty or loamy matter employed to close the joints of chemical apparatus, or to coat their surfaces, and protect them from the direct action of flame. Lutes differ according to the nature of the vapours which they are destined to confine, and the degree of heat which they are to be exposed to.

1. Lute of linseed meal, made into a soft plastic dough with water, and immediately applied pretty thick to junctions of glass, or stone-ware, makes them perfectly tight, hardens speedily, resists acid and ammoniacal vapours, as also a moderate degree of heat. It becomes stronger when the meal is kneaded with milk, lime-water, or solution of glue.

2. Lute of thick gum-water, kneaded with clay, and iron filings, serves well for permanent junctions, as it becomes extremely solid.

3. By softening in water a piece of thick brown paper, kneading it first with rye-flour paste, and then with some potter’s clay, till it acquire the proper consistence, a lute is formed which does not readily crack or scale off.

4. Lute, consisting of a strong solution of glue kneaded into a dough with new slaked lime, is a powerful cement, and with the addition of white of egg, forms the lut d’ane;--a composition adapted to mend broken vessels of porcelain and stone-ware.

5. Skim-milk cheese, boiled for some time in water, and then triturated into paste with fresh-slaked lime, forms also a good lute.

6. Calcined gypsum, diffused through milk, solution of glue or starch, is a valuable lute, in many cases.

7. A lute made with linseed, melted caoutchouc, and pipe-clay, incorporated into a smooth dough, may be kept long soft when covered in a cellar, and serves admirably to confine acid vapours. As it does not harden, it may therefore be applied and taken off as often as we please.

8. Caoutchouc itself, after being melted in a spoon, may be advantageously used for securing joints against chlorine and acid vapours, in emergencies when nothing else would be effectual. It bears the heat at which sulphuric acid boils.

9. The best lute for joining crucibles inverted into each other, is a dough made with a mixture of fresh fire-clay, and ground fire-bricks, worked with water. That cement if made with solution of borax answers still better, upon some occasions, as it becomes a compact vitreous mass in the fire. See CEMENTS.

LUTEOLINE, is a yellow colouring matter discovered by Chevreul in weld. When sublimed, it crystallizes in needles.

LYCOPODIUM CLAVATUM. The seeds of the lycopodium ripen in September. They are employed, on account of their great combustibility, in theatres, to imitate the sudden flash of lightning, by throwing a quantity of them from a powder puff, or bellows, across the flame of a candle.

LYDIAN STONE, is flint-slate.

M.

MACARONI, is a dough of fine wheat flour, made into a tubular or pipe form, of the thickness of goose-quills, which was first prepared in Italy, and introduced into commerce under the name of Italian or Genoese paste. The wheat for this purpose must be ground into a coarse flour, called gruau or semoule, by the French, by means of a pair of light mill-stones, placed at a somewhat greater distance than usual. This semoule is the substance employed for making the dough. For the mode of manufacturing it into pipes, see VERMICELLI.

MACE, is a somewhat thick, tough, unctuous membrane, reticulated or chapt, of a yellowish-brown or orange colour. It forms the envelop of the shell of the fruit of the myristica moschata, which contains the nutmeg. It is dried in the sun, after being dipped in brine; sometimes it is sprinkled over with a little brine, before packing, to prevent the risk of moulding. Mace has a more agreeable flavour than nutmeg; with a warm and pungent taste. It contains two kinds of oil; the one of which is unctuous, bland, and of the consistence of butter; the other is volatile, aromatic, and thinner. The membrane is used as a condiment in cookery, and the aromatic oil in medicine.

MACERATION (Eng. and Fr.; Einweichen, Germ.), is a preparatory steep to which certain vegetable and animal substances are submitted, with the view of distending their fibres or pores, and causing them to be penetrated by such menstrua as are best adapted to extract their soluble parts. Water, alone, or mixed with acids, alkalis, or salts; alcohol and ether, are the liquids usually employed for that purpose.

MACLE, is the name of certain diagonal black spots in minerals, like the ace of diamonds in cards, supposed to proceed from some disturbance of the particles in the act of crystallization.

MADDER (Garance, Fr.; Färberröthe, Germ.), a substance very extensively used in dyeing, is the root of the Rubia tinctorum, a plant, of which two species are distinguished by Linnæus.

The best roots are those which have the size of a writing quill, or, at most, of the little finger. They are semitransparent, and reddish; have a strong odour, and a smooth bark. They should be of two or three years’ growth.

The madder, taken from the ground and picked, must be dried in order to be ground and preserved. In warm climates it is dried in the open air; but, elsewhere, stoves must be employed.

The stringy filaments and epidermis are to be removed, called mulle; as also the pith, so as to leave nothing but the ligneous fibres.

The preparation of madders is carried on in the department of the Rhone, in the following manner.

The roots are dried in a stove, heated by means of a furnace, from which the air is allowed to issue only at intervals, at the moment when it is judged to be saturated with moisture. The furnace-flue occupies a great portion of the floor; above are three close gratings, on which the roots are distributed in layers of about two decimetres (nearly 8 inches). At the end of 24 hours, those which are on the first grated floor directly above the stove are dry, when they are taken away and replaced by those of the superior floors. This operation is repeated whenever the roots over the stove are dry. The dry roots are thrashed with a flail, passed through fanners similar to those employed for corn, and then shaken upon a very coarse sieve. What passes through is farther winnowed and sifted through a finer sieve than the first. These operations are repeated five times, proceeding successively to sieves still finer and finer, and setting aside every time what remains on the sieve. What passes through the fifth sieve is rejected as sand and dust. After these operations, the whole fibrous matters remaining on the sieve are cleaned with common fanners, and women separate all the foreign matters which had not been removed before. For dividing the roots, afterwards, into different qualities, a brass sieve is made use of, whose meshes are from six to three millimetres in diameter (from 1/4th to 1/8th inch E.) What passes through the finest is rejected; and what passes through the coarsest is regarded as of the best quality. These roots thus separated, are carried into a stove, of a construction somewhat different from the first. They are spread out in layers of about a decimetre in thickness (nearly 4 inches E.), on large lattice-work frames, and the drying is known to be complete, when on taking up a handful and squeezing it, the roots break easily. On quitting the stove, the madder is carried, still hot, into a machine, where it is minced small, and a sieve separates the portion of the bark reduced to powder. This operation is repeated three or four times, and then the boulter is had recourse to. What passes through the sieve, or the brass meshes of the boulter, is regarded as common madder; and what issues at the extremity of the boulter is called the flour. Lastly, the madder which passes through the boulter is ground in a mill with vertical stones, and then passed through sieves of different sizes. What remains above is always better than what goes through.

The madder of Alsace is reduced to a very fine powder, and its colouring matter is extracted by a much longer ebullition than is necessary for the lizari of the Levant. The prepared madders ought to be carefully preserved from humidity, because they easily imbibe moisture, in which case fermentation spoils their colour.

D’Ambourney and Beckman have asserted, that it is more advantageous to employ the fresh root of madder than what has been submitted to desiccation, especially by means of stoves. But in its states of freshness, its volume becomes troublesome in the dyeing bath, and uniform observation seems to prove that it ameliorates by age. Besides, it must be rendered susceptible of keeping and carrying easily.

It appears that madder may be considered as composed of two colouring substances, one of which is dun (tawny), and the other is red. Both of these substances may combine with the stuff. It is of consequence, however, to fix only the red part. The dun portion appears to be more soluble, but its fixity on stuffs may possibly be increased by the affinity which it has for the red portion.

The different additions made to madder, and the multiplied processes to which it is sometimes exposed, have probably this separation for their chief object.

The red portion of madder is soluble, but in small quantity, in water. Hence but a limited concentration can be given to its solution. If the portion of this substance be too much increased, so far from obtaining a greater effect, we merely augment the proportion of the dun part, which is the more soluble of the two.

In consequence of the Société Industrielle of Mulhausen having offered in the year 1826 large premiums to the authors of the best analytical investigation of madder, eight memoirs were transmitted to it in the year 1827. They were examined with the greatest care by a committee consisting of able scientific and practical men. None of the competitors however fulfilled the conditions of the programme issued by the society; but four of them received a tribute of esteem and gratitude from it; MM. Robiquet and Colin at Paris, Kuhlmann at Lille, and Houton-Libillardière. Fresh premiums were offered for next year, to the amount of 2000 francs.

Every real discovery made concerning this precious root, would be of vast consequence to dyers and calico-printers. Both M. Kuhlmann, and Robiquet and Colin, conceived that they had discovered a new principle in madder, to which they gave the name alizarine. The latter two chemists treated the powdered madder with sulphuric acid, taking care to let it heat as little as possible. By this action the whole is carbonized, except perhaps the red matter. The charcoal thus obtained is pulverized, mixed with water, thrown upon a filter, and well washed in the cold. It is next dried, ground, and diffused through fifty parts of water, containing six parts of alum. This mixture is then boiled for one quarter of an hour, and thrown upon a filter cloth while boiling hot. The residuum is once more treated with a little warm alum water. The two liquors are to be mixed, and one part of sulphuric acid poured into them; when they are allowed to cool with occasional agitation. Flocks now make their appearance; the clear liquid is decanted, and the grounds are thrown upon a filter. The precipitate is to be washed, first with acidulated water, then with pure water, and dried, when the colouring matter is obtained in a red or purple state. This purple substance, when heated dry, gives out alizarine, and an empyreumatic oil, having an odour of animal matter; while a charcoally matter remains.

M. Dan. Kœchlin, the justly celebrated calico-printer of Mulhausen, has no faith in alizarine as the dyeing principle of madder; and thinks moreover that, were it of value, it could not be extracted on the great scale, on account of the destructive heat which would result from the acid acting upon a considerable body of the ground madder. Their alizarine is not a uniform substance, as it ought to be, if a proximate principle; for samples of it obtained in different repetitions of the process have produced very variable effects in dyeing. The madders of Avignon, though richer in colour than those of Alsace, afford however little or no alizarine. In fact, purpurine, the crude substance from which they profess to extract alizarine, is a richer dye than this pure substance itself.

Madder contains so beautiful and so fast a colour, that it has become of almost universal employment in dyeing; but that colour is accompanied with so many other substances which mask and degrade it, that it can be brought out and fixed only after a series of operations more or less difficult and precarious. This dye is besides so little soluble, that much of it is thrown away in the dye-house; the portion supposed to be exhausted being often as rich as other fresh madder; hence it would be a most valuable improvement in this elegant art to insulate this tinctorial body, and make it a new product of manufacture.

Before the time of Haussmann, an apothecary at Colmar, the madder bath was subject to many risks, which that skilful chemist taught dyers how to guard against, by introducing a certain quantity of chalk into the bath. A change of residence led Haussmann to this fortunate result. After having made very fine reds at Rouen, he encountered the greatest obstacles in dyeing the same reds at Logelbach near Colmar, where he went to live. Numerous trials, undertaken with the view of obtaining the same success in his new establishment, proved that the cause of his favourable results at Rouen existed in the water, which contained carbonate of lime in solution, whilst the water of Logelbach was nearly pure. He then tried a factitious calcareous water, by adding chalk to his dye bath. Having obtained the most satisfactory results, he was not long of producing here as beautiful and as solid reds as he had done at Rouen. This practice became soon general among the calico-printers of Alsace, though in many dye-works the chalk is now replaced by lime, potash, or soda. But when the madder of Avignon is used, all these antacid correctives become unnecessary, because it contains a sufficient quantity of carbonate of lime; an important fact first analytically demonstrated by that accurate chemist M. Henri Schlumberger of Mulhausen. Avignon madder indicates the presence of carbonate of lime in it, by effervescing with dilute acids, which Alsace madder does not.

M. Kuhlmann found a free acid resembling the malic, in his analysis of madders. But his experiments were confined to those of Alsace. The madders of Avignon are on the contrary alkaline, as may be inferred from the violet tint of the froth of their infusions; whereas that of the Alsace madders is yellowish, and it strongly reddens litmus paper. This important difference between the plants of these two districts, depends entirely upon the soil; for madders grown in a calcareous shelly soil in Alsace, have been found to be possessed of the properties of the Avignon madder.

The useful action of the carbonate and the phosphate of lime in the madder of Avignon, explains why madders treated with acids which remove their calcareous salts, without taking away their colouring matter, lose the property of forming fast dyes. Many manufacturers are in the habit of mixing together, and with advantage, different sorts of madder. That of Avignon contains so much calcareous matter that, when mixed with the madder of Alsace, it can compensate for its deficiency. Some of the latter is so deficient as to afford colours nearly as fugitive as those of Brazil wood and quercitron. The Alsace madders by the addition of chalk to their baths, become as fit for dyeing Turkey reds as those of Avignon. When the water is very pure, one part of chalk ought to be used to five of Alsace madder, but when the waters are calcareous, the chalk should be omitted. Lime, the neutral phosphate of lime, the carbonate of magnesia, oxide and carbonate of zinc, and several other substances have the property of causing madder to form a fast dye, in like manner as the carbonate of lime.

The temperature of from 50° to 60° R. (145° to 167° F.), is the best adapted to the solution of the colouring matter, and to its combination with the mordants; and thus a boiling heat may be replaced advantageously by the long continuance of a lower temperature. A large excess of the dye-stuff in the bath is unfavourable in two points of view; it causes a waste of colouring matter, and renders the tints dull. It is injurious to allow the bath to cool, and to heat it again.

In a memoir published by the Society of Mulhausen, in September, 1835, some interesting experiments upon the growth of madders in factitious soils are related by MM. Kœchlin, Persoz, and Schlumberger. A patch of ground was prepared containing from 50 to 80 per cent. of chalky matter, and nearly one fifth of its bulk of good horse-dung. Slips of Alsace and Avignon madders were planted in March, 1834, and a part of the roots were reaped in November following. These roots, though of only six months growth, produced tolerably fast dyes, nor was any difference observable between the Alsace and the Avignon species; whilst similar slips or cuttings, planted in a natural non-calcareous soil, alongside of the others, yielded roots which gave fugitive dyes. Others were planted in the soil of Palud, transported from Avignon, which contained more than 90 per cent. of carbonate of lime, and they produced roots that gave still faster dyes than the preceding. Three years are requisite to give the full calcareous impregnation to the indigenous madders of Avignon.

As to the function of the chalk, valuable observations, made long ago by M. Daniel Kœchlin, have convinced him, that the combination of two different bases with a colouring matter, gave much more solidity to the dye, in consequence, undoubtedly, of a greater insolubility in the compound. Experiments recently made by him and his colleagues above named, prove that in all cases of madder-dyeing under the influence of chalk, a certain quantity of lime becomes added to the aluminous mordant. In the subsequent clearing with a soap bath, some of the alumine is removed, and there remains upon the fibre of the cloth a combination of these two earths in atomic proportions. Thus the chalk is not for the purpose of saturating the acid, as had been supposed, but of forming a definite compound with alumina, and probably also with the fatty bodies, and the colouring matter itself.

The red mordants are prepared commonly in Alsace, as follows:--The crushed alum and acetate of lead being weighed, the former is put into a deep tub, and dissolved by adding a proper quantity of hot water, when about one tenth of its weight of soda crystals is introduced to saturate the excess of acid in the alum. The acetate of lead is now mixed in; and as this salt dissolves very quickly, the reaction takes place almost instantly. Care must be taken to stir for an hour. The vessel should not be covered, lest its contents should cool too slowly.

The different mordants most generally employed for madder, are detailed under Colours, in CALICO-PRINTING and MORDANT.

Much mordant should not be prepared at once, for sooner or later it will deposit some sub-acetate of alumina. This decomposition takes place even in corked phials in the cold; and the precipitate does not readily dissolve again in acetic acid. All practical men know that certain aluminous mordants are decomposed by heating them, and restored on cooling, as Gay Lussac has pointed out. He observed, that by adding to pure acetate of alumina, some alum or sulphate of potash, the mixture acquires the property of forming a precipitate with a heat approaching the boiling point, and of redissolving on cooling. The precipitate is alumina nearly pure, according to M. Gay Lussac; but, by M. Kœchlin’s more recent researches, it is shown to be sub-sulphate of alumina, containing eight times as much base as the neutral sulphate.

Madder dye.--On account of the feeble solubility of its colouring matter in water, we cannot dye with its decoction; but we must boil the dye-stuff along with the goods to be dyed; thereby the water dissolves fresh portions of the dye, and imparts it in succession to the textile fibres. In dyeing with madder, we must endeavour to fix as little of the dun matter as possible upon the cloth.

Dyeing on wool.--Alumed wool takes, in the madder bath, a red colour, which is not so bright as cochineal red, but it is faster; and as it is far cheaper, it is much used in England to dye soldiers cloth. A mordant of alum and tartar is employed; the bath of madder, at the rate of from 8 to 16 ounces for the pound of cloth, is heated to such a degree that we can just hold our hand in it, and the goods are then dyed by the wince, without heating the bath more till the colouring matter be fixed. Vitalis prescribes as a mordant, one fourth of alum, and one sixteenth of tartar; and for dyeing, one third of madder, with the addition of a 24th of solution of tin diluted with its weight of water. He raises the temperature in the space of an hour, to 200°, and afterwards he boils for 3 or 4 minutes; a circumstance which is believed to contribute to the fixation of the colour. The bath, after dyeing, appears much loaded with yellow matter, because this has less affinity for the alum mordant than the red. Sometimes a little archil is added to the madder, to give the dye a pink tinge; but this is fugitive.

Silk is seldom dyed with madder, because cochineal affords brighter tints.

Dyeing on cotton and linen.--The most brilliant and fastest madder red is the Turkey or Adrianople. The common madder reds are given in the following way:--The yarn or cloth is boiled in a weak alkaline bath, washed, dried and galled, by steeping the cotton in a decoction of bruised galls or of sumach. After drying, it is twice alumed; for which purpose, for every 4 parts of the goods, one part of alum is taken, mixed with 1-16th of its weight of chalk. The goods are dipped into a warm solution of the alum, wrung out, dried, and alumed afresh, with half the quantity. The acetate of alumina mordant, described above, answers much better than common alum for cotton. After the goods are dried and rinsed, they are passed through the dye bath, which is formed of 3/4 lb. of good madder for every pound of cotton; and it is raised to the boiling point by degrees, in the space of 50 or 60 minutes. Whenever the ebullition has continued a few minutes, the goods must be removed, washed slightly, and dyed a second time in the same way, with as much madder. They are then washed and passed through a warm soap bath, which removes the dun colouring matter.

Hölterhoff prescribes for ordinary madder red the following proportions:--20 pounds of cotton yarn; 14 pounds of Dutch madder; 3 pounds of nut-galls; 5 pounds of alum; to which 1/2 lb. of acetate of lead has been first added, and then a quarter of a pound of chalk.

In the calico-print works the madder goods are passed through a bran bath first, immediately after dyeing; next, after several days exposure to the air, when the dun dye has become oxidized, and is more easily removed. An addition of chalk, on the principles explained above, is sometimes useful in the madder bath. If bran be added to the madder bath, the colour becomes much lighter, and of an agreeable shade. Sometimes bran-water is added to the madder bath, instead of bran.

Adrianople or Turkey red.--This is the most complicated and tedious operation in the art of dyeing; but it produces the fastest colour which is known. This dye was discovered in India, and remained long a process peculiar to that country. It was afterwards practised in other parts of Asia and in Greece. In 1747, Ferquet and Goudard brought Greek dyers into France, and mounted near Rouen, and in Languedoc, Turkey-red dye works. In 1765, the French government, convinced of the importance of this business, caused the processes to be published. In 1808, Reber, at Mariakirch, furnished the finest yarn of this dye, and M. Köchlin became celebrated for his Turkey-red cloth.

Process for Turkey-red.--The first step consists in clearing the yarn or cloth in alkaline baths, and dipping them in oily liquors, to which sheep’s dung was formerly added. This operation is repeated several times, the goods being dried after each immersion. There next follows the cleansing with alkaline liquors to remove the excess of oil, the galling, the aluming, the maddering, the brightening or removing the dun part of the dye by boiling, at a high temperature, with alkaline liquid, and the rosing by boiling in a bath of salt of tin. We shall give some details concerning this tedious manipulation, and the differences which exist in it in the principal dye-works.

At Rouen, where the process was first brought to perfection, two methods are pursued, called the gray and the yellow course or march. In the gray, the dye is given immediately after the cotton has received the oily mordant, the gall, and the alum, as it has then a gray colour. In the yellow course, it is passed through fresh oils, alum, and galls before the maddering, the cotton having then a yellow tint.

Different views have been taken of the principles of the Turkey red dye, and the object and utility of the various steps. The most ancient notion is that of animalizing the cotton by dung and blood, but experience has proved that without any animal matter the finest colour may be obtained. According to Dingler, the cotton is imbued with oil by steeping it in combinations of oil and soda; the oil is altered by repeated dryings at a high temperature; it attracts oxygen from the air, and thereby combines intimately with the cotton fibre, so as to increase the weight of the stuff. The dung, by a kind of fermentation, accelerates the oxidizement, and hence crude oil is preferable to pure. In England, the mucilaginous oils of Gallipoli are preferred, and in Malabar, oils more or less rancid. The drying oils do not answer. The subsequent treatment with the alkaline liquors removes the excess of oil, which has not been oxidized and combined; a hard drying completely changes that which remains in the fibres; the aluming which follows combines alumina with the cotton; the galling tans the fibres, producing a triple compound of oil and alum, which fixes the colouring matter. The object of the other steps is obvious.

According to Wuttich the treatment with oil opens the cotton so as to admit the mordant and the colouring matter, but the oil and soap do not combine with the fibres. In the alkaline baths which follow, the oil is transformed into soap and removed; whence the cotton should not increase in weight in the galling and aluming; the cotton suffers a kind of tanning, and the saline parts of the blood assist in fixing the madder dye.

The German process improved, according to Dingler, consists of the following operations: mordant of an oily soap or a soapy liniment, hard drying; alkaline bath, drying, steeping, rinsing away of the uncombined mordant, drying; galling, drying; aluming, drying, steeping in water containing chalk, rinsing; maddering, airing, rinsing; brightening with an alkaline boil, and afterwards in a bath containing salt of tin; then washing and drying.

The yarn or the cloth must be first well worked in a bath of sheep’s dung and oil, compounded as follows:--25 pounds of sheep’s dung are to be bruised in a solution of pure caustic potash of hydrometer strength 3°, and the mixed liquor is to be passed through a sieve. Two pounds of fine oil are now to be poured into 16 pounds of this lye, after which 30 pounds of coarse oil are to be added, with agitation for 1/4 of an hour. Other 4 pounds of hot lye are to be well stirred in, till the whole is homogeneous. This proportion of mordant is sufficient for 100 pounds of cotton yarn, for 90 pounds of unbleached or 100 pounds of bleached cotton goods. The cotton stuff, after being well wrung out, is to be laid in a chest and covered with a lid loaded with weights, in which state it should remain for five days. At the end of 24 hours, the cotton becomes hot with fermentation, gets imbued with the mordant, and the oil becomes rapidly altered. The goods are next exposed freely to the air during the day, and in the evening they are dried in a hot chamber, exposed to a temperature of 158° F., for 6 or 8 hours, which promotes the oxidizement of the oil.

The goods are now passed the second time through a soapy-oil mordant similar to the first, then dried in the air by day, and in the hot stove by night. The third and fourth oil-soap steeps are given in the same way, but without the dung. The fifth steep is composed of a lye at 2°, after which the goods must also be dried. Indeed from the first to the fourth steep, the cotton stuff should be put each time into a chamber heated to 145° F. for 12 or 15 hours, and during 18 hours after the fifth steep.

The uncombined oil must, in the next place, be withdrawn by the degraissage, which consists in steeping the goods for 6 hours in a very weak alkaline ley. After rinsing and wringing, they are dried in the air, and then put into the hot stove.

The goods are now galled in a bath formed of 36 pounds of Sicilian sumach, boiled for 3 hours in 260 pounds of water, and filtered. The residuum is treated with 190 fresh pounds of water. This decoction is heated with 12 pounds of pounded nut-galls to the boiling point, allowed to cool during the night, and used next morning as hot as the hand can bear; the goods being well worked through it. They are again dried in the air, and afterwards placed in a stove moderately heated. They are next passed through a tepid alum bath, containing a little chalk; left afterwards in a heap during the night, dried in the air, and next in the stove. The dry goods are finally passed through hot water containing a little chalk, wrung out, rinsed, and then maddered.

For dyeing, the copper is filled with water, the fire is kindled, and an ounce and a half of chalk is added for every pound of madder; a pound and a quarter of madder being taken for every pound of cotton yarn. The goods are now passed through the bath, so that they penetrate to near its bottom. The fire must be so regulated, that the copper will begin to boil in the course of from 2-1/2 to 3 hours; and the ebullition must be continued for an hour; after which the yarn is aired and rinsed. Cloth should be put into the dye-bath when its temperature is 77°, and winced at a heat of from 100° to 122° during the first hour; at 167° during the second; and at the boiling point when the third hour begins. It is to be kept boiling for half an hour; so that the maddering lasts four hours. Dingler does not add sumach or galls to the madder bath, because their effect is destroyed in the subsequent brightening, and he has no faith in the utility of blood.

After being dyed, the goods are washed, pressed, and subjected to a soapy alkaline bath at a high heat, in a close boiler, by which the dun parts of the galls and the madder are dissolved away, and the red colour remains in all its lustre. This operation is called brightening. It is repeated in a similar liquor, to which some muriate of tin is added for the purpose of enlivening the colour and giving it a rosy tint. Last of all, the goods are rinsed, and dried in the shade.

The Elberfeld process consists for 100 libs. of the following steps:--

1. Cleaning the cotton by boiling it for four hours in a weak alkaline bath, cooling and rinsing.

2. Working it thoroughly four times over in a steep, consisting of 300 pounds of water, 15 pounds of potash, 1 pailful of sheep’s dung, and 12-1/2 pounds of olive oil, in which it should remain during the night. Next day it is drained for an hour, wrung out and dried. This treatment with the dung steep, and drying, is repeated 3 times.

3. It is now worked in a bath containing 120 quarts of water, 18 pounds of potash, and 6 quarts of olive oil; then wrung out and dried. This steep is also repeated 4 times.

4. Steeping for a night in the river is the next process; a slight rinsing without wringing, and drying in the air.

5. Bath made of a warm decoction (100° F.) of sumach and nut-galls, in which the goods remain during the night; they are then strongly wrung, and dried in the air.

6. Aluming with addition of potash and chalk; wringing; working it well through this bath, where it is left during the night.

7. Draining, and strong rinsing the following day; piling up in a water cistern.

8. Rinsing repeated next day, and steeping in water to remove any excess of alum from the fibres; the goods continue in the water till they are taken to the dyeing-bath.

9. The maddering is made with the addition of blood, sumach, and nut-galls; the bath is brought to the boil in 1 hour and 3/4, and kept boiling for half an hour.

10. The yarn is rinsed, dried, boiled from 24 to 36 hours in a covered copper, with an oily alkaline liquid; then rinsed twice, laid for two days in clear water, and dried.

11. Finally, the greatest brightness is obtained by boiling for three or four hours in a soap bath, containing muriate of tin; after which the yarn is rinsed twice over, steeped in water, and dried.

Process of Haussmann.--He treats cotton twice or 4 times in a solution of aluminated potash, mixed with one thirty-eighth part of linseed oil. The solution is made by adding caustic potash to alum. He dries and rinses each time, and dries after the last operation. He then rinses and proceeds to the madder bath. For the rose colour, he takes one pound of madder for one pound of cotton; for carmine red, he takes from 2 to 3 pounds; and for the deepest red, no less than 4 pounds. It is said that the colour thus obtained surpasses Turkey red.

The French process, by Vitalis of Rouen.--First operation. Scouring with a soda lye, of 1° Baumé, to which there is usually added the remainder of the white preparation bath, which consists of oil and soda with water. It is then washed, wrung out, and dried.

In the second operation, he states that from 25 to 30 pounds of sheep’s dung are commonly used for 100 pounds of cotton yarn. The dung is first steeped for some days in a lye of soda, of 8° to 10° B. This is afterwards diluted with about 500 pints of a weaker ley, and at the same time bruised with the hand in a copper basin whose bottom is pierced with small holes. The liquor is then poured into a vat containing 5 or 6 pounds of fat oil (Gallipoli), and the whole are well mixed. The cotton is washed in this, and the hanks of yarn are then stretched on perches in the open air, and turned from time to time, so as to make it dry equably. After receiving thus a certain degree of desiccation, it is carried into the drying house, which is heated to 50° Reaumur (144° Fahrenheit), where it loses the remainder of its moisture, which would have prevented it from combining with the other mordants which it is afterwards to receive. What is left of the bath is called avances, and is added to the following bath. Two, or even three dung baths are given to the cotton, when it is wished to have very rich colours. When the cotton has received the dung baths, care must be taken not to leave it lying in heaps for any length of time, lest it should take fire; an accident which has occasionally happened.

The white bath is prepared by pouring 6 pounds of fat oil, into 50 pints of soda water, at 1° or sometimes less, according as, by a preliminary trial, the oil requires. This bath ought to be repeated two, three, or even a greater number of times, as more or less body is to be given to the colour.

To what remains of the white bath, and which is also styled avances, about 100 pints of soda lye of two or three degrees are added. Through this the cotton is passed as usual. Formerly it was the practice to give two, or three, or even four oils. Now, two are found to be sufficient.

The cotton is steeped for five or six hours in a tepid solution of soda, of 1° at most; it is set to drain, is then sprinkled with water, and at the end of an hour is washed, hank by hank, to purge it entirely from the oil. What remains of the water of degraissage, serves for the scouring or first operation.

For 100 pounds of cotton, from 20 to 25 pounds of galls in sorts must be taken, which are bruised and boiled in about 100 pints of water, till they crumble easily between the fingers. The galling may be done at two operations, dividing the above quantity of galls between them, which is thought to give a richer and more uniform colour.

The aluming of 100 pounds of cotton requires from twenty-five to thirty pounds of pure alum, that is, alum entirely free from ferruginous salts. The alum should be dissolved without boiling, in about 100 pints of river or rain water. When the alum is dissolved, there is to be poured in a solution of soda, made with the sixteenth part of the weight of the alum. A second portion of the alkaline solution must not be poured in till the effervescence caused by the first portion has entirely ceased,--and so in succession. The bath of saturated alum, being merely tepid, the cotton is passed through it, as in the gall bath, so as to impregnate it well, and it is dried with the precautions recommended above. The dyers who gall at two times, alum also twice, for like reasons.

For 25 pounds of cotton, 25 pints of blood are prescribed, and 400 pints of water. Whenever the bath begins to warm, 50 pounds of madder are diffused through the bath; though sometimes the maddering is given at two operations, by dividing the madder into two portions.

The brightening bath is prepared always for 100 pounds of cotton, with from four to five pounds of rich oil, six pounds of Marseilles white soap, and 600 litres of soda water of 2° B.

The rosing is given with solution of tin, mixed with soap water.

The Turkey-red dye of Messrs. Monteith and Co., of Glasgow, is celebrated all over the world, and merits a brief description here.

The calico is taken as it comes from the loom without bleaching, for the natural colour of the cotton wool harmonizes well with the dye about to be given; it is subjected to a fermentative steep for 24 hours, like that preliminary to bleaching, after which it is washed at the dash wheel. It is then boiled in a lye, containing about 1 pound of soda crystals for 12 pounds of cloth. The oiling process now begins. A bath is made with 10 gallons of Gallipoli oil, 15 gallon measures of sheep’s dung not indurated; 40 gallons of solution of soda crystals, of 1·06 specific gravity; 10 gallons of solution of pearl-ash of spec. grav. 1·04; and 140 gallons of water; constituting a milk-white, soapy solution of about spec. grav. 1·022. This liquor is put into a large cylindrical vat, and constantly agitated by the rotation of wooden vanes, which are best constructed on the plan of the mashing apparatus of a brewery, but far slighter. This saponaceous compound is let off as wanted by a stopcock into the trough of a padding machine, in order to imbue every fibre of the cloth in its passage. This impregnation is still more fully ensured by laying the padded cloth aside in wooden troughs during 16 or 18 days. The sheep’s dung has been of late years disused by many Turkey-red dyers both in England and France, but it is found to be advantageous in producing the very superior colour of the Glasgow establishment. It is supposed, also, to promote the subsequent bleaching during the exposure on the green; which is the next process in favourable weather, but in bad weather the goods are dried over a hot-flue.

The cloth is padded again with the saponaceous liquor; and again spread on the grass, or dried hard in the stove. This alternation is repeated a third time, and occasionally, even a fourth.

The cloth by this time is varnished as it were with oil, and must be cleansed in a certain degree by being passed through a weak solution of pearl-ash, at the temperature of about 122° F. It is then squeezed by the rollers and dried.

A second system of oiling now commences, with the following liquor:--10 gallons of Gallipoli oil; 30 gallons of soda crystals lye, of sp. grav. 1·06; and 10 gallons of caustic potash lye, of specific gravity 1·04, thoroughly diffused through 170 gallons of water. With this saponaceous liquor the cloth is padded as before, and then passed between squeezing-rollers, which return the superfluous liquor into the padding-trough. The cloth may be now laid on the grass if convenient; but at any rate it must be hard dried in the stove.

These saponifying, grassing, and drying processes, are repeated three times; whereby the cloth becomes once more very oleaginous, and must be cleansed again by steeping in a compound lye of soda crystals and pearl-ash of the spec. grav. 1·012, at the temperature of 122°. The cloth is taken out, squeezed between rollers to save the liquor, and washed. A considerable portion of the mingled alkalis disappear in this operation, as if they entered into combination with the oil in the interior of the cotton filaments. The cloth is now hard dried.

Galling is the next great step in the Turkey-red preparation; and for its success all the oil should have been perfectly saponified.

From 18 to 20 pounds of Aleppo galls (for each 100 libs of cloth) are to be bruised and boiled for 3 or 4 hours, in 25 gallons of water, till 5 gallons be evaporated; and the decoction is to be then passed through a searce. Two pounds of sumach may be substituted for every pound of galls. The goods must be well padded with this decoction, kept at 90° F., passed through squeezing-rollers, and dried. They are then passed through a solution of alum of the sp. gr. 1·04, to which a certain portion of chalk is added to saturate the acid excess of that supersalt; and in this cretaceous mixture, heated to 110°, the cloth is winced and steeped for 12 hours. It is then passed between squeezing-rollers, and dried in the stove.

The maddering comes next.

From two to three pounds of madder, ground to powder in a proper mill, are taken for every pound of cloth. The cloth, as usual in maddering, is entered into the cold bath, and winced by the automatic reel during one hour that the bath takes to boil, and during an ebullition of two hours afterwards. One gallon of bullock’s blood is added to the cold bath for every 25 pounds of cloth; being the quantity operated upon in one bath. The utility of the blood in improving the colour has been ascribed to its colouring particles; but it is more probably owing to its albuminous matter combining with the margarates of soda and potash condensed in the fibres.

As madder contains a dingy brown colouring matter associated with the fine red, the goods must be subjected to a clearing process to remove the former tinge, which is more fugitive than the latter. Every hundred pounds of cloth are therefore boiled during 12 hours at least, with water containing 5 pounds of soda crystals, 8 pounds of soap, and 16 gallons of the residual pearl-ash and soda-lye of the last cleansing operation. By this powerful means the dun matter is well nigh removed; but it is completely so by a second boil, at a heat of 250° F., in a tight globular copper, along with 5 pounds of soap, and 1 pound of muriate of tin crystals, dissolved in a sufficient body of water for 100 pounds of cloth. The muriate of tin serves to raise the madder red to a scarlet hue. A margarate of tin is probably fixed upon the cloth in this operation.

When the weather permits, the goods should be now laid out for a few days on the grass. Some manufacturers give them a final brightening with a weak bath of a chloride of lime; but it is apt to impoverish the colour.

According to the latest improvements of the French dyers, each of the four processes of oiling, mordanting, dyeing, and brightening differs, in some respects, from the above.

1. Their first step is boiling the cloth for four hours, in water containing one pound of soap for every four pieces. Their saponaceous bath of a creamy aspect is used at a temperature of 75° F.; and it is applied by the padding machine 6 times, with the grassing and drying alternations. In winter, when the goods cannot be exposed on the grass, no less than 12 alternations of the saponaceous or white bath are employed, and 8 in spring. They consider the action of the sun-beam to aid greatly in brightening this dye; but at Midsummer, if it be continued more than 4 hours, the scarlet colour produced begins to be impaired.

They conceive that the oiling operation impregnates the fibres with super-margarate of potash or soda, insoluble salts which attract and condense the alumina, and the red colouring particles of the madder, so firmly that they can resist the clearing boil.

2. Their second step, the mordanting, consists first in padding the pieces through a decoction of galls mixed with a solution of an equal weight of alum; and after drying in the hot-flue, &c., again padding them in a solution of an acetate of alumina, made by decomposing a solution of 16 libs. of alum with 16 libs of acetate of lead, for 6 pieces of cloth, each 32 aunes long.

3. The maddering is given at two successive operations; with 4 pounds of Avignon madder per piece at each time.

4. The brightening is performed by a 12 hours’ boil in water with soda crystals, soap, and salt of tin; and the rosing by a 10 hours’ boil with soap and salt of tin. Occasionally, the goods are passed through a weak solution of chloride of potash. When the red has too much of a crimson cast, the pieces are exposed for two days on the grass, which gives them a bright scarlet tint.

Process of M. Werdet to dye broad cloth and wool by madder:--

“Preparation for 24 pounds of scoured wool:

“Take 4-1/4 pounds of cream of tartar, 4-1/4 pounds of pure alum; boil the wool gently for 2 hours, transfer it into a cool place, and wash it next day in clear water.

“Dyeing.--12 pounds of Avignon madder, infused half an hour at 30° R. (100° F.) Put into the bath 1 pound of muriate of tin, let the colour rose for three quarters of an hour at the same heat, and drain or squeeze the madder through canvas. The whole of the red dye will remain upon the filter, but the water which has passed through will be as deep a yellow as a weld bath. The boiler with the dye must now be filled up with clear river water, and heated to 100° F. Two ounces of the solution of the tartar and alum must be poured into it, and the wool must be turned over in it for an hour and a half, while the heat is gradually raised to the boiling point. The wool is then removed and washed. It must be rosed the following day.

“Rosing.--Dissolve in hot water 1 pound of white Marseilles soap; let the bath cool, and pass the wool through it till it has acquired the desired shade; 15 or 20 minutes are sufficient. On coming out of this bath it should be washed.

“Solution of deuto-muriate of tin:--

“2 ounces of pure muriatic acid; 4 drachms of pure nitric acid; 1 ounce of distilled water. Dissolve in it, by small portions at a time, 2 drachms of grain tin, in a large bottle of white glass, shutting it after putting in the tin. This solution may be preserved for years, without losing its virtue.”

I have inserted this process, as recently recommended by the French minister of commerce, and published by M. Pouillet in vol. i. of his Portefeuille Industriel, to show what official importance is sometimes given by our neighbours to the most frivolous things.

Madders imported for home consumption. Gross amount of Duty paid in 1836. 1837. 1836. 1837. Cwts. 106,172 | cwts. 79,228 | _£_10,810 | _£_8,081

MADREPORES, are calcareous incrustations produced by polypi contained in cells of greater or less depth, placed at the surface of calcareous ramifications, which are fixed at their base, and perforated with a great many pores. The mode of the increase, reproduction and death of these animals is still unknown to naturalists. Living madrepores are now-a-days to be observed only in the South American, the Indian, and the Red seas; but although their polypi are not found in our climate at present, there can be no doubt of their having existed in these northern latitudes in former times, since fossil madrepores occur in both the older and newer secondary strata of Europe.

MAGISTERY, is an old chemical term to designate white pulverulent substances, spontaneously precipitated in making certain metallic solutions; as magistery of bismuth.

MAGISTRAL, in the language of the Spanish smelters of Mexico and South America, is the roasted and pulverized copper pyrites, which is added to the ground ores of silver in their patio, or amalgamation magma, for the purpose of decomposing the horn silver present. See SILVER, for an account of this curious process of reduction.

MAGMA, is the generic name of any crude mixture of mineral or organic matters, in a thin pasty state.

MAGNANIER, is the name given in the southern departments of France to the proprietor of a nursery in which silk-worms are reared upon the great scale, or to the manager of the establishment. The word is derived from magnans, which signifies silkworms in the language of the country people. See SILK.

MAGNESIA (Eng. and Fr.; Bittererde, Talkerde, Germ.), is one of the primitive earths, first proved by Sir H. Davy to be the oxide of a metal, which he called magnesium. It is a fine, light, white powder, without taste or smell, which requires 5150 parts of cold water, and no less than 36,000 parts of boiling water, for its solution. Its specific gravity is 2·3. It is fusible only by the heat of the hydroxygen blowpipe. A natural hydrate is said to exist which contains 30 per cent. of water. Magnesia changes the purple infusion of red cabbage to a bright green. It attracts carbonic acid from the air, but much more slowly than quicklime. It consists of 61·21 parts of metallic basis, and 38·79 of oxygen; and has, therefore, 20 for its prime equivalent upon the hydrogen scale. Its only employment in the arts is for the purification of fine oil, in the preparation of varnish.

Magnesia may be obtained by precipitation with potash or soda, from its sulphate, commonly called Epsom salt; but it is usually procured by calcining the artificial or natural carbonate. The former is, properly speaking, a subcarbonate, consisting of 44·69 magnesia, 35·86 carbonic acid, and 19·45 water. It is prepared by adding to the solution of the sulphate, or the muriate (the bittern of sea-salt evaporation works), a solution of carbonate of soda, or of carbonate of ammonia distilled from bones in iron cylinders. The sulphate of magnesia is generally made by acting upon magnesian limestone with somewhat dilute sulphuric acid. The sulphate of lime precipitates, while the sulphate of magnesia remains in solution, and may be made to crystallize in quadrangular prisms, by suitable evaporation and slow cooling. Where muriatic acid may be had in profusion for the trouble of collecting it, as in the soda works in which sea salt is decomposed by sulphuric acid, the magnesian limestone should be first acted upon with as much of the former acid as will dissolve out the lime, and then, the residuum being treated with the latter acid, will afford a sulphate at the cheapest possible rate; from which magnesia and all its other preparations may be readily made. Or, if the equivalent quantity of calcined magnesian limestone be boiled for some time in bittern, the lime of the former will displace the magnesia from the muriatic acid of the latter. This is the most economical process for manufacturing magnesia. The subcarbonate, or magnesia alba of the apothecary, has been proposed by Mr. E. Davy to be added by the baker to damaged flour, to counteract its acescency.

MAGNESIAN LIMESTONE (Dolomie, Fr.; Bittertalk, Talkspath, Germ.), is a mineral which crystallizes in the rhombohedral system. Spec. grav. 2·86; scratches calc-spar; does not fall spontaneously into powder, when calcined, as common limestone does. It consists of 1 prime equivalent of carbonate of lime = 50, associated with 1 of carbonate of magnesia = 42.

Massive magnesian limestone, is yellowish-brown, cream-yellow, and yellowish-gray; brittle. It dissolves slowly and with feeble effervescence in dilute muriatic acid; whence it is called Calcaire lent dolomie by the French mineralogists. Specific gravity 2·6 to 2·7.

Near Sunderland, it is found in flexible slabs. The principal range of hills composing this geological formation in England, extends from Sunderland on the northeast coast to Nottingham, and its beds are described as being about 300 feet thick on the east of the coal field in Derbyshire, which is near its southern extremity. On the western side of the Cumberland mountains magnesian limestone overlies the coal measures near Whitehaven. The stratification of this rock is very distinct, the individual courses of stone not exceeding in general the thickness of a common brick.

The lime resulting from the calcination of magnesian limestone appears to have an injurious action on vegetation, unless applied in quantities considerably less than common lime, when it is found to fertilize the soil. After two years, its hurtful influence on the ground seems to become exhausted, even when used in undue quantity. Great quantities of it are annually brought from Sunderland to Scotland by the Fifeshire farmers, and employed beneficially by them, as a manure, in preference to other kinds of lime. It has been unfairly denounced by Mr. Tennent and Sir H. Davy, as a sterilizer.

This rock is used in many places for building; indeed our most splendid monument of Gothic architecture, York Minster, is constructed of magnesian limestone.

MAGNESIA, NATIVE (Brucite; Guhr magnésien, Fr.; Wassertalk, Germ.), is a white, lamellar, pearly-looking mineral, soft to the touch. Spec. grav. 2·336; tender; scratched by calc-spar; affording water by calcination; leaving a white substance which browns turmeric paper; and, by calcination with nitrate of cobalt, becoming of a lilac hue. It consists of 69·75 magnesia, and 30·25 water. It occurs in veins in the serpentine at Hoboken, in New Jersey, as also at Swinaness, in the island of Unst, Shetland.

MAGNESITE, Giobertite; native carbonate of magnesia, occurs in white, hard, stony masses, in the presidency of Madras, and in a few other localities. It dissolves very slowly in muriatic acid, and gives out carbonic acid in the proportion of 22 parts by weight to 42 of the mineral, according to my experiments, and is therefore an atomic carbonate. It forms an excellent and beautiful mortar cement for terraces; a purpose to which it has been beneficially applied in India by Dr. Macleod.

MAGNET, NATIVE, is a mineral consisting of the protoxide and peroxide of iron combined in equivalent proportions. See IRON.

MAHALEB. The fruit of this shrub affords a violet dye, as well as a fermented liquor like Kirschwasser. It is a species of cherry cultivated in our gardens.

MALACHITE, or mountain green, is native carbonate of copper of a beautiful green colour, with variegated radiations and zones; spec. grav. 3·5; it scratches calc-spar, but not fluor; by calcination it affords water and turns black. Its solution in the acids, deposits copper upon a plate of iron plunged into it. It consists of carbonic acid 18·5; deutoxide of copper 72·2; water 9·3.

MALATES, are saline compounds of the bases, with

MALIC ACID. (Acide malique, Fr.; Aepfelsäure, Germ.) This acid exists in the juices of many fruits and plants, alone, or associated with the citric, tartaric, and oxalic acids; and occasionally combined with potash or lime. Unripe apples, sloes, barberries, the berries of the mountain ash, elder berries, currants, gooseberries, strawberries, raspberries, bilberries, brambleberries, whortleberries, cherries, ananas, afford malic acid; the house-leek and purslane contain the malate of lime.

The acid may be obtained most conveniently from the juice of the berries of the mountain ash, or barberries. This must be clarified, by mixing with white of egg, and heating the mixture to ebullition; then filtering, digesting the clear liquor with carbonate of lead, till it becomes neutral; and evaporating the saline solution, till crystals, of malate of lead be obtained. These are to be washed with cold water, and purified by re-crystallization. On dissolving the white salt in water, and passing a stream of sulphuretted hydrogen through the solution, the lead will be all separated in the form of a sulphuret, and the liquor, after filtration and evaporation, will yield yellow granular crystals, or cauliflower concretions, of malic acid, which may be blanched by re-dissolution and digestion with bone-black, and re-crystallization.

Malic acid has no smell, but a very sour taste, deliquesces by absorption of moisture from the air, is soluble in alcohol, fuses at 150° Fahr., is decomposed at a heat of 348°, and affords by distillation a peculiar acid, the pyromalic. It consists in 100 parts, of 41·47 carbon; 3·51 hydrogen; and 55·02 oxygen; having nearly the same composition as citric acid. A crude malic acid might be economically extracted from the fruit of the mountain ash, applicable to many purposes; but it has not hitherto been manufactured upon the great scale.

MALLEABILITY, is the property belonging to certain metals, of being extended under the hammer. A table of malleability is given in the article DUCTILITY.

MALT; (Eng. and Fr.; Malz, Germ.) is barley-corn, which has been subjected to an artificial process of germination. See BEER.

Table of the Quantity of Malt consumed by the undermentioned Brewers of London and Vicinity, from October 10th, 1836, to October 10th, 1837.

+--------------------------------+-------+ | Brewers. | Qrs. | +--------------------------------+-------+ |Barclay and Co. | 100005| |Hanbury and Co. | 82798| |Whitbread and Co. | 47012| |Reid and Co. | 43945| |Combe and Co. | 40366| |Hoare and Co. | 32347| |Calvert and Co. | 32335| |Meux and Co. | 30575| |Elliot and Co. | 24154| |Taylor and Co. | 23556| |Charrington and Co. | 18842| |Thorne and Son | 16404| |Gardner | 15256| |Ramsbottom and Co. | 15227| |J. & C. Goding (11 months) | 14023| |Bricheno | 9863| |Courage and Co. | 9284| |Wood and Co. | 7834| |Goding, Thos. | 7095| |Hazard | 6674| |Mann, Jas. | 6588| |Harris, Thos. | 6042| |More | 6025| |M’Leod, B. | 4960| |Farren and Till | 4783| |Manners and Co. | 4552| |Hale, George. | 4547| |Halford and Topham | 3786| |Stains and Fox | 5783| |Lamont and Co. | 3600| |Laxton | 3583| |Richmond | 3174| |Maynard | 3133| |M’Leod and Thompson | 2834| |Tubb | 2826| |Johnson and Wyatt | 2809| |Duggan and Co. | 2665| |Hodgson | 2400| |Sherborn and Co. | 2347| |Griffith | 2221| |Cox, John | 2151| |Masterman | 1914| |Hill and Rice | 1853| |Gray and Dacre | 1760| |Plimmer | 1747| |Hayward | 1737| |Verey, W. and C. | 1573| |Williamson and Co. | 1566| |Honeyball | 1512| |Satchell and Son | 1441| |Clarke, C. | 1330| |Colyer | 1299| |Filmer and Wall | 1298| |Nicholls and Co. | 1240| |Hagan | 1143| |Hume | 1126| |Buckley and Co. | 1025| |Verey, J. | 1017| |Collins, J. | 966| |Jones | 956| |Ufford and Oldershaw | 953| |Blogg, B. | 943| |Ing | 900| |Keep | 886| |Soulby | 861| |Clarke, R. | 834| |Jenner | 833| |Manvell | 824| |M’Leods | 820| |Braithwaite | 799| |Addison | 768| |Turner | 766| |Holt | 756| |Church | 742| |Clarke, S. | 741| |Mann, Joel | 733| |Turner | 712| |Mantell | 693| |Lock | 651| |Hood | 649| |Pink, A. | 636| |Collins | 598| |Wright | 588| |West | 565| |Abbott | 560| |Hett (6 months) | 552| |Wells | 520| |Higgs | 475| |Harris, Robt. | 470| |Woodward | 462| |Wicks | 441| |Bell | 440| |Thompson | 406| |Mattam | 400| |M’Intosh | 397| |Thurlby | 392| |Griffiths | 391| |Kay | 360| |Tidman | 332| |Lindsay | 326| |Cooper | 315| |West | 306| |Carpenter | 299| |Green | 292| |Chapman | 286| |Brace | 266| |Clark | 248| |Allen | 245| |Powditch | 238| |Garnett | 232| |Hill | 222| |Olley | 214| |Ward | 206| |Bye | 201| |Newton | 175| |Chadwick | 169| |Prosser | 166| |Smith | 164| |Edwards | 156| |Pugh | 155| |Hainstock | 155| |Lloyd | 154| |Reynolds | 151| |Latham | 142| |Meaton | 140| |Brewer | 135| |Stirling | 133| |Ambler | 130| |Potter | 122| |Champion | 121| |Miller | 115| |Edwards | 108| |Easton | 105| |Griffiths | 105| |Hopkins | 91| |Hudson | 90| |Thorpe | 89| |Burt | 88| |Bowden | 88| |Batt | 84| |Phillips | 83| |Jewit | 82| |Tyler | 76| |Whittaker | 75| |Begbie | 75| |Carter | 75| |Priddle | 74| |Coomber | 73| |Stallwood | 71| |Jones | 71| |Rose | 67| |Norris | 67| |Remnant | 62| |Kearney | 62| |Smith | 62| |Woodroffe | 60| |Knight | 60| |Graves | 54| |Sheppard | 52| |Field | 51| |Bradfield | 51| |Webb | 50| |Chapman | 48| |Price | 45| |Godfrey | 45| |Hobbs | 32| |Denman | 31| +--------------------------------+-------+ | Qrs. | |Quantity used 1836, 754,313| |Quantity used 1837, 714,488| | -------| | Decrease 1837, 39,825| | -------| | JOHN SLATER, Cask Inspector. | |Hop-Duty, 1837. (Old) _£_178,578. | |3_s._ 0-1/2_d._ | +----------------------------------------+

Table of the Quantity of Malt from Barley, which paid Duty in

+------+----------+---------+---------+ |Years.| England. |Scotland.| Ireland.| +------+----------+---------+---------+ | | Bushels. | Bushels.| Bushels.| |1834. |34,949,646|3,580,758|1,776,883| |1835. |36,078,855|3,604,816|1,825,300| |1836. |37,196,998|4,168,854|1,872,104| | | | Amount of Duties paid: | | | £ | £ | £ | |1834. | 4,449,745| 462,514| 229,514| |1835. | 4,660,185| 465,622| 235,767| |1836. | 4,804,612| 538,477| 241,813| +------+----------+---------+---------+

MALT KILN; (Darre, Germ.) The improved malt kiln of Pistorius is represented fig. 653. in a top view; fig. 654. in a longitudinal view and section; and fig. 655., in transverse section. a a, are two quadrangular smoke flues, constructed of fire-tiles, or fire-stones, and covered with iron plates, over which a pent-house roof is laid; the whole bound by the cross pieces b (figs. 654, 655.) These flues are built above a grating c c, which commences at c´; in front of c´ there is a bridge of bricks. Instead of such a brick flue covered with plates, iron pipes may be used, covered with semi-cylindrical tiles, to prevent the malt that may happen to fall from being burned. d d, are the breast walls of the kiln, 3 feet high, furnished with two apertures shut with iron doors, through which the malt that drops down may be removed from time to time. e is a beam of wood lying on the breast wall, against which the hurdles are laid down slantingly towards the back wall of the kiln; f f, are two vertical flues left in the substance of the walls, through which the hot air, discharged by open pipes laid in a subjacent furnace, rises into the space between the pent-house roof and the iron plates, and is thence allowed to issue through apertures in the sides. g is the discharge flue in the back wall of the kiln for the air now saturated with moisture; h is the smoke-pipe, from which the smoke passes into the anterior flue a, provided with a slide-plate, for modifying the draught; the smoke thence flows off through a flue fitted also with a damper-plate into the chimney i. k is the smoke-pipe of a subsidiary fire, in case no smoke should pass through h. The iron pipes are 11 inches in diameter, the air-flue f, 5 inches, and the smoke-pipe h, 10 inches square; the brick flues 10 inches wide, and the usual height of bricks.

MALTHA; Bitume Glutineux, or mineral pitch. It is a soft glutinous substance, with the smell of pitch. It dissolves in alcohol, but leaves a bituminous residuum; as also in naphtha, and oil of turpentine. It seems to be inspissated petroleum.

MANGANESE, (Eng. and Fr.; Mangan, Braunsteinmetal, Germ.) is a grayish-white metal, of a fine-grained fracture, very hard, very brittle, with considerable lustre, of spec. grav. 8·013, and requiring for fusion the extreme heat of 160° Wedgewood. It should be kept in closely stoppered bottles, under naphtha, like potassium, because with contact of air it speedily gets oxidized, and falls into powder. It decomposes water slowly at common temperatures, and rapidly at a red heat. Pure oxide of manganese can be reduced to the metallic state only in small quantities, by mixing it with lamp black and oil into a dough, and exposing the mixture to the intense heat of a smith’s forge, in a luted crucible; which must be shaken occasionally to favour the agglomeration of the particles into a button. Thus procured, it contains, however, a little carbon.

Manganese is susceptible of five degrees of oxigenation:--

1. The protoxide may be obtained from a solution of the sulphate by precipitation with carbonate of potash, and expelling the carbonic acid from the washed and dried carbonate, by calcination in a close vessel filled with hydrogen gas, taking care that no air have access during the cooling. It is a pale green powder, which slowly attracts oxygen from the air, and becomes brown; on which account it should be kept in glass tubes, containing hydrogen, and hermetically sealed. It consists of 77·57 metal and 22·43 oxygen. It forms with 24 per cent. of water a white hydrate; and with acids, saline compounds; which are white, pink, or amethyst coloured. They have a bitter, acerb taste, and afford with hydrogenated sulphuret of ammonia, a flesh-red precipitate, but with caustic alkalis, one which soon turns brown-red, and eventually black.

2. The deutoxide of manganese exists native in the mineral called Braunite; but it may be procured either by calcining, at a red heat, the proto-nitrate, or by spontaneous oxidizement of the protoxide in the air. It is black; when finely pulverized, dark brown, and is convertible, on being heated in acids, into protoxide, with disengagement of oxygen gas. It consists of 69·75 metal, and 30·25 oxygen. It forms with 10 per cent. of water, a liver-brown hydrate, which occurs native under the name of Manganite. It dissolves readily in tartaric and citric acids, but in few others. This oxide constitutes a bronze ground in calico-printing.

3. Peroxide of manganese; Braunstein, occurs abundantly in nature. It gives out oxygen freely when heated, and becomes an oxidulated deutoxide. It consists of 63·36 metal, and 36·64 oxygen.

4. Manganesic acid, forms green-coloured salts, but has not hitherto been insulated from the bases. It consists of 53·55 metal, and 46·45 oxygen.

5. Hypermanganesic acid, consists of 49·70 metal, and 50·30 oxygen.

Ores of manganese.--There are two principal ores of this metal which occur in great masses; the peroxide and the hydrated oxide; the first of which is frequently found in primitive formations.

1. Metalloide oxide of manganese; pyrolusite, or gray manganese ore; has a metallic lustre, a steel gray colour, and affords a black powder. Spec. grav. 4·85. Scratches calc-spar. It effervesces briskly with borax at the blow-pipe, in consequence of the disengagement of oxygen gas. This is the most common ore of manganese, and a very valuable one, being the substance mostly employed in the manufacture of chloride of lime and of flint-glass. It is the peroxide. Great quantities are found near Tavistock, in Devonshire, and Launceston, in Cornwall.

2. Braunite, is a dark brown substance, of a glassy metallic lustre, affording a brown powder. Spec. grav. 4·8. It scratches felspar; but is scratched by quartz. Infusible at the blow-pipe, and effervesces but slightly when fused with glass of borax. It is the deutoxide. It gives out at a red heat only 3 per cent. of oxygen.

3. Manganite, or hydroxide of manganese; is brownish-black or iron-black, powder brown, with somewhat of a metallic lustre. Spec. grav. 4·3. Scratches fluor spar; affords water by calcination in a glass tube; infusible at the blow-pipe; and effervesces slightly when fused with glass of borax. It consists of about 90 of deutoxide, and 10 of water.

4. Haussmanite, black braunstein; is brownish-black, affords a reddish-brown powder. Spec. grav. 4·7; scratches fluor spar; infusible at the blow-pipe; does not effervesce when fused with borax. It is a deutoxide. This is a rare mineral, and of no value to the arts.

5. Barytic oxide of manganese; fibrous wad. It is a combination of deutoxide and peroxide, with some baryta.

6. Manganese blende, or sulphuret of manganese; has a metallic aspect; is black, or dark steel gray; spec. grav. 3·95; has no cleavage; cannot be cut; infusible, but affords after being roasted distinct evidence of manganese, by giving a violet tinge to soda at the blow-pipe. Soluble in nitric acid; solution yields a white precipitate with the ferro-cyanide of potassium. It consists of sulphur 53·65; manganese 66·35.

7. Carbonate of manganese; dialogite. Spec. grav. 3·4; affords a green frit by fusion with carbonate of soda; is soluble with some effervescence in nitric acid; solution when freed from iron by succinate of ammonia, gives a white precipitate, with ferrocyanide of potassium. It consists of 28 carbonic acid, 56 protoxide of manganese, 5·4 of lime, 4·5 protoxide of iron, and 0·8 magnesia.

8. Hydrosilicate of manganese; is a black metallic looking substance, which yields a yellowish-brown powder, and water by calcination; is acted upon by muriatic acid, but affords no chlorine. It consists of silica 25; protoxide of manganese 60; water 13.

9. Ferriferous phosphate of manganese, is brown or black. Spec. grav. 3·6; scratches fluor; affords by calcination a very little of an acid water which corrodes glass; very fusible at the blow-pipe into a black metalloid magnetic bead; is acted upon by nitric acid: solution lets fall a blue precipitate with ferrocyanide of potassium; which tested by soda is shown to be manganese. It consists of phosphoric acid 32·78; protoxide of iron 31·90; protoxide of manganese 32·60; phosphate of lime 3·2. Another phosphate called hureaulite, contains 38 of phosphoric acid; 11·10 of protoxide of iron; 32·85 of protoxide of manganese, and 18 of water.

Black wad, is the old English name of the hydrated peroxide of manganese. It occurs in various imitative shapes, in froth-like coatings upon other minerals, as also massive. Some varieties possess imperfect metallic lustre. The external colour is brown of various shades, and similar in the streak, only shining. It is opaque, very sectile, soils and writes. Its specific gravity is about 3·7. Mixed with linseed oil into a dough, black wad forms a mass that spontaneously inflames. A variety from the Hartz, analyzed by Klaproth, afforded peroxide of manganese 68; oxide of iron 6·5; water 17·5; carbon 1; barytes and silica 9. The localities of black wad are particularly Cornwall and Devonshire, the Hartz, and Piedmont. I have analyzed many varieties of the black wad sold to the manufacturers of bleaching salt, and flint glass, and have found few of them so rich in peroxide of manganese as the above. Very generally they contained no less than 25 per cent. of oxide of iron, 8 or 9 of silica, about 7 of water, and the remainder amounting to only 60 per cent. of the peroxide.

M. Gay Lussac has proposed to determine the commercial value of manganese ore, by the quantity of chlorine which it affords when treated with liquid muriatic acid. He places the manganese powder in a small retort or matras, pours over it the acid, and the chlorine being disengaged with the aid of a gentle heat, is transmitted into a vessel containing milk of lime or potash water. This liquor is thereafter poured into a dilute solution of sulphate of indigo; and the quantity of chlorine is inferred from the quantity of the blue solution which is decoloured. I pass the chlorine into test solution of indigo.

The manufacturer of flint glass uses a small proportion of the black manganese ore, to correct the green tinge which his glass is apt to derive from the iron present in the sand he employs. To him it is of great consequence to get a native manganese containing as little iron oxide as possible; since in fact the colour or limpidity of his product will depend altogether upon that circumstance.

Sulphate of manganese has been of late years introduced into calico printing, to give a chocolate or bronze impression. It is easily formed by heating the black oxide, mixed with a little ground coal, with sulphuric acid. See CALICO PRINTING.

The peroxide of manganese is used also in the formation of glass pastes, and in making the black enamel of pottery. See OXALIC ACID.

MANGLE. (Calandre, Fr.; Mangel, Germ.) This is a well known machine for smoothing table cloths, table napkins, as well as linen and cotton furniture. As usually made, it consists of an oblong rectangular wooden chest, filled with stones, which load it to the degree of pressure that it should exercise upon the two cylinders on which it rests, and which, by rolling backwards and forwards over the linen spread upon a polished table underneath, render it smooth and level. The moving wheel, being furnished with teeth upon both surfaces of its periphery, and having a notch cut out at one part, allows a pinion, uniformly driven in one direction, to act alternately upon its outside and inside, so as to cause the reciprocating motion of the chest. This elegant and much admired English invention, called the mangle-wheel, has been introduced with great advantage into the machinery of the textile manufactures.

Mr. Warcup, of Dartford, obtained a patent several years ago for a mangle, in which the linen, being rolled round a cylinder revolving in stationary bearings, is pressed downwards by heavy weights hung upon its axes, against a curved bed, made to slide to and fro, or traverse from right to left, and left to right, alternately.

Mr. Hubie, of York, patented in June, 1832, another form of mangle, consisting of three rollers, placed one above another in a vertical frame, the axle of the upper roller being pressed downwards by a powerful spring. The articles intended to be smoothed are introduced into the machine by passing them under the middle roller, which is made to revolve by means of a fly wheel; the pinion upon whose axis works in a large toothed wheel fixed to the shaft of the same roller. The linen, &c. is lapped as usual in protecting cloths. This machine is merely a small CALENDER.

MANIOC, is the Indian name of the nutritious matter of the shrub jatropha manihot, from which cassava and tapioca are made in the West Indies.

MANNA, is the concrete saccharine juice of the Fraxinus ornus, a tree much cultivated in Sicily and Calabria. It is now little used, and that only in medicine.

MARBLE. This title embraces such of the primitive, transition, and purer compact limestones of secondary formation, as may be quarried in solid blocks without fissures, and are susceptible of a fine polished surface. The finer the white, or more beautifully variegated the colours of the stone, the more valuable, ceteris paribus, is the marble. Its general characters are the following:--

Marble effervesces with acids; affords quicklime by calcination; has a conchoidal scaly fracture; is translucent only on the very edges; is easily scratched by the knife; has a spec. grav. of 2·7; admits of being sawn into slabs; and receives a brilliant polish. These qualities occur united in only three principal varieties of limestone; in the saccharoid limestone, so called from its fine granular texture resembling that of loaf sugar, and which constitutes modern statuary marble, like that of Carrara; 2. in the foliated limestone, consisting of a multitude of small facets formed of little plates applied to one another in every possible direction, constituting the antique statuary marble, like that of Paros; 3. in many of the transition and carboniferous, or encrinitic limestones, subordinate to the coal formation.

The saccharoid and lamellar, or statuary marbles, belong entirely to primitive and transition districts. The greater part of the close-grained coloured marbles belong also to the same geological localities; and become so rare in the secondary limestone formations, that immense tracts of these occur without a single bed sufficiently entire and compact to constitute a workable marble. The limestone lying between the calcareo-siliceous sands and gritstone of the under oolite, and which is called Forest marble in England, being susceptible of a tolerable polish, and variegated with imbedded shells, has sometimes been worked into ornamental slabs in Oxfordshire, where it occurs in the neighbourhood of Whichwood forest; but this case can hardly be considered as an exception to the general rule. To constitute a profitable marble-quarry, there must be a large extent of homogeneous limestone, and a facility of transporting the blocks after they are dug. On examining these natural advantages of the beds of Carrara marble, we may readily understand how the statuary marbles discovered in the Pyrenees, Savoy, Corsica, &c. have never been able to come into competition with it in the market. In fact, the two sides of the valley of Carrara may be regarded as mountains of statuary marble of the finest quality.

Gypseous alabaster may be readily distinguished from marbles, because it does not effervesce with acids, and is soft enough to be scratched by the nail; stalagmitic alabaster is somewhat harder than marble, translucent, and variegated with regular stripes or undulations.

Some granular marbles are flexible in thin slabs, or, at least, become so by being dried at the fire; which shews, as Dolomieu suspected, that this property arises from a diminution of the attractive force among the particles, by the loss of the moisture.

The various tints of ornamental marbles generally proceed from oxides of iron; but the blue and green tints are sometimes caused by minute particles of hornblende, as in the slate-blue variety called Turchino, and in some green marbles of Germany. The black marbles are coloured by charcoal, mixed occasionally with sulphur and bitumen; when they constitute stinkstone.

Brard divides marbles, according to their localities, into classes, each of which contains eight subdivisions:--

1. Uni-coloured marbles; including only the white and the black.

2. Variegated marbles; those with irregular spots or veins.

3. Madreporic marbles, presenting animal remains in the shape of white or gray spots, with regularly disposed dots and stars in the centre.

4. Shell marbles; with only a few shells interspersed in the calcareous base.

5. Lumachella marbles, entirely composed of shells.

6. Cipolin marbles, containing veins of greenish talc.

7. Breccia marbles, formed of a number of angular fragments of different marbles, united by a common cement.

8. Puddingstone marbles; a conglomerate of rounded pieces.

Antique marbles.--The most remarkable of these are the following:--Parian marble, called lychnites by the ancients, because its quarries were worked by lamps; it has a yellowish-white colour; and a texture composed of fine shining scales, lying in all directions. The celebrated Arundelian tables at Oxford consist of Parian marble, as well as the Medicean Venus. Pentelic marble, from Mount Penteles, near Athens, resembles the Parian, but is somewhat denser and finer grained, with occasional greenish zones, produced by greenish talc, whence it is called by the Italians Cipolino statuario. The Parthenon, Propyleum, the Hippodrome, and other principal monuments of Athens, were of Pentelic marble; of which fine specimens may be seen among the Elgin collection, in the British Museum. Marmo Greco, or Greek white marble, is of a very lively snow white colour, rather harder than the preceding, and susceptible of a very fine polish. It was obtained from several islands of the Archipelago, as Scio, Samos, Lesbos, &c. Translucent white marble, Marmo statuario of the Italians, is very much like the Parian, only not so opaque. Columns and altars of this marble exist in Venice, and several towns of Lombardy; but the quarries are quite unknown. Flexible white marble, of which five or six tables are preserved in the house of Prince Borghese, at Rome. The White marble of Luni, on the coast of Tuscany, was preferred by the Greek sculptors to both the Parian and Pentelic. White marble of Carrara, between Specia and Lucca, is of a fine white colour, but often traversed by gray veins, so that it is difficult to procure moderately large pieces free from them. It is not so apt to turn yellow as the Parian marble. This quarry was worked by the ancients, having been opened in the time of Julius Cæsar. Many antique statues remain of this marble. Its two principal quarries at the present day are those of Pianello and Polvazzo. In the centre of its blocks very limpid rock-crystals are sometimes found, which are called Carrara diamonds. As the finest qualities are becoming excessively rare, it has risen in price to about 3 guineas the cubic foot. The White marble of Mount Hymettus, in Greece, was not of a very pure white, but inclined a little to gray. The statue of Meleager, in the French Museum, is of this marble.

Black antique marble, the Nero antico of the Italians. This is more intensely black than any of our modern marbles; it is extremely scarce, occurring only in sculptured pieces. The red antique marble, Egyptum of the ancients, and Rosso antico of the Italians, is a beautiful marble of a deep blood-red colour, interspersed with white veins and with very minute white dots, as if strewed over with grains of sand. There is in the Grimani palace at Venice, a colossal statue of Marcus Agrippa in rosso antico, which was formerly preserved in the Pantheon at Rome. Green antique marble, verde antico, is a kind of breccia, whose paste is a mixture of talc and limestone, while the dark green fragments consist of serpentine. Very beautiful specimens of it are preserved at Parma. The best quality has a grass-green paste, with black spots of noble serpentine, but is never mingled with red spots. Red spotted green antique marble, has a dark green ground marked with small red and black spots, with fragments of entrochi changed into white marble. It is known only in small tablets. Leek marble; a rare variety of that colour, of which there is a table in the Mint at Paris. Marmo verde pagliocco is of a yellowish green colour, and is found only in the ruins of ancient Rome. Cervelas marble of a deep red, with numerous gray and white veins, is said to be found in Africa, and highly esteemed in commerce. Yellow antique marble, giallo antico of the Italians; colour of the yolk of an egg, either uniform or marked with black or deep yellow rings. It is rare, but may be replaced by Sienna marble. Red and white antique marbles, found only among the ruins of ancient Rome. Grand antique, a breccia marble, containing shells, consists of large fragments of a black marble, traversed by veins or lines of a shining white. There are four columns of it in the Museum at Paris. Antique Cipolino marble. Cipolin is a name given to all such marbles as have greenish zones produced by green talc; their fracture is granular and shining, and displays here and there plates of talc. Purple antique breccia marble, is very variable in the colour and size of its spots. Antique African breccia, has a black ground, variegated with large fragments of a grayish-white, deep red, or purplish wine colour; and is one of the most beautiful marbles. Rose-coloured antique breccia marble is very scarce, occurring only in small tablets. There are various other kinds of ancient breccias, which it would be tedious to particularize.

Modern marbles.--1. British. Black marble is found at Ashford, Matlock, and Monsaldale in Derbyshire; black and white in the north part of Devonshire; the variegated marbles of Devonshire are generally reddish, brownish, and grayish, variously veined with white and yellow, or the colours are often intimately blended; the marbles from Torbay and Babbacombe, display a great variety in the mixture of their colours; the Plymouth marble is either ash-coloured with black veins, or blackish-gray and white, shaded with black veins; the cliffs near Marychurch exhibit marble quarries not only of great extent, but of superior beauty to any other in Devonshire, being either of a dove-coloured ground with reddish-purple and yellow veins, or of a black ground mottled with purplish globules. The green marble of Anglesea is not unlike the verde antico; its colours being greenish-black, leek-green, and sometimes dull purplish, irregularly blended with white. The white part is limestone, the green shades proceed from serpentine and asbestos. There are several fine varieties of marble in Derbyshire; the mottled-gray in the neighbourhood of Moneyash, the light gray being rendered extremely beautiful by the number of purple veins which spread upon its polished surface in elegant irregular branches; but its chief ornament is the multitude of entrochi, with which this transition limestone-marble abounds. Much of the transition and carboniferous limestone of Wales and Westmoreland is capable of being worked up into agreeable dark marbles.

In Scotland, a particularly fine variety of white marble is found in immense beds, at Assynt in Sutherlandshire. A beautiful ash-gray marble of a very uniform grain, and susceptible of a fine polish, occurs on the north side of the ferry of Ballachulish in Invernesshire. One of the most beautiful varieties is that from the hill of Belephetrich in Tiree, one of the Hebrides. Its colours are pale blood-red, light flesh-red, and reddish-white, with dark green particles of hornblende, or rather sahlite, diffused through the general base. The compact marble of Iona is of a fine grain, a dull white colour, somewhat resembling pure compact felspar. It is said by Bournon, to consist of an intimate mixture of tremolite and carbonate of lime, sometimes with yellowish or greenish-yellow spots. The carboniferous limestone of many of the coal basins in the lowlands of Scotland may be worked into a tolerably good marble for chimney-pieces.

In Ireland, the Kilkenny marble is the one best known, having a black ground more or less varied with white marks produced by petrifactions. The spar which occupies the place of the shells, sometimes assumes a greenish-yellow colour. An exceedingly fine black marble has also been raised at Crayleath in the county of Down. At Louthlougher, in the county of Tipperary, a fine purple marble is found, which when polished looks very beautiful. The county of Kerry affords several variegated marbles, not unlike the Kilkenny.

France possesses a great many marble quarries which have been described by Brard, and of which a copious abstract is given under the article marble,--Rees’ Cyclopedia.

The territory of Genoa furnishes several beautiful varieties of marble, the most remarkable of which is the polzevera di Genoa, called in French the vert d’Egypte and vert de mer. It is a mixture of granular limestone with a talcose and serpentine substance disposed in veins; and it is sometimes mixed with a reddish body. This marble was formerly much employed in Italy, France, and England, for chimney-pieces, but its sombre appearance has put it out of fashion.

Corsica possesses a good statuary marble of a fine close grain, and pure milky whiteness, quarried at Ornofrio; it will bear comparison with that of Carrara; also a gray marble (bardiglio), a cipolin, and some other varieties. The island of Elba has immense quarries of a white marble with blackish-green veins.

Among the innumerable varieties of Italian marbles, the following deserve especial notice.

The rovigio, a white marble found at Padua; the white marble of St. Julien, at Pisa, of which the cathedral and celebrated slanting tower are built; the Biancone marble, white with a tinge of gray, quarried at Magurega for altars and tombs. Near Mergozza the white saline marble with gray veins is found, with which the cathedral of Milan is built. The black marble of Bergamo is called paragone, from its black colour, like touchstone; it has a pure intense tint, and is susceptible of a fine polish. The pure black marble of Como is also much esteemed. The polveroso of Pistoya, is a black marble sprinkled with dots; and the beautiful white marble with black spots, from the Lago Maggiore, has been employed for decorating the interior of many churches in the Milanese. The Margorre marble found in several parts of the Milanese, is bluish veined with brown, and composes part of the dome of the cathedral of Milan. The green marble of Florence owes its colour to a copious admixture of steatite. Another green marble, called verde di Prado, occurs in Tuscany, near the little town of Prado. It is marked with spots of a deeper green than the rest, passing even into blackish-blue. The beautiful Sienna marble, or brocatello di Siena, has a yellow colour like the yolk of an egg, which is disposed in large irregular spots, surrounded with veins of bluish-red, passing sometimes into purple. At Montarenti, two leagues from Sienna, another yellow marble is met with, which is traversed by black and purplish-black veins. The Brema marble is yellow with white spots. The mandelato of the Italians is a light red marble with yellowish-white spots, found at Luggezzana, in the Veronese. The red marble of Verona is of a red rather inclining to yellow or hyacinth; a second variety of a dark red, composes the vast amphitheatre of Verona. Another marble is found near Verona, with large white spots in a reddish and greenish paste. Very fine columns have been made of it. The occhio di pavone is an Italian shell marble, in which the shells form large orbicular spots, red, white, and bluish. A madreporic marble known under the name of pietra stellaria, much employed in Italy, is entirely composed of star madrepores, converted into a gray and white substance, and is susceptible of an excellent polish. The village of Bretonico, in the Veronese, furnishes a splendid breccia marble, composed of yellow, steel-gray, and rose-coloured spots. That of Bergamo consists of black and gray fragments in a greenish cement. Florence marble, called also ruin and landscape marble, is an indurated calcareous marl.

Sicily abounds in marbles, the most valuable of which is that called by the English stone-cutters, Sicilian jasper; it is red with large stripes like ribands, white, red, and sometimes green, which run zigzag with pretty acute angles.

Among the Genoese marbles we may notice the highly esteemed variety called portor, on account of the brilliant yellow veins in a deep black ground. The most beautiful kind comes from Porto-Venese, and Louis XIV. caused a great deal of it to be worked up for the decoration of Versailles. It costs now two pounds per cubic foot.

Of cutting and polishing marble.--The marble saw is a thin plate of soft iron, continually supplied during its sawing motion, with water and the sharpest sand. The sawing of moderate pieces is performed by hand, but that of large slabs is most economically done by a proper mill.

The first substance used in the polishing process is the sharpest sand, which must be worked with till the surface becomes perfectly flat. Then a second, and even a third sand of increasing fineness is to be applied. The next substance is emery of progressive degrees of fineness, after which tripoli is employed; and the last polish is given with tin-putty. The body with which the sand is rubbed upon the marble, is usually a plate of iron; but for the subsequent process, a plate of lead is used with fine sand and emery. The polishing rubbers are coarse linen cloths, or bagging, wedged tight into an iron planing tool. In every step of the operation, a constant trickling supply of water is required.

Visiters of Derby may have an opportunity of inspecting Brown’s extensive machinery for cutting marble into many ornamental forms, which has been well described in Rees’ Cyclopedia.

Sir James Jelf patented, in 1822, a combination of machinery for cutting any description of parallel mouldings upon marble slabs, for ornamental purposes; in which, tools, supplied with sand and water, are made to traverse to and fro.

Mr. Tullock obtained a patent, in 1824, for improvements in machinery for sawing and grooving marble; the power being applied by means of toothed wheels bearing cranks, which gave the see-saw motion to the cutting iron plates.

In November, 1829, Mr. Gibbs secured, by patent, an invention for working ornamental devices in marble, by means of a travelling drill, guided by a mould of wood, &c., in counter relief; and in April, 1833, Mr. G. W. Wilds obtained a patent for machinery, which consists of a series of circular cutters, for separating slabs from a block of marble; the block being advanced slowly to meet the cutters, by the progressive movement of a platform upon wheels, driven by the agency of a rack and pinion, as in the cylinder boring machine of the steam-engine manufacturer. Sand and water must be supplied, of course, from a hopper, to these smooth cutting discs of iron or copper. See GLASS-CUTTING. He proposes also to mould and polish marble, by applying a rotatory wheel or cylinder of any shape to it, in its carrying frame.

MARCASITE, is a variety of iron pyrites, containing generally a little arsenic.

MARGARATES, are saline compounds of margaric acid with the bases.

MARGARIC ACID, is one of the acid fats, produced by saponifying tallow with alkaline matter, and decomposing the soap with dilute acid. The term Margaric signifies PEARLY-looking.

The physical properties of the margaric and stearic acids are very similar; the chief difference is that the former is more fusible, melting at 140° F. The readiest mode of obtaining pure margaric acid, is to dissolve olive oil soap in water, to pour into the solution, a solution of neutral acetate of lead, to wash and dry the precipitate, and then to remove its oleate of lead by ether, which does not affect its margarate of lead. The residuum being decomposed by boiling hot muriatic acid, affords margaric acid. When heated in a retort this acid boils. It is insoluble in water, very soluble in alcohol and ether; it reddens litmus paper, and decomposes with the aid of heat, the carbonates of soda and potash.

MARINE ACID. See MURIATIC ACID.

MARINE SALT. See SALT.

MARL (Marne, Fr.; Mergel, Germ.), is a mixed earthy substance, consisting of carbonate of lime, clay, and siliceous sand, in very variable proportions; it is sometimes compact, sometimes pulverulent. According to the predominance of one or other of these three main ingredients, marls may be distributed into calcareous, clayey, and sandy. See LIMESTONE.

MARQUETRY, is a peculiar kind of cabinet work, in which the surface of wood is ornamented with inlaid pieces of various colours and forms. The marqueteur puts gold, silver, copper, tortoise-shell, mother-of-pearl, ivory, horn, &c. under contribution. These substances being reduced to laminæ of proper thinness, are cut out into the desired forms by punches, which produce at once the full pattern or mould, and the empty one, which enclosed it; and both serve their separate purposes in marquetry. For the methods of dyeing the woods, &c. see IVORY.

MARTIAL, signifies belonging to iron; from Mars, the mythological name of this metal.

MASSICOT, is the yellow oxide of lead.

MASTIC (Eng. and Fr.; Mastix, Germ.), is a resin produced by making incisions in the Pistacia Lentiscus, a tree cultivated in the Levant, and chiefly in the island of Chios. It comes to us in yellow, brittle, transparent, rounded tears; which soften between the teeth; with bitterish taste and aromatic smell, and a specific gravity of 1·07. Mastic consists of two resins; one soluble in dilute alcohol; but both dissolve in strong alcohol. Its solution in spirit of wine constitutes a good varnish. It dissolves also in oil of turpentine. See VARNISH.

MATRASS, is a bottle with a thin egg-shaped bottom, much used for digestions in chemical researches.

MATTE, is a crude black copper reduced, but not refined from sulphur and other heterogeneous substances.

MEADOW ORE, is conchoidal bog iron ore.

MEDALS. For their composition, see BRONZE and COPPER.

MEERSCHAUM (Germ.; sea-froth, Eng.; Ecume de Mer, Magnésie carbonatée silicifère, Fr.), is a white mineral, of a somewhat earthy appearance, always soft, but dry to the touch, and adhering to the tongue. Specific gravity, 2·6 to 3·4; affords water by calcination; fuses with difficulty at the blowpipe into a white enamel; and is acted upon by acids. It consists, according to Klaproth, of silica, 41·5; magnesia, 18·25; water and carbonic acid, 39. Other analysts give, silica 50, magnesia 25, water 25. It occurs in veins or kidney-shaped nodules, among rocks of serpentine, at Egribos, in the island of Negropont, Eski-Schehir in Anatolia, Brussa at the foot of Mount Olympus, at Baldissero in Piedmont, in the serpentine veins of Cornwall, &c.

When first dug up, it is soft, greasy, and lathers like soap; and is on that account used by the Tartars in washing their linen. The well-known Turkey tobacco-pipes are made from it, by a process analogous to that for making pottery ware. The bowls of the pipes, when imported into Germany, are prepared for sale by soaking them first in tallow, then in wax, and finally by polishing them with shave-grass.

MELLITE. (Eng. and Fr.; Honigstein, Germ.) See HONEYSTONE.

MELLITIC ACID, which is associated with alumina in the preceding mineral, crystallizes in small colourless needles, is without smell, of a strongly acid taste, permanent in the air, soluble in water and alcohol, as also in boiling hot concentrated sulphuric acid, but is decomposed by hot nitric acid, and consists of 50·21 carbon, and 49·79 oxygen. It is carbonized at a red heat, without the production of any inflammable oil.

MELLON, is a new compound of carbon and azote, discovered by M. Liebig, by heating bi-sulpho-cyanide of mercury. The mellon remains at the bottom of the retort under the form of a yellow powder.

MENACHANITE, an ore of titanium, found in the bed of a rivulet which flows into the valley Menacan, in Cornwall.

MERCURY or QUICKSILVER. This metal is distinguished by its fluidity at common temperatures; its density = 13·6; its silver blue lustre; and its extreme mobility. A cold of 39° below zero of Fahrenheit, or -40° cent., is required for its congelation, in which state its density is increased in the proportion of 10 to 9, or it becomes of spec. grav. 15·0. At a temperature of 656° F. it boils and distils off in an elastic vapour; which, being condensed by cold, forms purified mercury.

Mercury combines with great readiness with certain metals, as gold, silver, zinc, tin, and bismuth, forming, in certain proportions, fluid solutions of these metals. Such mercurial alloys are called amalgams. This property is extensively employed in many arts; as in extracting gold and silver from their ores; in gilding, plating, making looking-glasses, &c. Humboldt estimates at 16,000 quintals, of 100 lbs. each, the quantity of mercury annually employed at his visit to America, in the treatment of the mines of New Spain; three-fourths of which came from European mines.

The mercurial ores may be divided into four species:--

1. Native quicksilver.--It occurs in most of the mines of the other mercurial ores, in the form of small drops attached to the rocks, or lodged in the crevices of other ores.

2. Argental mercury, or native silver amalgam.--It has a silver-white colour, and is more or less soft, according to the proportion which the mercury bears to the silver. Its density is sometimes so high as 14. A moderate heat dissipates the mercury, and leaves the silver. Klaproth states its constituents at silver 36, and mercury 64, in 100; but Cordier makes them to be, 27-1/2 silver, and 72-1/2 mercury. It occurs crystallized in a variety of forms. It has been found in the territory of Deux-Ponts, at Rozenau and Niderstana, in Hungary, in a canton of Tyrol, at Sahlberg in Sweden, at Kolyvan in Siberia, and at Allémont in Dauphiny; in small quantity at Almaden in Spain, and at Idria in Carniola. By the chemical union of the mercury with the silver, the amalgam, which should by calculation have a spec. grav. of only 12·5, acquires that of 14·11, according to M. Cordier.

3. Sulphuret of mercury, commonly called Cinnabar, is a red mineral of various shades; burning at the blowpipe with a blue flame, volatilizing entirely with the smell of burning sulphur, and giving a quicksilver coating to a plate of copper held in the fumes. Even the powder of cinnabar rubbed on copper whitens it. Its density varies from 6·9 to 10·2. It becomes negatively electrical by friction. Analysed by Klaproth, it was found to consist of mercury 84·5, sulphur 14·75. Its composition, viewed as a bisulphuret of mercury, is, mercury 86·2, sulphur 13·8. The finest crystals of sulphuret of mercury come from China, and Almaden in Spain. These contain, according to Klaproth, 85 per cent. of mercury.

A bituminous sulphuret of mercury appears to be the base of the great exploration of Idria; it is of a dark liver-red hue; and of a slaty texture, with straight or twisted plates. It exists in large masses in the bituminous schists of Idria. M. Beurard mentions also the locality of Munster-Appel, in the duchy of Deux-Ponts, where the ore includes impressions of fishes, curiously spotted with cinnabar.

The compact variety of the Idria ore seems very complex in composition, according to the following analysis of Klaproth:--Mercury, 81·8; sulphur, 13·75; carbon, 2·3; silica, 0·65; alumina, 0·55; oxide of iron, 0·20; copper, 0·02; water, 0·73; in 100 parts. M. Beurard mentions another variety from the Palatinate, which yields a large quantity of bitumen by distillation; and it was present in all the specimens of these ores analyzed by me for the German Mines Company. At Idria and Almaden the sulphurets are extremely rich in mercury.

4. Muriated mercury, or the Chloride of mercury, commonly called Horn mercury. This ore occurs in very small crystals of a pearl-gray or greenish-gray colour, or in small nipples which stud, like crystals, the cavities, fissures, or geodes among the ferruginous gangues of the other ores of mercury. It is brittle, and entirely volatile at the blowpipe, characters which distinguish it from horn silver.

The geological position of the mercurial ores, in all parts of the world, is in the strata which commence the series of secondary formations. Sometimes they are found in the red sandstone above the coal, as at Menildot, in the old dutchy of Deux-Ponts, at Durasno in Mexico, at Cuença in New Granada, at Cerros de Gauzan and Upar in Peru; in the subordinate porphyries, as at Deux-Ponts, San Juan de la Chica in Peru, and at Cerro-del-Fraile, near the town of San-Felipe, they occur also among the strata below, or subordinate to the calcareous formation, called zechstein, in Germany, or among the accompanying bituminous schists, as at Idria in Carniola; and, lastly, they form masses in the zechstein itself. Thus, it appears that the mercurial deposits are confined within very narrow geological limits, between the calcareous beds of zechstein, and the red sandstone. They occur at times in carbonaceous nodules, derived from the decomposition of mosses of various kinds; and the whole mercurial deposit is occasionally covered with beds of charcoal, as at Durasno.

They are even sometimes accompanied with the remains of organic bodies, such as casts of fishes, fossil shells, silicified wood, and true coal. The last fact has been observed at Potzberg, in the works of Drey-Koenigszug, by M. Brongniart. These sandstones, bituminous schists, and indurated clays, contain mercury both in the state of sulphuret and in the native form. They are more or less penetrated with the ore, forming sometimes numerous beds of very great thickness; while, in the more antient or the primitive formations, these ores exist only in very small quantity associated with tin. Mercury is, generally speaking, a metal sparingly distributed in nature, and its mines are very rare.

The great exploitations of Idria in Friuli, in the county of Goritz, were discovered in 1497, and the principal ore mined there is the bituminous sulphuret. The workings of this mine have been pushed to the depth of 280 yards. The product in quicksilver might easily amount annually to 6000 metric quintals = 600 tons British; but, in order to uphold the price of the metal, the Austrian government has restricted the production to 150 tons. The memorable fire of 1803 was most disastrous to these mines. It was extinguished only by drowning all the underground workings. The sublimed mercury in this catastrophe occasioned diseases and nervous tremblings to more than 900 persons in the neighbourhood.

Pliny has recorded two interesting facts: 1. that the Greeks imported red cinnabar from Almaden 700 years before the Christian era; and 2. that Rome, in his time, annually received 700,000 pounds from the same mines. Since 1827, they have produced 22,000 cwts. of mercury every year, with a corps of 700 miners and 200 smelters; and, indeed, the veins are so extremely rich, that though they have been worked pretty constantly during so many centuries, the mines have hardly reached the depth of 330 yards, or something less than 1000 feet. The lode actually under exploration is from 14 to 16 yards thick, and it becomes thicker still at the crossing of the veins. The totality of the ore is extracted. It yields in their smelting works only 10 per cent. upon an average, but there is no doubt, from the analysis of the ores, that nearly one half of the quicksilver is lost, and dispersed in the air, to the great injury of the workmen’s health, in consequence of the barbarous apparatus of aludels employed in its sublimation; an apparatus which has remained without any material change for the better since the days of the Moorish dominion in Spain. M. Le Play, the eminent Ingenieur des Mines, who published, in a recent volume of the Annales des Mines, his Itinéraire to Almaden, says, that the mercurial contents of the ores are notablement plus elevées than the product.

These veins extend all the way from the town of Chillon to Almadenejos. Upon the borders of the streamlet Balde Azogues, a black slate is also mined which is abundantly impregnated with metallic mercury. The ores are treated in 13 double furnaces, which I shall presently describe. “Le mercure,” says M. Le Play, “a sur la santé des ouvriers la plus funeste influence, et l’on ne peut se défendre d’un sentiment pénible en voyant l’empressement avec lequel des jeunes gens, pleins de force et de santé, se disputent la faveur d’aller chercher dans les mines, des maladies cruelles, et souvent une mort prématurée. La population des mineurs d’Almaden méritent le plus haut interêt.” These victims of a deplorable mismanagement are described as being a laborious, simple-minded, virtuous race of beings, who are thus condemned to breathe an atmosphere impregnated far and near with the fumes of a volatile poison, which the lessons of science, as I shall presently demonstrate, might readily repress, with the effect of not only protecting the health of the population, but of vastly augmenting the revenues of the state.

These celebrated mines, near to which lie those of Las Cuebas and of Almadenejos, were known to the Romans. After having been the property of the religious knights of Calatrava, who had assisted in expelling the Moors, they were farmed off to the celebrated Fugger merchants of Augsbourg; and afterwards explored on account of the government, from the date of 1645 till the present time. Their produce was, till very lately, entirely appropriated to the treatment of the gold and silver ores of the new world.

The mines of the Palatinate, situated on the left bank of the Rhine, though they do not approach in richness and importance to those of Idria and Almaden, merit, however, all the attention of the government that farms them out. They are numerous, and varied in geological position. Those of Drey-Koenigszug, at Potzberg, near Kussel, deserve particular notice. The workings have reached a depth of more than 220 yards; the ore being a sandstone strongly impregnated with sulphuret of mercury. The produce of these mines is estimated at about 30 tons per annum.

There are also in Hungary, Bohemia, and several other parts of Germany, some inconsiderable exploitations of mercury, the total produce of which is valued at about 30 or 40 tons on an average of several years.

The mines of Guancavelica, in Peru, are the more interesting, as their products are directly employed in treating the ores of gold and silver, which abound in that portion of America. These quicksilver mines, explored since 1570, produced, up to 1800, 53,700 tons of that metal; but the actual produce of the explorations of these countries was, according to Helms, about the beginning of this century, from 170 to 180 tons per annum.

In 1782 recourse was had by the South American miners to the mercury extracted in the province of Yun-nan, in China.

The metallurgic treatment of the quicksilver ores is tolerably simple. In general, when the sulphuret of mercury, the most common ore, has been pulverized, and sometimes washed, it is introduced into retorts of cast iron, sheet iron, or even stoneware, in mixture with an equal weight of quicklime. These retorts are arranged in various ways.

Prior to the 17th century, the method called per descensum was the only one in use for distilling mercury; and it was effected by means of two earthen pots adjusted over each other. The upper pot, filled with ore, and closed at the top, was covered over with burning fuel; and the mercurial vapours expelled by the heat, passed down through small holes in the bottom of the pot, to be condensed in another vessel placed below. However convenient this apparatus might be, on account of the facility of transporting it, wherever the ore was found, its inefficiency and the losses it occasioned were eventually recognized. Hence, before 1635, some smelting works of the Palatinate had given up the method per descensum, which was, however, still retained in Idria; and they substituted for it the furnaces called galleries. At first earthenware retorts were employed in these furnaces; but they were soon succeeded by iron retorts. In the Palatinate this mode of operating is still in use. At Idria, in the year 1750, a great distillatory apparatus was established for the treatment of the mercurial ores, in imitation of those which previously existed at Almaden, in Spain, and called aludel-furnaces. But, since 1794, these aludels have been suppressed, and new distillatory apparatus have been constructed at Idria, remarkable only for their magnitude; exceeding, in this respect, every other metallurgic erection.

There exist, therefore, three kinds of apparatus for the distillation of mercury: 1. the furnace called a gallery; 2. the furnace with aludels; and 3. the large apparatus of Idria. I shall describe each of these briefly, in succession.

1. Furnace called Gallery of the Palatinate.--The construction of this furnace is disposed so as to contain four ranges, a a´, b b´, of large retorts, styled cucurbits, of cast iron, in which the ore of mercury is subjected to distillation. This arrangement is shewn in fig. 656., which presents a vertical section in the line a b of the ground plan, fig. 657. In the ground plan, the roof e e´ of the furnace (fig. 656.) is supposed to be lifted off, in order to shew the disposition of the four ranges of cucurbits upon the grate c f, figs. 656, 657., which receives the pit-coal employed as fuel. Under this grate extends an ash-pit d. Fig. 658., which exhibits an elevation of the furnace, points out this ash-pit, as well as one of the two doors c, by which the fuel is thrown upon the grate c f. Openings e e, (fig. 656.) are left over the top arch of the furnace, whereby the draught of air may receive a suitable direction. The grate of the fire-place extends over the whole length of the furnace, fig. 657., from the door c to the door f, situated at the opposite extremity. The furnace called gallery includes commonly 30 cucurbits, and in some establishments even 52. Into each are introduced from 56 to 70 pounds of ore, and 15 to 18 pounds of quicklime, a mixture which fills no more than two-thirds of the cucurbit; to the neck a stoneware receiver is adapted, containing water to half its height. The fire, at first moderate, is eventually pushed till the cucurbits are red hot. The operation being concluded, the contents of the receivers are poured out into a wooden bowl placed upon a plank above a bucket; the quicksilver falls to the bottom of the bowl, and the water draws over the black mercury, for so the substance that coats the inside of the receivers is called. This is considered to be a mixture of sulphuret and oxide of mercury. The black mercury, taken out of the tub and dried, is distilled anew with excess of lime; after which the residuum in the retorts is thrown away, as useless.

Aludel furnaces of Almaden.--Figs. 659. and 660. represent the great furnaces with aludels in use at Almaden, and anciently in Idria; for between the two establishments there was in fact little difference before the year 1794. Figs. 659. and 662. present two vertical sections; figs. 660. and 661. are two plans of two similar furnaces, conjoined in one body of brickwork. In the four figures the following objects are to be remarked; a door a, by which the wood is introduced into the fire-place b. This is perforated with holes for the passage of air; the ash-pit c, is seen beneath. An upper chamber d, contains the mercurial ores distributed upon open arches, which form the perforated sole of this chamber. Immediately over these arches, there are piled up in a dome form, large blocks of a limestone, very poor in quicksilver ore; above these are laid blocks of a smaller size, then ores of rather inferior quality, and stamped ores mixed with richer minerals. Lastly, the whole is covered up with soft bricks, formed of clay kneaded with schlich, and with small pieces of sulphuret of mercury. Six ranges of aludels or stoneware tubes, f f, of a pear shape, luted together with clay, are mounted in front of each of the two furnaces, on a double sloping terrace, having in its lowest middle line two gutters t v, a little inclined towards the intermediate wall m. In each range the aludel placed at the line t m v of fig. 660., that is to say at the lowest point, g, figs. 659. 662., is pierced with a hole. Thereby the mercury which had been volatilized in d, if it be already condensed by the cooling in the series of aludels f g, may pass into the corresponding gutter, next into the hole m, fig. 660., and after that into the wooden pipes h h´, fig. 659., which conduct it across the masonry of the terrace into cisterns filled with water; see q, fig. 661., which is the plan of fig. 662.

The portion of mercury not condensed in the range of aludels, f g, which is the most considerable, goes in the state of vapour, into a chamber k; but in passing under a partition l l, a certain portion is deposited in a cistern i, filled with water. The greater part of the vapours diffused in the chamber k´ is thereby condensed, and the mercury falls down upon the two inclined planes which form its bottom. What may still exist as vapour passes into an upper chamber k´, by a small chimney n. On one of the sides of this chamber there is a shutter which may be opened at pleasure from below upwards, and beneath this shutter, there is a gutter into which a notable quantity of mercury collects. Much of it is also found condensed in the aludels. These facts prove that this process has inconveniences, which have been tried to be remedied by the more extensive but rather unchemical grand apparatus of Idria.

Details of the aludel apparatus: 25 are set in each of the 12 ranges, seen in fig. 661. constituting 300 pear-shaped stoneware vessels, open at both ends, being merely thrust into one another, and luted with loam. What a multitude of joints, of which a great many must be continually giving way by the shrinkage of the luting, whereby the mercurial fumes will escape with great loss of product, to poison the air!

a, is the door of the fire-place; c, the perforated arches upon which the ore is piled in the chamber e, through the door d, and an orifice at top; the latter being closed during the distillation; f f are vents for conducting the mercurial vapours into two chambers i, separated by a triangular body of masonry m n; h is the smoke chimney of the fire-place; o o, are the ranges of aludels, in connection with the chamber i, which are laid slantingly towards the gutter q, upon the double inclined plane terrace, and terminate in the chamber h q; this being surmounted by two chimneys t. The mercury is collected in these aludels and in the basins at q and p, fig. 661. r is a thin stone partition set up between the two principal walls of each of the furnaces. v is the stair of the aludel terrace, leading to the platform which surmounts the furnace; z is a gutter for conducting away the rains which may fall upon the buildings.

Great apparatus of Idria.--Before entering into details of this laboratory, it will not be useless to recapitulate the metallurgic classification of the ores treated in it. 1. The ores in large blocks, fragments, or shivers, whose size varies from a cubic foot to that of a nut. 2. The smaller ores, from the size of a nut to that of grains of dust.

The first class of large ores comprises three subdivisions, namely; a, blocks of metalliferous rocks, which is the most abundant and the poorest species of ore, affording only one per cent. of mercury; b, the massive sulphuret of mercury, the richest and rarest ore, yielding 80 per cent. when it is picked; c, the fragments or splinters proceeding from the breaking and sorting, and which vary in value, from 1 to 40 per cent.

The second class of small ores comprises: d, the fragments or shivers extracted from the mine in the state of little pieces, affording from 10 to 12 per cent.; e, the kernels of ore, separated on the sieve, yielding 32 per cent.; f, the sands and paste called schlich, obtained in the treatment of the poorest ores, by means of the stamps and washing tables; 100 parts of this schlich give at least 8 of quicksilver.

The general aspect of the apparatus is indicated by figs. 663, 664. and 665. Fig. 665. represents the exterior, but only one half, which is enough, as it resembles exactly the other, which is not shown. In these three figures the following objects may be distinguished; figs. 663, 664., a, door of the fire-place; b, the furnace in which beech-wood is burned mixed with a little fir-wood; c, door of the ash-pit, extended beneath; d, a space in which the ores are deposited upon the seven arches, 1. to 7., as indicated in figs. 663. and 666.; e e, brick tunnels, by which the smoke of the fuel and the vapours of mercury pass, on the one side, into successive chambers f k.

f g h i j k l are passages which permit the circulation of the vapours from the furnace a b c d, to the chimneys l l. Figs. 663. and 664. exhibit clearly the distribution of these openings on each side of the same furnace, and in each half of the apparatus, which is double, as fig. 664. shows; the spaces without letters being in every respect similar to the spaces mentioned below. Fig. 664. is double the scale of fig. 663.

m m´, fig. 664., are basins of reception, distributed before the doors of each of the chambers f k f´ k´. The condensed mercury which flows out of the chambers is conveyed thither. n n´ is a trench into which the mercury, after being lifted into the basins m, is poured, so that it may run towards a common chamber o, in the sloping direction indicated by the arrows. o leads to the chamber where the mercury is received into a porphyry trough; out of which it is laded and packed up in portions of 50 or 100 lbs. in sheep-skins prepared with alum. p p´, fig. 663., are vaulted arches, through which a circulation may go on round the furnace a b c d, on the ground level, q q´ are the vaults of the upper stories. r r´, fig. 665., vaults which permit access to the tunnels e´ e´´, fig. 663.

s s´ and t t´, fig. 665., are the doors of the chambers, f k and f´ k´. These openings are shut during the distillation by wooden doors faced with iron, and luted with a mortar of clay and lime. u u´ is the door of the vaults 1. to 7. of the furnace represented in fig. 663. These openings are hermetically shut, like the preceding. v v´, fig. 663., are superior openings of the chambers, closed during the operation by luted plugs; they are opened afterwards to facilitate the cooling of the apparatus, and to collect the mercurial soot. x y z, fig. 666., are floors which correspond to the doors u u´ of the vaults 1. to 7., fig. 665. These floors are reached by stairs set up in the different parts of the building, which contains the whole apparatus.

On the lower arches the largest blocks of metalliferous rock are laid; over these the less bulky fragments are arranged, which are covered with the shivers and pieces of less dimension. On the middle vaults, the small ore is placed, distributed into cylindrical pipkins of earthenware, of 10 inches diameter and 5 inches depth. The upper vaults receive likewise pipkins filled with the sands and pastes called schlich.

In 3 hours, by the labour of 40 men, the two double sets of apparatus are charged, and all the apertures are closed. A quick fire of beech-wood is then kindled; and when the whole mass has become sufficiently heated, the sulphuret of mercury begins to vapourize; coming into contact with the portion of oxygen which had not been carbonated, by combustion, its sulphur burns into sulphurous acid, while the mercury becomes free, passes with the other vapours into the chambers for condensing it, and precipitates in the liquid form at a greater or less distance from the fire-place. The walls of the chambers and the floors, with which their lower portion is covered, are soon coated over with a black mercurial soot, which, being treated anew, furnishes 50 per cent. of mercury. The distillation lasts from 10 to 12 hours; during which time the whole furnace is kept at a cherry-red heat. A complete charge for the two double apparatus, consists of from 1000 to 1300 quintals of ore, which produce from 80 to 90 quintals of running mercury. The furnace takes from 5 or 6 days to cool, according to the state of the weather; and if to that period be added the time requisite for withdrawing the residuums, and attending to such repairs as the furnace may need, it is obvious that only one distillation can be performed in the course of a week.

In the works of Idria, in 1812, 56,686 quintals and a half of quicksilver ores were distilled, after undergoing a very careful mechanical preparation. They afforded 4832 quintals of running mercury; a quantity corresponding to about 8-1/2 per cent. of the ore. These smelting works are about 180 feet long and 30 feet high.

Upon the preceding three systems of smelting mercurial ores, I shall now make some observations.

It has been long well known, that quicksilver may be most readily extracted from cinnabar, by heating it in contact with quicklime. The sulphur of the cinnabar combines, by virtue of a superior affinity with the lime, to the exclusion of the quicksilver, to form sulphurets of lime and calcium, both of which being fixed hepars, remain in the retort while the mercury is volatilized by the heat. In a few places, hammerschlag, or the iron cinder, driven off from the blooms by the tilting hammer, has been used instead of lime in the reduction of this mercurial ore, whereby sulphurous acid and sulphuret of iron are formed.

The annual production of the Bavarian Rhine provinces has been estimated at from 400 to 550 quintals; that of Almaden, in the year 1827, was 22,000 quintals; and of Idria, at present, is not more than 1500 quintals.

All the plans hitherto prescribed for distilling the ore along with quicklime, are remarkably rude. In that practised at Landsberg by Obermoschel, there is a great waste of labour, in charging the numerous small cucurbits; there is a great waste of fuel in the mode of heating them; a great waste of mercury by the imperfect luting of the retorts to the receivers, as well as the imperfect condensation of the mercurial vapours; and probably a considerable loss by pilfering.

The modes practised at Almaden and Idria are, in the greatest degree, barbarous; the ores being heated upon open arches, and the vapours attempted to be condensed by enclosing them within brick or stone and mortar walls, which can never be rendered either sufficiently tight or cool.

To obviate all these inconveniences and sources of loss, the proper chemical arrangements suited to the present improved state of the arts ought to be adopted, by which labour, fuel, and mercury, might all be economized to the utmost extent. The only apparatus fit to be employed is a series of cast-iron cylinder retorts, somewhat like those employed in the coal gas works, but with peculiarities suited to the condensation of the mercurial vapours. Into each of these retorts, supposed to be at least one foot square in area, and 7 feet long, 6 or 7 cwt. of a mixture of the ground ore with the quicklime, may be easily introduced, from a measured heap, by means of a shovel. The specific gravity of the cinnabar being more than 6 times that of water, a cubic foot of it will weigh more than 3-1/2 cwt.; but supposing the mixture of it with quicklime (when the ore does not contain the calcareous matter itself) to be only thrice the density of water, then four cubic feet might be put into each of the above retorts, and still leave 1-1/2 cubic feet of empty space for the expansion of volume which may take place in the decomposition. The ore should certainly be ground to a moderately fine powder, by stamps, iron cylinders, or an edge wheel, so that when mixed with quicklime, the cinnabar may be brought into intimate contact with its decomposer, otherwise much of it will be dissipated unproductively in fumes, for it is extremely volatile.

Figs. 667, 668, 669. represent a cheap and powerful apparatus which I contrived at the request of the German Mines Company of London, and which is now mounted at Landsberg, near Obermoschel, in the Bavarian Rhein-Kreis.

Fig. 667. is a section parallel to the front elevation of three arched benches of retorts, of the size above specified. Each bench contains 3 retorts, of the form represented by a a a. I, is the single fire-place or furnace, capable of giving adequate ignition by coal or wood, to the three retorts. The retorts were built up in an excellent manner, by an English mason perfectly acquainted with the best modes of erecting coal-gas retorts, who was sent over on purpose. The path of the flame and smoke is precisely similar to that represented in fig. 483, page 549, whereby the uppermost retort is immersed in a bath of uniformly ignited air, while the currents reverberated from the top, play round the two undermost retorts, in their way to the vent-flues beneath them. The bottom of the uppermost retort is protected from the direct impulse of the flame by fire-tiles. The dotted lines K K, show the paths of the chimneys which rise at the back ends of the retorts.

In the section, fig. 668., a is the body of the retort; its mouth at the right hand end is shut, as usual, by a luted iron lid, secured with a cross-bar and screw-bolts; its other end is prolonged by a sloping pipe of cast iron, 4 inches in diameter, furnished with a nozzle hole at L, closed with a screw plug. Through this hole a wire rammer may be introduced, to ascertain that the tube is pervious, and to cleanse it from the mercurial soot, when thought necessary. c, is a cross section of the main condenser, shown in a longitudinal section at C C, fig. 669. This pipe is 18 inches in diameter, and about 20 feet long. At a a, &c., the back ends of the retorts are seen, with the slanting tubes b b, &c., descending through orifices in the upper surface of the condenser pipe, and dipping their ends just below the water-line h i. g, is the cap of a water valve, which removes all risk from sudden expansion or condensation. The condenser is placed within a rectangular trough, made either of wood or stone, through which a sufficient stream of water passes to keep it perfectly cool, and repress every trace of mercurial vapour, and it is laid with a slight inclination from i to h, so that the condensed quicksilver may spontaneously flow along its bottom, and pass through the vertical tube D into the locked up iron chest, or magazine e. This tube D is from the beginning closed at bottom, by immersion in a shallow iron cup, always filled with mercury. k is a graduated gauge rod, to indicate the progressive accumulation of quicksilver in the chest, without being under the necessity of unlocking it.

This air-tight apparatus was erected about a year ago, and has been found to act perfectly well; I regret, however, that my professional engagements at home have not hitherto permitted me to conduct its operations personally for some days. The average samples of cinnabar ore from Obermoschel are ten times poorer than those of Almaden. Were such an apparatus as the above, with some slight modifications which have lately occurred to me, mounted for the Spanish mines, I am confident that their produce in quicksilver might be nearly doubled, with a vast economy of fuel, labour, and human life. The whole cost of the 9 large retorts, with their condensing apparatus, iron magazine, &c., was very little more than two hundred pounds! As the retorts are kept in a state of nearly uniform ignition, like those of the gas works, neither they, nor the furnaces are liable to be injured in their joints by the alternate contractions and expansions, which they would inevitably suffer if allowed to cool; and being always ready heated to the proper pitch for decomposing the mercurial ores, they are capable of working off a charge, under skilful management, in the course of 3 hours. Thus, in 24 hours, with a relay of labourers, 8 charges of at least 5 cwts. of ore each, might be smelted = 2 tons, with 3 retorts, and 6 tons with 9 retorts; with a daily product from the rich ores of Almaden, or even Idria, of from 12 cwts. to 20 cwts. Instead of 3 benches of 3 retorts each, I would recommend 15 benches, containing 45 retorts, to be erected for either the Almaden or Idria mines; which, while they would smelt all their ores, could be got for a sum not much exceeding 1000_l._, an outlay which they would reimburse within a month or two.

Quicksilver is a substance of paramount value to science. Its great density and its regular rate of expansion and contraction by increase and diminution of temperature, give it the preference over all liquids for filling barometric and thermometric tubes. In chemistry it furnishes the only means of collecting and manipulating, in the pneumatic trough, such gaseous bodies as are condensable over water. To its aid, in this respect, the modern advancement of chemical discovery is pre-eminently due.

This metal alloyed with tin-foil forms the reflecting surface of looking glasses, and by its ready solution of gold or silver, and subsequent dissipation by a moderate heat, it becomes the great instrument of the arts of gilding and silvering copper and brass. The same property makes it so available in extracting these precious metals from their ores. The anatomist applies it elegantly, to distend and display the minuter vessels of the lymphatic system, and secretory systems, by injecting it with a syringe through all their convolutions. It is the basis of many very powerful medicines, at present probably too indiscriminately used, to the great detriment of English society; for it is far more sparingly prescribed by practitioners upon the continent of Europe, not otherwise superior in skill or science to those of Great Britain.

The nitrate of mercury is employed for the secrétage of rabbit and hare-skins, that is, for communicating to the fur of these and other quadrupeds the faculty of felting, which they do not naturally possess. With this view the solution of that salt is applied to them lightly in one direction with a sponge. A compound amalgam of zinc and tin is probably the best exciter which can be applied to the cushions of electrical machines. Mercury imported for home consumption in 1836, 286,808 lbs.; in 1837, 314,036 lbs.

The only mercurial compounds which are extensively used in the arts, are fictitious cinnabar or VERMILLION, and corrosive sublimate.

MERCURY, BICHLORIDE OF; Corrosive sublimate; (Deutochlorure de mercure, Fr.; Aetzendes quecksilber sublimat, Germ.) is made by subliming a mixture of equal parts of persulphate of mercury, prepared as above described, and sea-salt, in a stone-ware cucurbit. The sublimate rises in vapour, and encrusts the globular glass capital with a white mass of small prismatic needles. Its specific gravity is 5·14. Its taste is acrid, stypto-metallic, and exceedingly unpleasant. It is soluble in 20 parts of water, at the ordinary temperature, and in its own weight of boiling water. It dissolves in 2-1/2 times its weight of cold alcohol. It is a very deadly poison. Raw white of egg swallowed in profusion, is the best antidote. A solution of corrosive sublimate has been long employed for preserving soft anatomical preparations. By this means the corpse of Colonel Morland was embalmed, in order to be brought from the seat of war to Paris. His features remained unaltered, only his skin was brown, and his body was so hard as to sound like a piece of wood when struck with a hammer.

In the valuable work upon the dry rot, published by Mr. Knowles, secretary of the committee of inspectors of the navy, in 1821, corrosive sublimate is enumerated among the chemical substances which had been prescribed for preventing the dry rot in timber; and it is well known that Sir H. Davy had, several years before that date, used and recommended to the Admiralty and Navy Board, corrosive sublimate as an anti-dry rot application. It has been since extensively employed by a joint-stock company for the same purpose, under the title of Kyan’s patent.

MERCURY, PROTOCHLORIDE OF; Calomel; (Protochlorure de mercure, Fr., Versüsstes quecksilber, Germ.) This compound, so much used and abused by medical practitioners, is commonly prepared by triturating four parts of corrosive sublimate along with three parts of running quicksilver in a marble mortar, till the metallic globules entirely disappear, with the production of a black powder, which is to be put into a glass balloon, and exposed to a subliming heat in a sand bath. The calomel, which rises in vapour, and attaches itself in a crystalline crust to the upper hemisphere of the balloon, is to be detached, reduced to a fine powder, or levigated and elutriated. 200 lbs. of mercury yield 236 of calomel and 272 of corrosive sublimate.

The following more economical process is that adopted at the Apothecaries’ Hall, London. 140 pounds of concentrated sulphuric acid are boiled in a cast iron pot upon 100 pounds of mercury, till a dry persulphate is obtained. Of this salt, 124 pounds are triturated with 81 pounds of mercury, till the globules disappear, and till a protosulphate be formed. This is to be intimately mixed with 68 pounds of sea-salt, and the mixture, being put into a large stone-ware cucurbit, is to be submitted to a subliming heat. See CALOMEL.

From 190 to 200 pounds of calomel rise in a crystalline cake, as in the former process, into the capital; while sulphate of soda remains at the bottom of the alembic. The calomel must be ground to an impalpable powder, and elutriated. The vapours, instead of being condensed into a cake within the top of the globe or in a capital, may be allowed to diffuse themselves into a close vessel, containing water in a state of ebullition, whereby the calomel is obtained at once in the form of a washed impalpable powder. Calomel is tasteless and insoluble in water. Its specific gravity is 7·176.

For the compound of mercury with fulminic acid, see FULMINATE. Periodide of mercury is a bright but fugitive red pigment. It is easily prepared by dropping a solution of iodide of potassium into a solution of corrosive sublimate, as long as any precipitation takes place, decanting off the supernatant muriate of potash, washing and drying the precipitate.

METALLURGY (Erzkunde, Germ.) is the art of extracting metals from their ores. This art, which supplies industry with the instruments most essential to its wants, is alike dependent upon the sciences of chemistry and mechanics; upon the former, as directing the smelting processes, best adapted to disentangle each metal from its mineralizer; upon the latter, as furnishing the means of grinding the ores, and separating the light stony parts from the rich metallic matter.

Notwithstanding the striking analogy which exists between common chemical and metallurgic operations, since both are employed to insulate certain bodies from others, there are essential differences which should be carefully noted. In the first place, the quantity of materials being always very great in metallurgy, requires corresponding adaptations of apparatus, and often produces peculiar phenomena; in the second place, the agents to be employed for treating great masses, must be selected with a view to economy, as well as to chemical action. In analytical chemistry, the main object being exactness of result, and purity of product, little attention is bestowed upon the value of the reagents, on account of the small quantity required for any particular process. But in smelting metals upon the great scale, profit being the sole object, cheap materials and easy operations alone are admissible.

The metallic ores as presented by nature, are almost always mixed with a considerable number of foreign substances; and could not therefore be advantageously submitted to metallurgic operations, till they are purified and concentrated to a certain degree by various methods.

OF THE PREPARATION OF ORES FOR THE SMELTING HOUSE.

There are two kinds of preparation; the one termed mechanical, from the means employed, and the results obtained, consists in processes for breaking and grinding the ores, and for washing them so as to separate the vein-stones, gangues, or other mixed earthy matters, in order to insulate or concentrate the metallic parts.

Another kind of preparation, called chemical, has for its object to separate, by means of fire, various volatile substances combined in the ores, and which it is requisite to clear away, at least in a certain degree, before trying to extract the metals they may contain.

Lastly, an indispensable operation in several circumstances, is to discover, by simple and cheap methods, called assays, the quantity of metal contained in the different species of ores to be treated.

This head of our subject, therefore, falls under three subdivisions:--

§ 1. The mechanical preparation of ores, including picking, stamping, and different modes of washing.

§ 2. The chemical preparation, consisting especially in the roasting or calcination of the ores.

§ 3. The assay of ores, comprehending the mechanical part: that is, by washing; the chemical part, or assays by the dry way; and the assays by the moist way.

Section 1. Of the mechanical preparation or dressing of ores.--I. The first picking or sorting takes place in the interior, or underground, workings, and consists in separating the fragments of rocks, that apparently contain no metallic matter, from those that contain more or less of it. The external aspect guides this separation; as also the feeling of density in the hand.

The substances when turned out to the day, undergo another sorting, with greater or less care, according to the value of the included metal. This operation consists in breaking the lumps of ore with the hammer, into fragments of greater or less size, usually as large as the fist, whereby all the pieces may be picked out and thrown away that contain no metal, and even such as contain too little to be smelted with advantage. There is for the most part, a building erected near the output of the mine, in which the breaking and picking of the ores are performed. In a covered gallery, or under a shed, banks of earth are thrown up, and divided into separate beds, on each of which a thick plate of cast iron is laid. On this plate, elderly workmen, women, and children, break the ores with hand hammers, then pick and sort them piece by piece. The matters so treated, are usually separated into three parts; 1. the rock or sterile gangue, which is thrown away; 2. the ore for the stamping mill, which presents too intimate a mixture of rock and metallic substance to admit of separation by breaking and picking; and 3. the pure ore, or at least the very rich portion, called the sorted mine or the fat ore. On the sorting floors there remains much small rubbish, which might form a fourth subdivision of ore, since it is treated in a peculiar manner, by sifting, as will be presently mentioned.

The distribution of fragments more or less rich, in one class or another, is relative to the value of the included metal, taking into account the expenses necessary for its extraction. Thus in certain lead mines, pieces of the gangues are thrown away, which judged by the eye may contain 3 per cent. of galena, because it is known that the greater portion of this would be lost in the washings required for separating the 97 parts of the gangue, and that the remainder would not pay the expenses.

II. The very simple operations of picking are common to almost all ores; but there are other operations requiring more skill, care, and expense, which are employed in their final state of perfection only upon ores of metals possessing a certain value, as those of lead, silver, &c. We allude to the washing of ores.

The most simple and economical washings are those that certain iron ores, particularly the alluvial, are subjected to, as they are found near the surface of the ground agglutinated in great or little pieces. It is often useful to clean these pieces, in order to pick out the earthy lumps, which would be altogether injurious in the furnaces.

This crude washing is performed sometimes by men stirring in the midst of a stream of water, with iron rakes or shovels, the lumps of ore placed in large chests, or basins of wood or iron.

In other situations, this washing is executed more economically by a machine called a buddle or dolly-tub by our miners. A trough of wood or iron, with a concave bottom, is filled with the ore to be washed. Within the tub or trough, arms or iron handles are moved round about, being attached to the arbor of a hydraulic wheel. The trough is kept always full of water, which as it is renewed carries off the earthy matters, diffused through it by the motion of the machine, and the friction among the pieces of the ore. When the washing is finished, a door in one of the sides of the trough is opened, and the current removes the ore into a more spacious basin, where it is subjected to a kind of picking. It is frequently indeed passed through sieves in different modes. See LEAD and TIN, for figures of buddles and dollies.

III. Stamping. Before describing the refined methods of washing the more valuable ores of copper, silver, lead, &c., it is proper to point out the means of reducing them into a powder of greater or less fineness, by stamping, so called from the name stamps of the pestles employed for that purpose. Its usefulness is not restricted to preparing the ores; for it is employed in almost every smelting house for pounding clays, charcoal, scoriæ, &c. A stamping mill or pounding machine, fig. 670., consists of several movable pillars of wood l l l, placed vertically, and supported in this position between frames of carpentry K K K. These pieces are each armed at their under end with a mass of iron m. An arbor or axle a a, moved by water, and turning horizontally, tosses up these wooden pestles, by means of wipers or cams, which lay hold of the shoulders of the pestles at l l l. These are raised in succession, and fall into an oblong trough below m m, scooped out in the ground, having its bottom covered either with plates of iron or hard stones. In this trough, beneath these pestles, the ore to be stamped is allowed to fall from a hopper above, which is kept constantly full.

The trough is closed in at the sides by two partitions, and includes three or four pestles; which the French miners call a battery. They are so disposed that their ascent and descent take place at equal intervals of time.

Usually a stamping machine is composed of several batteries (two, three, or four), and the arrangement of the wipers on the arbor of the hydraulic wheel is such that there is constantly a like number of pestles lifted at a time; a circumstance important for maintaining the uniform going of the machine.

The matters that are not to be exposed to subsequent washing are stamped dry, that is without leading water into the trough; and the same thing is sometimes done with the rich ores, whose lighter parts might otherwise be lost.

Most usually, especially for ores of lead, silver, copper, &c., the trough of the stamper is placed in the middle of a current of water, of greater or less force; which, sweeping off the pounded substances, deposits them at a greater or less distance onwards, in the order of the size and richness of the grain; constituting a first washing, as they escape from beneath the pestles.

In the dry stamping, the fineness of the powder depends on the weight of the pestles, the height of their fall, and the period of their action upon the ore; but in the stampers exposed to a stream of water, the retention of the matters in the trough is longer or shorter, according to the facility given for their escape. Sometimes these matters flow out of the chest over its edges, and the height of the line they must surmount has an influence on the size of the grain; at other times, the water and the pounded matter which it carries off, are made to pass through a grating, causing a kind of sifting at the same time. There are, however, some differences in the results of these two methods. Lastly, the quantity of water that traverses the trough, as well as its velocity, has an influence on the discharge of the pounded matters, and consequently on the products of the stampers.

The size of the particles of the pounded ore being different, according to the variable hardness of the matters which compose them, suggests the means of classing them, and distributing them nearly in the order of their size and specific gravity, by making the water, as it escapes from the stamping trough, circulate in a system of canals called a labyrinth, where it deposits successively, in proportion as it loses its velocity, the earthy and metallic matters it had floated along. These metalliferous portions, especially when they have a great specific gravity like galena, would be deposited in the first passages, were it not that from their hardness being inferior to that of the gangue, they are reduced to a much finer powder, or into thin plates, which seem to adhere to both the watery and earthy particles; whence they have to be sought for among the finest portions of the pulverised gangue, called slime, schlich, or schlamme.

There are several methods of conducting the stamps; in reference to the size of the grains wished to be obtained, and which is previously determined agreeably to the nature of the ore, and of the gangue; its richness, &c. The height of the slit that lets the pounded matters escape, or the diameters of the holes in the grating, their distance, the quantity of water flowing in, its velocity, &c., modify the result of the stamping operation.

When it is requisite to obtain powder of an extreme fineness, as for ores that are to be subjected to the process of amalgamation, they are passed under millstones, as in common corn mills; and after grinding, they are bolted so as to form a species of flour; or they are crushed between rolls. See LEAD and TIN.

Washing of ores.

IV. The ores pounded under the stamps are next exposed to very delicate operations, both tedious and costly, which are called the washings. Their purpose is to separate mechanically the earthy matters from the metallic portion, which must therefore have a much higher specific gravity; for otherwise, the washing would be impracticable.

The medium employed to diminish the difference of specific gravity, and to move along the lightest matters, is water; which is made to flow with greater or less velocity and abundance over the schlich or pasty mud spread on a table of various inclination.

But as this operation always occasions, not only considerable expense, but a certain loss of metal, it is right to calculate what is the degree of richness below which washing is unprofitable; and on the other hand, what is the degree of purification of the schlich at which it is proper to stop, because too much metal would be lost comparatively with the expense of fusing a small additional quantity of gangue. There cannot, indeed, be any fixed rule in this respect, since the elements of these calculations vary for every work.

Before describing the different modes of washing, we must treat of the sifting or riddling, whose purpose, like that of the labyrinth succeeding the stamps, is to distribute and to separate the ores (which have not passed through the water stamps) in the order of the coarseness of grain. This operation is practised particularly upon the debris of the mine, and the rubbish produced in breaking the ores. These substances are put into a riddle, or species of round or square sieve, whose bottom is formed of a grating instead of a plate of metal pierced with holes. This riddle is plunged suddenly and repeatedly into a tub or cistern filled with water. This liquid enters through the bottom, raises up the mineral particles, separates them and keeps them suspended for an instant, after which they fall down in nearly the order of their specific gravities, and are thus classed with a certain degree of regularity. The sieve is sometimes dipped by the immediate effort of the washer; sometimes it is suspended to a swing which the workman moves; in order that the riddling may be rightly done, the sieve should receive but a single movement from below upwards; in this case the ore is separated from the gangue, and if there be different specific gravities, there is formed in the sieve as many distinct strata, which the workman can easily take out with a spatula, throwing the upper part away when it is too poor to be re-sifted. This operation by the hand-sieve, is called riddling in the tub, or riddling by deposit.

We may observe, that during the sifting, the particles which can pass across the holes of the bottom, fall into the tub and settle down there; whence they are afterwards gathered out, and exposed to washing when they are worth the trouble.

Sometimes, as at Poullaouen, the sieves are conical, and held by means of two handles by a workman; and instead of receiving a single movement, as in the preceding method, the sifter himself gives them a variety of dexterous movements in succession. His object is to separate the poor portions of the ore from the richer; in order to subject the former to the stamp mill.

Among the siftings and washings which ores are made to undergo, we must notice among the most useful and ingenious, those practised by iron gratings, called on the Continent grilles anglaises, and the step-washings of Hungary, laveries à gradins. These methods of freeing the ores from the pulverulent earthy matters, consist in placing them, at their out-put from the mine, upon gratings, and bringing over them a stream of water, which merely takes down through the bars the small fragments, but carries off the pulverulent portions. The latter are received in cisterns, where they are allowed to rest long enough to settle to the bottom. The washing by steps is an extension of the preceding plan. To form an idea, let us imagine a series of grates placed successively at different levels, so that the water, arriving on the highest, where the ore for washing lies, carries off a portion of it, through this first grate upon a second closer in its bars, thence to a third, &c., and finally into labyrinths or cisterns of deposition.

The grilles anglaises are similar to the sleeping tables used at Idria. The system of these en gradins is represented in fig. 671. There are 5 such systems in the works at Idria, for the sorting of the small morsels of quicksilver ore, intended for the stamping mill. These fragments are but moderately rich in metal, and are picked up at random, of various sizes, from that of the fist to a grain of dust.

These ores are placed in the chest a, below the level of which 7 grates are distributed, so that the fragments which pass through the first b, proceed by an inclined conduit on to the second grate c, and so in succession. (See the conduits l, o, p). In front, and on a level with each of the grates b, c, d, &c., a child is stationed on one of the floors, 1, 2, 3, to 7.

A current of water, which falls into the chest a, carries the fragments of ore upon the grates. The pieces which remain upon the two grates b and c, are thrown on the adjoining table v, where they undergo a sorting by hand; there the pieces are classified, 1. into gangue to be thrown away; 2. into ore for the stamp mill; 3. into ore to be sent directly to the furnace. The pieces which remain on each of the succeeding grates, d, e, f, g, h, are deposited on those of the floors 3 to 7, in front of each. Before every one of these shelves a deposit-sieve is established, (see t, u,) and the workmen in charge of it stand in one of the corresponding boxes, marked 8 to 12. The sieve is represented only in front of the chest h, for the sake of clearness.

Each of the workmen placed in 8, 9, 10, 11, 12, operates on the heap before him; the upper layer of the deposit formed in his sieve, is sent to the stamping house, and the inferior layer directly to the furnace.

As to the grains which, after traversing the five grates, have arrived at the chest x, they are washed in the two chests y, which are analogous to the German chests to be presently described. The upper layer of what is deposited in y is sent to the furnace; the rest is treated anew on three tables of percussion, similar to the English brake-sieves, also to be presently described.

After several successive manipulations on these tables, an upper stratum of schlich is obtained fit for the furnace; an intermediate stratum, which is washed anew by the same process; and an inferior stratum, that is sent to the system of stamps, fig. 672.

This figure represents the general ground plan of a stamping and washing mill. The stamps F are composed of two batteries similar to fig. 670. The ore passes in succession under three pestles of cast iron, each of which is heavier the nearer it is to the sieve through which the sand or pounded matter escapes.

In the upper part of the figure we see issuing from the stamps, two conduits destined to receive the water and the metalliferous sand with which it is loaded. The first, marked F, S, w, is used only when a certain quality of ore is stamped, richer in metal than is usually treated by means of the second conduit, the first being closed. The second conduit, or that employed for ordinary manipulation when the other is shut, is indicated by F, 0·7, B; then by 0·58 and 0·29. These numbers express the depth of the corresponding portions of this conduit. From F to B, the conduit or water-course is divided into three portions much shallower, called the rich conduit, the middle conduit, and the inferior. Beyond the basin B, the conduit takes the name of labyrinth. There the muddy sediments of ore are deposited; being the finer the further they are from the stamps F. Darts indicate the direction of the stream in the labyrinth. On the German chests, placed at 3, the sand derived from the rich and middle conduits is treated, in order to obtain three distinct qualities of schlich, as already mentioned. P is a cloth-covered table, for treating the deposit of the German chests at 3. M N are two sweep tables (à balai), for treating the ore collected in the lower conduit, which precedes the midmost of the three German chests. Upon the three similar tables R T V, are treated in like manner the muddy deposits of the labyrinth, which forms suite to three parallel German chests situated at 3, not shown for want of room in the figure, but connected in three rectangular zigzags with each other, as well as by a transverse branch to the points 0·7 and P. At the upper part of these five sweep tables, the materials which are to undergo washing are agitated in two boxes O O, by small paddle-wheels.

We shall now describe the percussion-tables used in the Hartz, for treating the sand of ore obtained from the conduits represented above.

Figs. 673, 674. and 675. exhibit a plan, a vertical section, and elevation, of one of these tables, taken in the direction of its length. The arbor or great shaft in prolongation from the stamps mill, is shown in section perpendicularly to its axis, at A. The cams or wipers are shown round its circumference, one of them having just acted on n.

These cams, by the revolution of the arbor, cause the alternating movements of a horizontal bar of wood o, u, which strikes at the point u against a table d, b, c, u. This table is suspended by two chains t, at its superior end, and by two rods at its lower end. After having been pushed by the piece o, u, it rebounds to strike against a block or bracket B. A lever p, q, serves to adjust the inclination of the movable table, the pivots q being points of suspension.

The ore-sand to be washed, is placed in the chest a, into which a current of water runs. The ore floated onwards by the water, is carried through a sieve on a sloping small table x, under which is concealed the higher end of the movable table d, b, c, u; and it thence falls on this table, diffusing itself uniformly over its surface. The particles deposited on this table form an oblong talus (slope) upon it; the successive percussions that it receives, determine the weightier matters, and consequently those richest in metal, to accumulate towards its upper end at u. Now the workman by means of the lever p, raises the lower end d a little in order to preserve the same degree of inclination to the surface on which the deposit is strewed. According as the substances are swept along by the water, he is careful to remove them from the middle of the table towards the top, by means of a wooden roller. With this intent, he walks on the table d b c u, where the sandy sediment has sufficient consistence to bear him. When the table is abundantly charged with the washed ore, the deposit is divided into three bands or segments d b, b c, c u. Each of these bands is removed separately and thrown into the particular heap assigned to it. Every one of the heaps thus formed becomes afterwards the object of a separate manipulation on a percussion table, but always according to the same procedure. It is sufficient in general to pass twice over this table the matters contained in the heap, proceeding from the superior band c u, in order to obtain a pure schlich; but the heap preceding from the intermediate belt b c, requires always a greater number of manipulations, and the lower band d b still more. These successive manipulations are so associated that eventually each heap furnishes pure schlich, which is obtained from the superior band c u. As to the lightest particles which the water sweeps away beyond the lower end of the percussion table, they fall into conduits; whence they are lifted to undergo a new manipulation.

Fig. 676. is a profile of a plan which has been advantageously substituted, in the Hartz, for that part of the preceding apparatus which causes the jolt of the piece o u against the table d b c u. By means of this plan, it is easy to vary, according to the circumstances of a manipulation always delicate, the force of percussion which a bar x y, ought to communicate by its extremity y. With this view, a slender piece of wood u is made to slide in an upright piece, v x, adjusted upon an axis at v. To the piece u a rod of iron is connected, by means of a hinge z; this rod is capable of entering more or less into a case or sheath in the middle of the piece v x, and of being stopped at the proper point, by a thumb-screw which presses against this piece. If it be wished to increase the force of percussion, we must lower the point z; if to diminish it, we must raise it. In the first case, the extremity of the piece u, advances so much further under the cam of the driving shaft t; in the second, it goes so much less forwards; whereby the adjustment is produced.

Figs. 677. and 678. represent a complete system of sleeping tables, tables dormantes; such as are mounted in Idria. Fig. 678. is the plan, and fig. 677. a vertical section. The mercurial ores, reduced to a sand by stamps like those of fig. 672., pass into a series of conduits a a, b b, c c, which form three successive floors below the level of the floor of the works. The sand taken out of these conduits is thrown into the cells q; whence they are transferred into the trough e, and water is run upon them by turning two stopcocks for each trough. The sand thus diffused upon each table, runs off with the water by a groove f, comes upon a sieve h, spreads itself upon the board g, and thence falls into the slanting chest, or sleeping table i k. The under surface k of this chest is pierced with holes, which may be stopped at pleasure with wooden plugs. There is a conduit m, at the lower end of each table, to catch the light particles carried off by the water out of the chest i k, through the holes properly opened, while the denser parts are deposited upon the bottom of this chest. A general conduit n passes across at the foot of all the chests i k; it receives the refuse of the washing operations.

Fig. 679. is a set of stamping and washing works for the ores of argentiferous galena, as mounted at Bockwiese, in the district of Zellerfeldt, in the Hartz.

A is the stamp mill and its subsidiary parts; among which are a, the driving or main shaft; b, the overshot water-wheel; c c, six strong rings or hoops of cast iron, for receiving each a cam or tappet; g, the brake of the machine; k, k, k, the three standards of the stamps; l l, &c. six pestles of pine wood, shod with lumps of cast iron. There are two chests, out of which the ore to be ground falls spontaneously into the two troughs of the stamps. Of late years, however, the ore is mostly supplied by hand; the watercourse terminates a short distance above the middle of the wheel b. There is a stream of water for the service of the stamps, and conduits proceeding from it, to lead the water into the two stamp troughs; the conduit of discharge is common to the two batteries or sets of stamps through which the water carries off the sand or stamped ore. There is a movable table of separation, mounted with two sieves. The sands pass immediately into the conduit placed upon a level with the floor, and separated into two compartments, the first of which empties its water into the second. There are two boards of separation, or tables, laid upon the ground, with a very slight slope of only 15 inches from their top to their bottom. Each of these boards is divided into four cases with edges; the whole being arranged so that it is possible, by means of a flood-gate or sluice, to cause the superfluous water of the case to pass into the following ones. Thus the work can go on without interruption, and alternately upon the two boards. There are winding canals in the labyrinth, N, N, N, in which are deposited the particles carried along by the water which has passed upon the boards. The depth of these canals gradually increases from 12 to 20 inches, to give a suitable descent for maintaining the water-flow. At D, two percussion tables are placed. F G are two German chests. H J are two percussion tables, which are driven by the cams z z, fixed upon the main shaft x y. K K´ are two sloping sweep tables (à balai).

The German chests are rectangular, being about 3 yards long, half a yard broad, with edges half a yard high; and their inclination is such that the lower end is about 15 inches beneath the level of the upper. At their upper end, usually called the bolster, a kind of trough or box, without any edge at the side next the chest, is placed, containing the ore to be washed. The water is allowed to fall upon the bolster in a thin sheet.

The sleeping tables have upright edges; they are from 4 to 5 yards long, nearly 2 yards wide, and have fully a yard of inclination.

The preceding tables are sometimes covered with cloth, particularly in treating ores that contain gold, on a supposition that the woollen or linen fibres would retain more surely the metallic particles; but this method appears on trial to merit no confidence, for it produces a very impure schlich.

Fig. 680. is a swing-sieve employed in the Hartz, for sifting the small fragments of the ore of argentiferous lead. Such an apparatus is usually set up in the outside of a stamp, and washing mill; its place being denoted by the letter A, fig. 672. The two movable chests or boxes A B, of the sieve, are connected together, at their lower ends, with an upright rod, which terminates at one of the arms of a small balance beam, mounted between the driving shaft of the stamps and the sieve, perpendicularly to the length of both. The opposite arm of this beam carries another upright rod, which ears (cams or mentonnets), placed on purpose upon the driving shaft, may push down. During this movement the two lower ends A, B, are raised; and when the peg-cam of the shaft quits the rod which it had depressed, the swing chests fall by their own weight. Thus they are made to vibrate alternately upon their axes. The small ore is put into the upper part of the chest A, over which a stream of water falls from an adjoining conduit. The fragments which cannot pass through a cast-iron grid in the bottom of that chest, are sorted by hand upon a table in front of A, and they are classed by the workman, either among the ores to be stamped, whether dry or wet, or among the rubbish to be thrown away, or among the copper ores to be smelted by themselves. As to the small particles which fall through the grid upon the chest B, supplied also with a stream of water, they descend successively upon two other brass wire sieves, and also through the iron wire r, in the bottom of B.

In certain mines of the Hartz, tables called à balais, or sweeping tables, are employed. The whole of the process consists in letting flow, over the sloping table, in successive currents, water charged with the ore, which is deposited at a less or greater distance, as also pure water for the purpose of washing the deposited ore, afterwards carried off by means of this sweeping operation.

At the upper end of these sweep-tables, the matters for washing are agitated in a chest, by a small wheel with vanes, or flap-boards. The conduit of the muddy waters opens above a little table or shelf; the conduit of pure water, which adjoins the preceding, opens below it. At the lower part of each of these tables, there is a transverse slit, covered by a small door with hinges, opening outwardly, by falling back towards the foot of the table. The water spreading over the table, may at pleasure be let into this slit, by raising a bit of leather which is nailed to the table, so as to cover the small door when it is in the shut position; but when this is opened, the piece of leather then hangs down into it. Otherwise the water may be allowed to pass freely above the leather, when the door is shut. The same thing may be done with a similar opening placed above the conduit. By means of these two slits, two distinct qualities of schlich may be obtained, which are deposited into two distinct conduits or canals. The refuse of the operation is turned into another conduit, and afterwards into ulterior reservoirs, whence it is lifted out to undergo a new washing.

In the percussion tables, the water for washing the ores is sometimes spread in slender streamlets, sometimes in a full body, so as to let two cubic feet escape per minute. The number of shocks communicated per minute, varies from 15 to 36; and the table may be pushed out of its settled position at one time, three quarters of an inch, at another nearly 8 inches. The coarse ore-sand requires in general less water, and less slope of table, than the fine and pasty sand.

The mechanical operations which ores undergo, take place commonly at their out-put from the mine, and without any intermediate operation. Sometimes, however, the hardness of certain gangues (vein-stones), and of certain iron-ores, is diminished by subjecting them to calcination previously to the breaking and stamping processes.

When it is intended to wash certain ores, an operation founded on the difference of their specific gravities, it may happen that by slightly changing the chemical state of the substances that compose the ore, the earthy parts may become more easily separable, as also the other foreign matters. With this view, the ores of tin are subjected to a roasting, which by separating the arsenic, and oxidizing the copper which are intermixed, furnishes the means of obtaining, by the subsequent washing, an oxide of tin much purer than could be otherwise procured. In general, however, these are rare cases; so that the washing almost always immediately succeeds the picking and stamping; and the roasting comes next, when it needs to be employed.

The operation of roasting is in general executed by various processes, relatively to the nature of the ores, the quality of the fuel, and to the object in view. The greatest economy ought to be studied in the fuel, as well as the labour; two most important circumstances, on account of the great masses operated upon.

Three principal methods may be distinguished; 1. the roasting in a heap in the open air, the most simple of the whole; 2. the roasting executed between little walls, and which may be called case-roasting (rost-stadeln, in German); and 3. roasting in furnaces.

We may remark, as to the description about to be given of these different processes, that in the first two, the fuel is always in immediate contact with the ore to be roasted, whilst in furnaces, this contact may or may not take place.

1. The roasting in the open air, and in heaps more or less considerable, is practised upon iron ores, and such as are pyritous or bituminous. The operation consists in general in spreading over a plane area, often bottomed with beaten clay, billets of wood arranged like the bars of a gridiron, and sometimes laid crosswise over one another, so as to form a uniform flat bed. Sometimes wood charcoal is scattered in, so as to fill up the interstices, and to prevent the ore from falling between the other pieces of the fuel. Coal is also employed in moderately small lumps; and even occasionally, turf. The ore either simply broken into pieces, or even sometimes under the form of schlich, is piled up over the fuel; most usually alternate beds of fuel and ore are formed.

The fire, kindled in general at the lower part, but sometimes, however, at the middle chimney, spreads from spot to spot, putting the operation in train. The combustion must be so conducted as to be slow and suffocated, to prolong the ustulation, and let the whole mass be equably penetrated with heat. The means employed to direct the fire, are to cover outwardly with earth the portions where too much activity is displayed, and to pierce with holes or to give air to those where it is imperfectly developed. Rains, winds, variable seasons, and especially good primary arrangements of a calcination, have much influence on this process, which requires, besides, an almost incessant inspection at the beginning.

Nothing in general can be said as to the consumption of fuel, because it varies with its quality, as well as with the ores and the purpose in view. But it may be laid down as a good rule, to employ no more fuel than is strictly necessary for the kind of calcination in hand, and for supporting the combustion; for an excess of fuel would produce, besides an expense uselessly incurred, the inconvenience, at times very serious, of such a heat as may melt or vitrify the ores; a result entirely the reverse of a well-conducted ustulation.

Figs. 681, 682, 683. represent the roasting in mounds, as practised near Goslar in the Hartz, and at Chessy in the department of the Rhone. Fig. 681. is a vertical section in the line h c of figs. 682. and 683. In fig. 682. there is shown in plan, only a little more than one half of the quadrangular truncated pyramid, which constitutes the heap. Fig. 683. shows a little more than one fourth of a bed of wood, arranged at the bottom of the pyramid, as shown by a a, fig. 681., and c g h, fig. 683. C is a wooden chimney, formed within the heap of ore, at whose bottom c there is a little parcel of charcoal, d d are large lumps of ore distributed upon the wooden pile a a; e e are smaller fragments, to cover the larger; f f is rubbish and clay laid smoothly in a slope over the whole. g, fig. 683., a passage for air left under the bed of billets; of which there is a similar one in each of the four sides of the base a a, so that two principal currents of air cross under the upright axis C c, of the truncated pyramid indicated in fig. 681.

The kindling is thrown in by the chimney C. The charcoal c, and the wood a a, take fire; the sulphureous ores d e f are heated to such a high temperature as to vaporize the sulphur. In the Lower Hartz, a heap of this kind continues roasting during four months.

2. The second method. The difficulty of managing the fire in the roasting of substances containing little sulphur, with the greater difficulty of arranging and supporting in their place the schlichs to be roasted, and last of all, the necessity of giving successive fires to the same ores, or to inconsiderable quantities at a time, have led to the contrivance of surrounding the area on which the roasting takes place with three little walls, or with four, leaving a door in the one in front. This is what is called a walled area, and sometimes, improperly enough, a roasting furnace. Inside of these little walls, about 3 feet high, there are often vertical conduits or chimneys made to correspond with an opening on the ground level, in order to excite a draught of air in the adjacent parts. When the roasting is once set agoing, these chimneys can be opened or shut at their upper ends, according to the necessities of the process.

Several such furnaces are usually erected in connexion with each other by their lateral walls, and all terminated by a common wall, which forms their posterior part; sometimes they are covered with a shed supported partly by the back wall, built sufficiently high for this purpose. These dispositions are suitable for the roasting of schlichs, and in general of all matters which are to have several fires; a circumstance often indispensable to a due separation of the sulphur, arsenic, &c.

3. The furnaces employed for roasting the ores and the mattes differ much, according to the nature of the ores, and the size of the lumps. We shall content ourselves with referring to the principal forms.

When iron ores are to be roasted, which require but a simple calcination to disengage the combined water and carbonic acid, egg-shaped furnaces, similar to those in which limestone is burned in contact with fuel, may be conveniently employed; and they present the advantage of an operation which is continuous with a never-cooling apparatus. The analogy in the effects to be produced is so perfect, that the same furnace may be used for either object. Greater dimensions may, however, be given to those destined for the calcination of iron ores. But it must be remembered that this process is applicable only to ores broken into lumps, and not to ores in grains or powder.

It has been attempted to employ the same method a little modified, for the roasting of ores of sulphuret of copper and pyrites, with the view of extracting a part of the sulphur. More or less success has ensued, but without ever surmounting all the obstacles arising from the great fusibility of the sulphuret of iron. For sometimes it runs into one mass, or at least into lumps agglutinated together in certain parts of the furnace, and the operation is either stopped altogether, or becomes more or less languid; the air not being able to penetrate into all the parts, the roasting becomes consequently imperfect. This inconvenience is even more serious than might at first sight appear; for, as the ill-roasted ores now contain too little sulphur to support their combustion, and as they sometimes fall into small fragments in the cooling, they cannot be passed again through the same furnace, and it becomes necessary to finish the roasting in a reverberatory hearth, which is much more expensive.

In the Pyrenees, the roasting of iron ores is executed in a circular furnace, so disposed that the fuel is contained and burned in a kind of interior oven, above which lie the pieces of ore to be calcined. Sometimes the vault of this oven which sustains the ore, is formed of bricks, leaving between them openings for the passage of the flame and the smoke, and the apparatus then resembles certain pottery kilns; at other times the vault is formed of large lumps of ore, carefully arranged as to the intervals requisite to be left for draught over the arch. The broken ore is then distributed above this arch, care being taken to place the larger pieces undermost. This process is simple in the construction of the furnace, and economical, as branches of trees, without value in the forests, may be employed in the roasting. See Lime-kiln figures.

In some other countries, the ores are roasted in furnaces very like those in which porcelain is baked; that is to say, the fuel is placed exteriorly to the body of the furnace in a kind of brick shafts, and the flame traverses the broken ore with which the furnace is filled. In such an apparatus the calcination is continuous.

When it is proposed to extract the sulphur from the iron pyrites, or from pyritous minerals, different furnaces may be employed, among which that used in Hungary deserves notice. It is a rectangular parallelopiped of four walls, each of them being perforated with holes and vertical conduits which lead into chambers of condensation, where the sulphur is collected. The ore placed between the four walls on billets of wood arranged as in figs. 681, 682, 683., for the great roastings in the open air, is calcined with the disengagement of much sulphur, which finds more facility in escaping by the lateral conduits in the walls, than up through the whole mass, or across the upper surface covered over with earth; whence it passes into the chambers of condensation. In this way upwards of a thousand tons of pyrites may be roasted at once, and a large quantity of sulphur obtained. See COPPER.

Roasting of Pyrites.--Figs. 684, 685. represent a furnace which has been long employed at Fahlun in Sweden, and several other parts of that kingdom, for roasting iron pyrites in order to obtain sulphur. This apparatus was constructed by the celebrated Gahn. Fig. 684. is a vertical section, in the line k d n o of fig. 685., which is a plan of the furnace; the top being supposed to be taken off. In both figures the conduit may be imagined to to be broken off at e; its entire length in a straight line is 43 feet beyond the dotted line e n, before the bend, which is an extension of this conduit. Upon the slope a b of a hillock a b c, lumps r of iron pyrites are piled upon the pieces of wood i i for roasting. A conduit d f e forms the continuation of the space denoted by r, which is covered by stone slabs so far as f; and from this point to the chamber h it is constructed in boards. At the beginning of this conduit, there is a recipient g. The chamber h is divided into five chambers by horizontal partitions, which permit the circulation of the vapours from one compartment to another. The ores r being distributed upon the billets of wood i i, whenever these are fairly kindled, they are covered with small ore, and then with rammed earth l l. Towards the point m, for a space of a foot square, the ores are covered with movable stone slabs, by means of which the fire may be regulated, by the displacement of one or more, as may be deemed necessary. The liquid sulphur runs into the recipient g, whence it is laded out from time to time. The sublimed sulphur passes into the conduit f e and the chamber h, from which it is taken out, and washed with water, to free it from sulphuric acid with which it is somewhat impregnated; it is afterwards distilled in cast-iron retorts. The residuum of the pyrites is turned to account in Sweden, for the preparation of a common red colour much used as a pigment for wooden buildings.

The reverberatory furnace affords one of the best means of ustulation, where it is requisite to employ the simultaneous action of heat and atmospherical air to destroy certain combinations, and to decompose the sulphurets, arseniurets, &c. It is likewise evident that the facility thus offered of stirring the matters spread out on the sole, in order to renew the surfaces, of observing their appearances, of augmenting or diminishing the degree of heat, &c., promise a success much surer, a roasting far better executed, than by any other process. It is known, besides, that flame mingled with much undecomposed air issuing from the furnace, is highly oxidizing, and is very fit for burning away the sulphur, and oxidizing the metals. Finally, this is almost the only method of rightly roasting ores which are in a very fine powder. If it be not employed constantly and for every kind of ore, it is just because more economy is found in practising calcination in heaps, or on areas enclosed by walls; besides, in certain mines, a very great number of these furnaces, and many workmen, would be required to roast the considerable body of ores that must be daily smelted. Hence there would result from the construction of such apparatus and its maintenance a very notable outlay, which is saved in the other processes.

But in every case where it is desired to have a very perfect roasting, as for blende from which zinc is to be extracted, for sulphuret of antimony, &c., or even for ores reduced to a very fine powder, and destined for amalgamation, it is proper to perform the operation in a reverberatory furnace. When very fusible sulphurous ores are treated, the workman charged with the calcination must employ much care and experience, chiefly in the management of the fire. It will sometimes, indeed, happen, that the ore partially fuses; when it becomes necessary to withdraw the materials from the furnace, to let them cool and grind them anew, in order to recommence the operation. The construction of these furnaces demands no other attention than to give to the sole or laboratory the suitable size, and so to proportion to this the grate and the chimney that the heating may be effected with the greatest economy.

The reverberatory furnace is always employed to roast the ores of precious metals, and especially those for amalgamation; as the latter often contain arsenic, antimony, and other volatile substances, they must be disposed of in a peculiar manner.

The sole, usually very spacious, is divided into two parts, of which the one farthest off from the furnace is a little higher than the other. Above the vault there is a space or chamber in which the ore is deposited, and which communicates with the laboratory by a vertical passage; which serves to allow the ore to be pushed down, when it is dried and a little heated. The flame and the smoke which escape from the sole or laboratory pass into condensing chambers, before entering into the chimney of draught, so as to deposit in them the oxide of arsenic and other substances. When the ore on the part of the sole farthest from the grate has suffered so much heat as to begin to be roasted, has became less fusible, and when the roasting of that in the nearer part of the sole is completed, the former is raked towards the fire-bridge, and its ustulation is finished by stirring it over frequently with a paddle, skilfully worked, through one of the doors left in the side for this purpose. The operation is considered to be finished when the vapours and the smell have almost wholly ceased; its duration depending obviously on the nature of the ores.

When this furnace is employed to roast very arsenical ores, as the tin ores of Schlackenwald in Bohemia, and at Ehrenfriedersdorf in Saxony, the arsenical pyrites of Geyer (in Saxony), &c., the chambers of condensation for the arsenious acid are much more extensive than in the furnaces commonly used for roasting galena, copper, or even silver ores.

Figs. 686, 687, 688. represent a reverberatory furnace employed in the smelting works of Lautenthal, in the Hartz, for roasting the schlichs of lead ores, which contain much blende or sulphuret of zinc. In fig. 686. we see that the two parts A B, B C, are absolutely like, the two furnaces being built in one body of brickwork. Fig. 687. is the plan of the furnace B C, taken at the level E F of fig. 686. Fig. 688. is a vertical section of the similar furnace A B, taken in the prolongation of the line G H in fig. 687.

a is the fire-place of the furnace, its grate and ash-pit. b is the conduit of vaporization, which communicates with the chambers c; c, chambers into which the vaporized substances are deposited; d, chimney for the escape of the smoke of the fire-place a, after it has gone through the space b c c; e´, is the charging door, with a hook hanging in front to rest the long iron rake upon, with which the materials are turned over; f, chamber containing a quantity of schlich destined for roasting; this chamber communicates with the vaulted corridor (gallery) D, seen in fig. 686.; g, orifice through which the schlich is thrown into the furnace; h, area or hearth of the reverberatory furnace, of which the roof is certainly much too high; i, channels for the escape of the watery vapours; k l, front arcade, between which and the furnace, properly speaking, are the two orifices of the conduits, which terminate at the channels m, m´. m is the channel for carrying towards the chimney d, the vapours which escape by the door e´. n is a walled-up door, which is opened from time to time, to take out of the chambers c, c, the substances that may be deposited in them.

At the smelting works of Lautenthal, in such a roasting furnace, from 6 to 9 quintals (cwts.) of schlich are treated at a time, and it is stirred frequently with an iron rake upon the altar h. The period of this operation is from 6 to 12 hours, according as the schlich may be more or less dry, more or less rich in lead, or more or less charged with blende. When the latter substance is abundant, the process requires 12 hours, with about 60 cubic feet of cleft billets for fuel.

In such furnaces are roasted the cobalt ores of Schneeberg in Saxony, the tin ores of Schlackenwald in Bohemia, of Ehrenfriedersdorf in Saxony, and elsewhere; as also the arsenical pyrites at Geyer in Saxony. But there are poison towers and extensive condensing chambers attached in the latter case. See ARSENIC.

Figs. 689, 690, 691. represent the reverberatory furnace generally employed in the Hartz, in the district of Mansfeldt, Saxony, Hungary, &c., for the treatment of black copper, and for refining rose copper upon the great scale. An analogous furnace is used at Andreasberg for the liquefaction or purification of the mattes, and for workable lead when it is much loaded with arsenic.

Fig. 689. presents the elevation of the furnace parallel to the line I K, of the plan fig. 690.; which plan is taken at the level of the tuyère n, of fig. 691.; fig. 691. is a vertical section in the line L M, fig. 690. k represents one of two basins of reception, brasqued with clay and charcoal; n, n, two tuyères, through which enters the blast of two pairs of bellows, like those shown at Cupellation of SILVER; q, door by which the matter to be melted is laid upon the sole of the furnace; v, v, two points where the sole is perforated, when necessary to run off the melted matter into either of the basins h; x, door through which the slags or cinders floating upon the surface of the melted metal are raked out; y, door of the fire-place. The fuel is laid upon a grate above an ash-pit, and below the arch of a reverberatory which is contiguous to the dome or cap of the furnace properly so called. In the section, fig. 691., the following parts may be noted: 1, 2, 3, mason-work of the foundation; 4, vapour channels or conduits, for the escape of the humidity; 5, bed of clay; 6, brasque composed of clay and charcoal, which forms the concavity of the hearth.

Figs. 692, 693, 694., show the furnace employed for liquation in one of the principal smelting works of the Hartz. Fig. 694. exhibits the working area charged with the liquation cakes and charcoal, supported by sheets of wrought iron; being an image of the process in action. Fig. 693. is the plan, in the line F, G, of fig. 692.

A liquation cake is composed of--

Black copper holding at least 5 or 6 loths (2-1/2 or 3 oz.) of silver per cwt., and weighing 90 to 96 lbs.

Lead obtained from litharge, 2 cwts. Litharge, 1/2 cwt.

From 30 to 32 cakes are successively worked in one operation, which lasts about 5 hours; the furnace is brought into action, as usual, with the aid of slags; then a little litharge is added; when the lead begins to flow, the copper is introduced, and when the copper flows, lead is added, so that the mixture of the metals may be effected in the best way possible.

From 8 to 16 of these cakes (pains) are usually placed in the liquation furnace, figs. 692, 693, 694. The operation lasts 3 or 4 hours, in which time about 1-1/2 quintals of charcoal are consumed. The cakes are covered with burning charcoal, supported, as I have said, by the iron plates. The workable lead obtained flows off towards the basin in front of the furnace; whence it is laded out into moulds set alongside. See fig. 693. If the lead thus obtained be not sufficiently rich in silver to be worth cupellation, it is employed to form new liquation cakes. When it contains from 5 to 6 loths of silver per cwt., it is submitted to cupellation in the said smelting works. See SILVER.

The trompe, or water-blowing engine, figs. 695, 696, 697. Fig. 695. is the elevation; fig. 696. is a vertical section, made at right angles to the elevation. The machine is formed of two cylindrical pipes, the bodies of the trompe b b, set upright, called the funnels, which terminate above in a water cistern a, and below in a close basin under c, called the tub or drum. The conical part p, of the funnel has been called etranguillon, being strangled, as it were, in order that the water discharged into the body of the trompe shall not fill the pipe in falling, but be divided into many streamlets. Below this narrow part, eight holes, q q, are perforated obliquely through the substance of the trompe, called the vent-holes or nostrils, for admitting the air, which the water carries with it in its descent. The air afterwards parts from the water, by dashing upon a cast-iron slab, placed in the drum upon the pedestal d. An aperture l, at the bottom of the drum, allows the water to flow away after its fall; but, to prevent the air from escaping along with it, the water as it issues is received in a chest l m o n, divided into two parts by a vertical slide-plate between m n. By raising or lowering this plate, the water may be maintained at any desired level within the drum, so as to give the included air any determinate degree of pressure. The superfluous water then flows off by the hole o.

The air-pipe e f, fig. 696., is fitted to the upper part of the drum; it is divided, at the point f, into three tubes, of which the principal one is destined for the furnace of cupellation, whilst the other two g g, serve for different melting furnaces. Each of these tubes ends in a leather pocket, and an iron nose-pipe k, adjusted in the tuyère of the furnace. At Pesey, and in the whole of Savoy, a floodgate is fitted into the upper cistern a, to regulate the admission of water into the trome; but in Carniola, the funnel p is closed with a wooden plug, suspended to a cord, which goes round a pulley mounted upon a horizontal axis, as shewn in fig. 697. By the plug a being raised more or less, merely the quantity of water required for the operation is admitted. The plug is pierced lengthwise with an oblique hole c c, in which the small tube c is inserted, with its top some way above the water level, through which air may be admitted into the heart of the column descending into the trompe p q.

The ordinary height of the trompe apparatus is about 26 or 27 feet to the upper level of the water cistern; its total length is 11 mètres (36 feet 6 inches), and its width 2 feet, to give room for the drums. It is situated 10 mètres (33-1/3 feet) from the melting furnace. This is the case at the smelting works of Jauerberg, in Upper Carniola.

OF THE ASSAY OF ORES.

Assays ought to occupy an important place in metallurgic instructions, and there is reason to believe that the knowledge of assaying is not sufficiently diffused, since its practice is so often neglected in smelting houses. Not only ought the assays of the ores under treatment, to be frequently repeated, because their nature is subject to vary; but the different products of the furnaces should be subjected to reiterated assays, at the several periods of the operations. When silver or gold ores are in question, the docimastic operations, then indispensable, exercise a salutary controul over the metallurgic processes, and afford a clear indication of the quantities of precious metal which they ought to produce.

By the title Assays, in a metallurgic point of view, is meant the method of ascertaining for any substance whatever, not only the presence and the nature of a metal, but its proportional quantity. Hence the operations which do not lead to a precise determination of the metal in question, are not to be arranged among the assays now under consideration. Experiments made with the blow-pipe, although capable of yielding most useful indications, are like the touchstone in regard to gold, and do not constitute genuine assays.

Three kinds of assays may be practised in different circumstances, and with more or less advantage upon different ores. 1. The mechanical assay; 2. the assay by the dry way; 3. the assay by the humid way.

1. Of mechanical assays.--These kinds of assays consist in the separation of the substances mechanically mixed in the ores, and are performed by a hand-washing, in a small trough of an oblong shape, called a sebilla. After pulverizing with more or less pains the matters to be assayed by this process, a determinate weight of them is put into this wooden bowl with a little water; and by means of certain movements and some precautions, to be learned only by practice, the lightest substances may be pretty exactly separated, namely, the earthy gangues from the denser matter or metallic particles, without losing any sensible portion of them. Thus a schlich of greater or less purity will be obtained, which may afford the means of judging by its quality of the richness of the assayed ores, and which may thereafter be subjected to assays of another kind, whereby the whole metal may be insulated.

Washing, as an assay, is practised on auriferous sands; on all ores from the stamps, and even on schlichs already washed upon the great scale, to appreciate more nicely the degree of purity they have acquired. The ores of tin in which the oxide is often disseminated in much earthy gangue, are well adapted to this species of assay, because the tin oxide is very dense. The mechanical assay may also be employed in reference to the ores whose metallic portion presents an uniform composition, provided it also possesses considerable specific gravity. Thus the ores of sulphuret of lead (galena) being susceptible of becoming almost pure sulphurets (within 1 or 2 per cent.) by mere washing skilfully conducted, the richness of that ore in pure galena, and consequently in lead, may be at once concluded; since 120 of galena contain 104 of lead, and 16 of sulphur. The sulphuret of antimony mingled with its gangue may be subjected to the same mode of assay, and the result will be still more direct, since the crude antimony is brought into the market after being freed from its gangue by a simple fusion.

The assay by washing is also had recourse to for ascertaining if the scoriæ or other products of the furnaces contain some metallic grains which might be extracted from them by stamping and washing on the great scale; a process employed considerably with the scoriæ of tin and copper works.

Of assays by the dry way.--The assay by the dry way has for its object, to show the nature and proportion of the metals contained in a mineral substance. To make a good assay, however, it is indispensably necessary to know what is the metal associated with it, and even within certain limits, the quantity of the foreign bodies. Only one metal is commonly looked after; unless in the case of certain argentiferous ores. The mineralogical examination of the substances under treatment, is most commonly sufficient to afford data in these respects; but the assays may always be varied with different views, before stopping at a definite result; and in every instance, only such assays can be confided in, as have been verified by a double operation.

This mode of assaying requires only a little experience, with a simple apparatus; and is of such a nature as to be practised currently in the smelting works. The air furnace and crucibles employed are described in all good elementary chemical books. These assays are usually performed with the addition of a flux to the ore, or some agent for separating the earthy from the metallic substances; and they possess a peculiar advantage relative to the smelting operations, because they offer many analogies between results on the great scale and experiments on the small. This may even enable us often to deduce, from the manner in which the assay has succeeded with a certain flux, and at a certain degree of heat, valuable indications as to the treatment of the ore in the great way. See FURNACE.

In the smelting houses which purchase the ore, as in Germany, it is necessary to bestow much attention upon the assays, because they serve to regulate the quality and the price of the schlichs to be delivered. These assays are not by any means free from difficulties, especially when ores containing several useful metals are treated, and which are to be dosed or proportioned; ores, for example, including a notable quantity of lead, copper, and silver, mixed together.

In the central works of the Hartz, as well as in those of Saxony, the schlichs as delivered are subjected to docimastic assays, which are verified three times, and by three different persons, one of whom is engaged for the interests of the mining partners, another for that of the smelting house, and a third as arbiter in case of a difference. If the first two results of assaying differ by 1/2 loth (or 1/4 ounce) of silver per cwt. of schlich, the operations must be resumed; but this rarely happens. When out of the three assays, the one differs from the two others by no more than 1/4 loth of silver per cwt., but by more in one, and by less in another, the mean result is adopted. As to the contents of the schlich in lead, the mean results of the assays must be taken. The differences allowed, are three pounds for the schlich, when it contains from 12 to 30 per cent. of lead, increasing to six pounds for schlich, when it contains less than 55 per cent. of that metal.

Assaying forms in great establishments, an important object in reference to time and expense. Thus, in the single work of Franckenscharn, in the Hartz, no less than 300 assays have to be made in a threefold way, every Monday, without taking into account the several assays of the smelting products which take place every Thursday. Formerly fluxes more or less compound were employed for these purposes, and every assay cost about fifteen pence. At present all these assays are made more simply, by much cheaper methods, and cost a penny farthing each upon an average.

Of the assays by the humid way.--The assays by the humid way, not reducible to very simple processes, are true chemical analyses, which may in fact be applied with much advantage, either to ores, or to the products of the furnace; but which cannot be expected to be practised in smelting-houses, on account of the complication of apparatus and reagents they require. Moreover, an expert chemist is necessary to obtain results that can be depended on. The directors of smelting-houses, however, should never neglect any opportunities that may occur of submitting the materials operated upon, as well as their products, to a more thorough examination than the dry way alone can effect. One of the great advantages of similar researches is, to discover and appreciate the minute quantities of injurious substances which impair the malleability of the metals, which give them several bad qualities, about whose nature and cause, more or less error and uncertainty prevail. Chemical analysis, rightly applied to metallurgy, cannot fail to introduce remarkable improvements into the processes.--See the different metals, in their alphabetical places.

For assays in the dry way, both of stony and metallic minerals, the process of Dr. Abich deserves recommendation. In consists in mixing the pulverized mineral with 4 or 6 times its weight of carbonate of baryta in powder, fusing the mixture at a white heat, and then dissolving it after it cools, in dilute muriatic acid. The most refractory minerals, even corundum, cyanite, staurolite, zircon, and felspar, yield readily to this treatment. This process may be employed with advantage upon poor refractory ores. The platinum crucible, into which the mixed materials are put for fusion, should be placed in a Hessian crucible, and surrounded with good coak.

* * * * *

The following tabular view of the metallic produce of the British mines, is given by two very skilful observers, in a work published in 1827, entitled Voyage Metallurgique en Angleterre, par MM. Dufrénoy et Elie de Beaumont:--

Tons. Tons. Tin Cornwall alone 3,160 { Cornwall 9,331 } { Devonshire 537 } { Staffordshire 38 } Copper { Anglesey 738 } { Wales 55 } 11,469 { Cumberland 21 } { Ireland 738 } { Scotland 11 } { Wales 7,500 } { Scotland 2,800 } Lead { Cornwall and Devonshire 800 } 31,900 { Shropshire 800 } { Derbyshire 1,000 } { Cumberland 19,000 } Cast Iron about 600,000[32]

[32] I have converted the weights of lead and cast iron, given in kilogrammes, into tons, at the rate of 1000 kilogrammes per ton; which is sufficiently near.

The manganese raised in England exceeds 2000 tons.

M. Heron de Villefosse inserted in the last number of the Annales des Mines for 1827, the following statistical view of the metallic products of France:--

Tons. Lead in pigs (saumons) 103 Litharge 513 Sulphuret of lead, ground galena (alquifoux) 112 Black copper 164 Antimony 91 Manganese 765 Crude cast iron 25,606 Bar iron 127,643 Steel 3,500 Silver in ingots 1-1/6

The total value of which is estimated at 80 millions of francs; or about 3,400,000 pounds sterling.

METALS; (Metaux, Fr.; Metalle, Germ.) are by far the most numerous class of undecompounded bodies in chemical arrangements. They amount to 41; of which 7 form, with oxygen, bodies possessed of alkaline properties; these are, 1. potassium; 2. sodium; 3. lithium; 4. barytium, or barium; 5. strontium; 6. calcium; 7. magnesium; for even magnesia, the last and feeblest base, tinges turmeric brown, and red cabbage green. The next 5 metals form, with oxygen, the earths proper; they are, 8. yttrium; 9. glucinum; 10. alumium; 11. zirconium; 12. thorinum. The remaining 29 may be enumerated in alphabetical order, as they hardly admit of being grouped into subdivisions with any advantage. They are as follows: 13. antimony; 14. arsenic; 15. bismuth; 16. cadmium; 17. cerium; 18. chromium; 19. cobalt; 20. copper; 21. gold; 22. iridium; 23. iron; 24. lead; 25. manganese; 26. mercury; 27. molybdenum; 28. nickel; 29. osmium; 30. palladium; 31. platinum; 32. rhodium; 33. silver; 34. tantalum; 35. tellurium; 36. tin; 37. titanium; 38. tungstenium; 39. vanadium; 40. uranium; 41. zinc.

1. They are all, more or less, remarkable for a peculiar lustre, called the metallic. This property of strongly reflecting light, is connected with a certain state of aggregation of their particles, but is possessed, superficially at least, by mica, animal charcoal, selenium, polished indigo;--bodies not at all metallic.

2. The metals are excellent conductors of caloric, and most of them also of electricity, though probably not all. According to Despretz, they possess the power of conducting heat according to the following numbers:--Gold, 1000; platinum, 981; silver, 973; copper, 898; iron, 374; zinc, 363; tin, 304; lead, 179·6.

Becquerel gives the following table of metals, as to electrical conduction:--

Copper, 100; gold, 93·6; silver, 73·6; zinc, 28·5; platina, 16·4; iron, 15·8; tin, 15·5; lead, 8·3; mercury, 3·5; potassium, 1·33.

The metals which hardly, if at all, conduct electricity, are, zirconium; alumium; tantalum, in powder; and tellurium.

3. Metals are probably opaque; yet gold leaf, as observed by Newton, seems to transmit the green rays, for objects placed behind it in the sunbeam appear green. This phenomena has, however, been ascribed to the rays of light passing through an infinite number of minute fissures in the thinly hammered gold.

4. All metals are capable of combining with oxygen, but with affinities and in quantities extremely different. Potassium and sodium have the strongest affinity for it; arsenic and chromium, the feeblest. Many metals become acids by a sufficient dose of oxygen, while, with a smaller dose, they constitute salifiable bases.

5. Metals combine with each other, forming a class of bodies called alloys, except when one of them is mercury, in which case the compound is styled an amalgam.

6. They combine with hydrogen into hydrurets; with carbon, into carburets; with sulphur, into sulphurets; with phosphorus, into phosphurets; with selenium, into seleniurets; with boron, into borurets (borides?); with chlorine, into chlorides; with iodine, into iodides; with cyanogen, into cyanides; with silicon, into silicides; and with fluorine, into fluorides.

7. Metallic salts are definite compounds, mostly crystalline, of the metallic oxides with the acids. See HALOID.

METEORITES, (Aerolithes, Fr.), are stones of a peculiar aspect and composition, which have fallen from the air.

METHYLÈNE, a peculiar liquid compound of carbon and hydrogen, extracted from pyroxilic spirit, which is reckoned to be a bi-hydrate of methylène.

MICA, is a finely foliated mineral, of a pearly metallic lustre. It is harder than gypsum, but not so hard as calc-spar; flexible and elastic; spec. grav. 2·65. It is an ingredient of granite and gneiss. The large sheets of mica exposed for sale in London, are mostly brought from Siberia. They are used, instead of glass, to enclose the fire, without concealing the flame, in certain stoves.

The mica of Fahlun, analyzed by Rose, afforded, silica, 46·22; alumina, 34·52; peroxide? of iron, 6·04; potash, 8·22; magnesia, with oxide of manganese, 2·11; fluoric acid, 1·09; water, 0·98.

MICROCOSMIC SALT; a term given to a salt extracted from human urine, because man was regarded by the alchemists as a miniature of the world, or the microcosm. It is a phosphate of soda and ammonia; and is now prepared by mixing, equivalent proportions of phosphate of soda and phosphate of ammonia, each in solution, evaporating and crystallizing the mixture. A small excess of ammonia aids the crystallization.

MILK; (Lait, Fr.; Milche, Germ.) owes its whiteness and opacity to an emulsion composed of the caseous matter and butter, with sugar of milk, extractive matters, salts, and free lactic acid; the latter of which causes fresh milk to redden litmus paper. Milk, in general, contains from 10 to 12 per cent. of solid matter, on being evaporated to dryness by a steam heat. The mean specific gravity of cows’ milk is 1·030, but it is less if the milk be rich in cream. The specific gravity of the skimmed milk is 1·035; and of the cream is 1·0244. 100 parts of creamed milk, contain--

Caseous matter, containing some butter, 2·600 Sugar of milk 3·500 Alcoholic extract, lactic acid, and lactates 0·600 Salts; muriate and phosphate of potash, and phosphate of lime 0·420 Water 92·875 Cream consists of,--Butter separated by churning 4·5 Caseous matter precipitated by the coagulation of the milk of the butter 3·5 Butter-milk 92·0 ------- 100·0

When milk contained in wire-corked bottles, is heated to the boiling point in a water bath, the oxygen of the included small portion of air under the cork seems to be carbonated, and the milk will afterwards keep fresh, it is said, for a year or two; as green gooseberries and peas do by the same treatment.

MILL-STONE, or BUHR-STONE. This interesting form of silica, which occurs in great masses, has a texture essentially cellular, the cells being irregular in number, shape, and size, and are often crossed by thin plates, or coarse fibres of silex. The Buhr-stone has a straight fracture, but it is not so brittle as flint, though its hardness is nearly the same. It is feebly translucent; its colours are pale and dead, of a whitish, grayish, or yellowish cast, sometimes with a tinge of blue.

The Buhr-stones usually occur in beds, which are sometimes continuous, and at others interrupted. These beds are placed amid deposits of sand, or argillaceous and ferruginous marls, which penetrate between them, filling their fissures and honeycomb cavities. Buhr-stones constitute a very rare geological formation, being found in abundance only in the mineral basin of Paris, and a few adjoining districts. Its place of superposition is well ascertained: it forms a part of the lacustrine, or fresh-water formation, which, in the locality alluded to, lies above the fossil-bone gypsum, and the stratum of sand and marine sandstone which cover it. Buhr-stone constitutes, therefore, the uppermost solid stratum of the crust of the globe; for above it there is nothing but alluvial soil, or diluvial gravel, sand, and loam.

Buhr-stones sometimes contain no organic forms, at others they seem as if stuffed full of fresh-water shells, or land shells and vegetables of inland growth. There is no exception known to this arrangement; but the shells have assumed a siliceous nature, and their cavities are often bedecked with crystals of quartz. The best Buhr-stones for grinding corn, have about an equal proportion of solid matter, and of vacant space. The finest quarry of them is upon the high ground, near La Ferté-sous-Jouarre. The stones are quarried in the open air, and are cut out in cylinders, from one to two yards in diameter, by a series of iron and wooden wedges, gradually but equally inserted. The pieces of buhr-stones are afterwards cut into parallelopipeds, called panes, which are bound with iron hoops into large millstones. These pieces are exported chiefly to England and America. Good millstones of a bluish white colour, with a regular proportion of cells, when six feet and a half in diameter, fetch 1200 francs a-piece, or 48_l._ sterling. A coarse conglomerate sandstone or breccia is, in some cases, used as a substitute for buhr-stones; but it is a poor one.

MINERAL WATERS. See SODA WATER, and WATERS, MINERAL.

MINES; (Bergwerke, Germ.) Amidst the variety of bodies apparently infinite, which compose the crust of the globe, geologists have demonstrated the prevalence of a few general systems of rocks, to which they have given the name of formations or deposits. A large proportion of these mineral systems consists of parallel planes, whose length and breadth greatly exceed their thickness; on which account they are called stratified rocks; others occur in very thick blocks, without any parallel stratification, or horizontal seams of considerable extent.

The stratiform deposits are subdivided into two great classes; the primary and the secondary. The former seem to have been called into existence before the creation of organic matter, because they contain no exuviæ of vegetable or animal beings; while the latter are more or less interspersed, and sometimes replete with organic remains. The primary strata are characterized, moreover, by the nearly vertical or highly inclined position of their planes; the secondary lie for the most part in a nearly horizontal position.

Where the primitive mountains graduate down into the plains, rocks of an intermediate character appear, which, though possessing a nearly vertical position, contain a few vestiges of animal beings, especially shells. These have been called transition, to indicate their being the passing links between the first and second systems of ancient deposits; they are distinguished by the fractured and cemented texture of their planes, for which reason they are sometimes called conglomerate.

Between these and the truly secondary rocks, another very valuable series is interposed in certain districts of the globe; namely, the coal-measures, the paramount formation of Great Britain. The coal strata are disposed in a basin-form, and alternate with parallel beds of sandstone, slate-clay, iron-stone, and occasionally limestone. Some geologists have called the coal-measures the medial formation.

In every mineral plane, the inclination and direction are to be noted; the former being the angle which it forms with the horizon, the latter the point of the azimuth or horizon, towards which it dips, as west, north-east, south, &c. The direction of the bed is that of a horizontal line drawn in its plane; and which is also denoted by the point of the compass. Since the lines of direction and inclination are at right angles to each other, the first may always be inferred from the second; for when a stratum is said to dip to the east or west, this implies that its direction is north and south.

The smaller sinuosities of the bed are not taken into account, just as the windings of a river are neglected in stating the line of its course.

Masses are mineral deposits, not extensively spread in parallel planes, but irregular heaps, rounded or oval, enveloped in whole or in a great measure by rocks of a different kind. Lenticular masses being frequently placed between two horizontal or inclined strata, have been sometimes supposed to be stratiform themselves, and have been accordingly denominated by the Germans liegende stocke, lying heaps or blocks.

The orbicular masses often occur in the interior of unstratified mountains, or in the bosom of one bed.

Nests, concretions, nodules, are small masses found in the middle of strata; the first being commonly in a friable state; the second often kidney-shaped, or tuberous; the third nearly round, and encrusted, like the kernel of an almond.

Lodes, or large veins, are flattened masses, with their opposite surfaces not parallel, which consequently terminate like a wedge, at a greater or less distance, and do not run parallel with the rocky strata in which they lie, but cross them in a direction not far from the perpendicular; often traversing several different mineral planes. The lodes are sometimes deranged in their course, so as to pursue for a little way the space between two contiguous strata; at other times they divide into several branches. The matter which fills the lodes is for the most part entirely different from the rocks they pass through, or at least it possesses peculiar features.

This mode of existence, exhibited by several mineral substances, but which has been long known with regard to metallic ores, suggests the idea of clefts or rents having been made in the stratum posterior to its consolidation, and of the vacuities having been filled with foreign matter, either immediately or after a certain interval. There can be no doubt as to the justness of the first part of the proposition, for there may be observed round many lodes undeniable proofs of the movement or dislocation of the rock; for example, upon each side of the rent, the same strata are no longer situated in the same plane as before, but make greater or smaller angles with it; or the stratum upon one side of the lode is raised considerably above, or depressed considerably below, its counterpart upon the other side. With regard to the manner in which the rent has been filled, different opinions may be entertained. In the lodes which are widest near the surface of the ground, and graduate into a thin wedge below, the foreign matter would seem to have been introduced as into a funnel at the top, and to have carried along with it in its fluid state portions of rounded gravel and organic remains. In other cases, other conceptions seem to be more probable; since many lodes are largest at their under part, and become progressively narrower as they approach the surface; from which circumstance, it has been inferred that the rent has been caused by an expansive force acting from within the earth, and that the foreign matter, having been injected in a fluid state, has afterwards slowly crystallized. This hypothesis accounts much better than the other for most of the phenomena observable in mineral veins, for the alterations of the rock at their sides, for the crystallization of the different substances interspersed in them, for the cavities bestudded with little crystals, and for many minute peculiarities. Thus, the large crystals of certain substances which line the walls of hollow veins, have sometimes their under surfaces besprinkled with small crystals of sulphurets, arseniurets, &c., while their upper surfaces are quite smooth; suggesting the idea of a slow sublimation of these volatile matters from below, by the residual heat, and their condensation upon the under faces of the crystalline bodies, already cooled. This phenomenon affords a strong indication of the igneous origin of metalliferous veins.

In the lodes, the principal matters which fill them are to be distinguished from the accessory substances; the latter being distributed irregularly, amidst the mass of the first, in crystals, nodules, grains, seams, &c. The non-metalliferous exterior portion, which is often the largest, is called gangue, from the German gang, vein. The position of a vein is denoted, like that of the strata, by the angle of inclination, and the point of the horizon towards which they dip, whence the direction is deduced.

Veins, are merely small lodes, which sometimes traverse the great ones, ramifying in various directions, and in different degrees of tenuity.

A metalliferous substance is said to be disseminated, when it is dispersed in crystals, spangles, scales, globules, &c., through a large mineral mass.

Certain ores which contain the metals most indispensable to human necessities, have been treasured up by the Creator in very bountiful deposits; constituting either great masses in rocks of different kinds, or distributed in lodes, veins, nests, concretions, or beds with stony and earthy admixtures; the whole of which become the objects of mineral exploration. These precious stores occur in different stages of the geological formations; but their main portion, after having existed abundantly in the several orders of the primary strata, suddenly cease to be found towards the middle of the secondary. Iron ores are the only ones which continue among the more modern deposits, even so high as the beds immediately beneath the chalk, when they also disappear, or exist merely as colouring matters of the tertiary earthy beds.

The strata of gneiss and mica-slate constitute in Europe the grand metallic domain. There is hardly any kind of ore which does not occur there in sufficient abundance to become the object of mining operations, and many are found no where else. The transition rocks and the lower part of the secondary ones, are not so rich, neither do they contain the same variety of ores. But this order of things, which is presented by Great Britain, Germany, France, Sweden, and Norway, is far from forming a general law; since in equinoxial America the gneiss is but little metalliferous; while the superior strata, such as the clay-schists, the sienitic porphyries, the limestones, which complete the transition series, as also several secondary deposits, include the greater portion of the immense mineral wealth of that region of the globe.

All the substances of which the ordinary metals form the basis, are not equally abundant in nature; a great proportion of the numerous mineral species which figure in our classifications, are mere varieties scattered up and down in the cavities of the great masses or lodes. The workable ores are few in number, being mostly sulphurets, some oxides, and carbonates. These occasionally form of themselves very large masses, but more frequently they are blended with lumps of quartz felspar, and carbonate of lime, which form the main body of the deposit; as happens always in proper lodes. The ores in that case are arranged in small layers parallel to the strata of the formation, or in small veins which traverse the rock in all directions, or in nests or concretions stationed irregularly, or finally disseminated in hardly visible particles. These deposits sometimes contain apparently only one species of ore, sometimes several, which must be mined together, as they seem to be of contemporaneous formation; whilst, in other cases, they are separable, having been probably formed at different epochs. In treating of the several metals in their alphabetical order, I have taken care to describe their peculiar geological positions, and the rocks which accompany or mineralize them.

In mining, as in architecture, the best method of imparting instruction is to display the master-pieces of the respective arts, which speak clearly to the mind through the medium of the eye. It is not so easy, however, to represent at once the general effect of a mine, as it is of an edifice; because there is no point of sight from which the former can be sketched at once, like the latter. The subterraneous structures certainly afford some of the finest examples of the useful labours of man, continued for ages, under the guidance of science and ingenuity; but, however curious, beautiful, and grand in themselves, they cannot become objects of a panoramic view. It is only by the lights of geometry and geology that mines can be contemplated and surveyed, either as a whole or in their details; and, therefore, these marvellous subterranean regions, in which roads are cut many hundred miles long, are altogether unknown or disregarded by men of the world. Should any of them, perchance, from curiosity or interest, descend into these dark recesses of the earth, they are prepared to discover only a few insulated objects, which they may think strange or possibly hideous; but they cannot recognize either the symmetrical disposition of mineral bodies, or the laws which govern geological phenomena, and serve as sure guides to the skilful miner in his adventurous search. It is by exact plans and sections of subterraneous workings, that a knowledge of the nature, extent, and distribution of mineral wealth, can be acquired.

As there is no country in the world so truly rich and powerful, by virtue of its mineral stores, as Great Britain, so there are no people who ought to take a deeper interest in their scientific illustration. I have endeavoured in the present article to collect from the most authentic sources the most interesting and instructive examples of mining operations.

To the magnificent work of Ville-Fosse, Sur la Richesse Minerale, no longer on sale, I have to acknowledge weighty obligations; many of the figures being copied from his great Atlas.

Lodes or mineral veins are usually distinguished by English miners into at least four species. 1. The rake vein. 2. The pipe vein. 3. The flat or dilated vein; and 4. The interlaced mass (stock-werke), indicating the union of a multitude of small veins mixed in every possible direction with each other, and with the rock.

1. The rake vein is a perpendicular mineral fissure; and is the form best known among practical miners. It commonly runs in a straight line, beginning at the superficies of the strata, and cutting them downwards, generally further than can be reached. This vein sometimes stands quite perpendicular; but it more usually inclines or hangs over at a greater or smaller angle, or slope, which is called by the miners the hade or hading of the vein. The line of direction in which the fissure runs, is called the bearing of the vein.

2. The pipe vein resembles in many respects a huge irregular cavern, pushing forward into the body of the earth in a sloping direction, under various inclinations, from an angle of a few degrees to the horizon, to a dip of 45°, or more. The pipe does not in general cut the strata across like the rake vein, but insinuates itself between them; so that if the plane of the strata be nearly horizontal, the bearing of the pipe vein will be conformable; but if the strata stand up at a high angle, the pipe shoots down nearly headlong like a shaft. Some pipes are very wide and high, others are very low and narrow, sometimes not larger than a common mine or drift.

3. The flat or dilated vein, is a space or opening between two strata or beds of stone, the one of which lies above, and the other below this vein, like a stratum of coal between its roof and pavement; so that the vein and the strata are placed in the same plane of inclination. These veins are subject, like coal, to be interrupted, broken, and thrown up or down by slips, dykes, or other interruptions of the regular strata. In the case of a metallic vein, a slip often increases the chance of finding more treasure. Such veins do not preserve the parallelism of their beds, characteristic of coal seams; but vary excessively in thickness within a moderate space. Flat veins occur frequently in limestone, either in a horizontal or declining direction. The flat or strata veins open and close, as the rake veins also do.

4. The interlaced mass has been already defined.

To these may be added the accumulated vein, or irregular mass (butzenwerke), a great deposit placed without any order in the bosom of the rocks, apparently filling up cavernous spaces.

The interlaced masses are more frequent in primitive formations, than in the others; and tin is the ore which most commonly affects this locality. See figure of TIN mine.

The study of the mineral substances, called gangues or vein-stones, which usually accompany the different ores, is indispensable in the investigation and working of mines. These gangues, such as quartz, calcareous spar, fluor spar, heavy spar, &c., and a great number of other substances, although of little or no value in themselves, become of great consequence to the miner, either by pointing out by their presence that of certain useful minerals, or by characterising in their several associations, different deposits of ores of which it may be possible to follow the traces, and to discriminate the relations, often of a complicated kind, provided we observe assiduously the accompanying gangues.

Mineral veins are subject to derangements in their course, which are called shifts or faults. Thus, when a transverse vein throws out, or intercepts, a longitudinal one, we must commonly look for the rejected vein on the side of the obtuse angle which the direction of the latter makes with that of the former. When a bed of ore is deranged by a fault, we must observe whether the slip of the strata be upwards or downwards; for in either circumstance, it is only by pursuing the direction of the fault that we can recover the ore; in the former case by mounting, in the latter by descending beyond the dislocation.

When two veins intersect each other, the direction of the offcast is a subject of interest, both to the miner and the geologist. In Saxony it is considered as a general fact that the portion thrown out is always upon the side of the obtuse angle, a circumstance which holds also in Cornwall; and the more obtuse the angle, the out-throw is the more considerable. A vein may be thrown out on meeting another vein, in a line which approaches either towards its inclination or its direction. The Cornish miners use two different terms to denote these two modes of rejection; for the first case, they say the vein is heaved; for the second, it is started.

The great copper lode of Carharack, d, fig. 699. in the parish of Gwenap, is one of the most instructive examples of intersection. The power or thickness of this vein is 8 feet; its direction is nearly due east and west, and it dips towards the north at an inclination of two feet per fathom; its upper part being in the killas (a greenish clay-slate); its lower part in the granite. The lode has suffered two intersections; the first produced by meeting the vein h, called Steven’s fluckan, which runs from north-east to south-west, and which throws the lode several fathoms out; the second is produced by another vein i, almost at right angles with the first, and which occasions another out-throw of 20 fathoms to the right side. The fall of the vein occurs therefore in the one case to the right, and in the other to the left; but in both it is towards the side of the obtuse angle. This distribution is very singular; for one part of the vein appears to have mounted while the other has descended. N, S denotes North and South. d is the copper lode running east and west. h, i, are systems of clay-slate veins called fluckans; the line over S, represents the down-shift, and d´ the up-shift.

General observations on the localities of ores, and on the indications of metallic mines.

1. Tin, exists principally in primitive rocks, appearing either in interlaced masses, in beds, or as a constituent part of the rock itself, and more rarely in distinct veins. Tin ore is found indeed sometimes in alluvial land, filling up low situations between lofty mountains.

2. Gold, occurs either in beds, or in veins, frequently in primitive rocks; though in other formations, and particularly in alluvial earth, it is also found. When this metal exists in the bosom of primitive rocks, it is particularly in schists; it is not found in serpentine, but it is met with in greywacke in Transylvania. The gold of alluvial districts, called gold of washing or transport, occurs, as well as alluvial tin, among the debris of the more ancient rocks.

3. Silver, is found particularly in veins and beds, in primitive and transition formations; though some veins of this metal occur in secondary strata. The rocks richest in it are, gneiss, mica-slate, clay-slate, greywacke, and old alpine limestone. Localities of silver-ore itself are not numerous, at least in Europe, among secondary formations; but it occurs in combination with the ores of copper or of lead.

4. Copper, exists in the three mineral epochas; 1. in primitive rocks, principally in the state of pyritous copper, in beds, in masses, or in veins; 2. in transition districts, sometimes in masses, sometimes in veins of copper pyrites; 3. in secondary strata, especially in beds of cupreous schist.

5. Lead, occurs also in each of the three mineral epochas; abounding particularly in primitive and transition grounds, where it usually constitutes veins, and occasionally beds of sulphuretted lead (galena). The same ore is found in strata or in veins among secondary rocks, associated now and then with ochreous iron-oxide and calamine (carbonate of zinc); and it is sometimes disseminated in grains through more recent strata.

6. Iron, is met with in four different mineral eras, but in different ores. Among primitive rocks, magnetic iron ore and specular iron ore occur chiefly in beds, sometimes of enormous size; the ores of red or brown oxide of iron (hæmatite) are found generally in veins, or occasionally in masses with sparry iron, both in primitive and transition rocks; as also sometimes in secondary strata; but more frequently in the coal-measure strata, as beds of clay-ironstone, of globular iron oxide, and carbonate of iron. In alluvial districts we find ores of clay-ironstone, granular iron-ore, bog-ore, swamp-ore, and meadow-ore. The iron ores which belong to the primitive period have almost always the metallic aspect, with a richness amounting even to 80 per cent. of iron, while the ores in the posterior formations become in general more and more earthy, down to those in alluvial soils, some of which present the appearance of a common stone, and afford not more than 20 per cent. of metal, though its quality is often excellent.

7. Mercury, occurs principally among secondary strata, in disseminated masses, along with combustible substances; though the metal is met with occasionally in primitive countries.

8. Cobalt, belongs to the three mineral epochas; its most abundant deposits are veins in primitive rocks; small veins containing this metal are found, however, in secondary strata.

9. Antimony, occurs in veins or beds among primitive and transition rocks.

10, 11. Bismuth and nickel do not appear to constitute the predominating substance of any mineral deposits; but they often accompany cobalt.

12. Zinc, occurs in the three several formations: namely, as sulphuret or blende, particularly in primitive and transition rocks; as calamine, in secondary strata, usually along with oxide of iron, and sometimes with sulphuret of lead.

An acquaintance with the general results collected and classified by geology must be our first guide in the investigation of mines. This enables the observer to judge whether any particular district, should from the nature and arrangement of its rocks, be susceptible of including within its bosom, beds of workable ores; it indicates also, to a certain degree, what substances may probably be met with in a given series of rocks, and what locality these substances will preferably affect. For want of a knowledge of these facts, many persons have gone blindly into researches equally absurd and ruinous.

Formerly indications of mines were taken from very unimportant circumstances; from thermal waters, the heat of which was gratuitously referred to the decomposition of pyrites; from mineral waters, whose course is however often from a far distant source; from vapours incumbent over particular mountain groups; from the snows melting faster in one mineral district than another; from the different species of forest trees, and from the greater or less vigour of vegetation, &c. In general, all such indications are equally fallacious with the divining rod, and the compass made of a lump of pyrites suspended by a thread.

Geognostic observation has substituted more rational characters of metallic deposits, some of which may be called negative and others positive.

The negative indications are derived from that peculiar geological constitution, which from experience or general principles excludes certain metallic matters; for example, granite, and in general every primitive formation, forbids the hope of finding within them combustible fossils (pit-coal), unless it be beds of anthracite; there also it would be vain to seek for sal gem. It is very seldom that granite rocks include silver; or limestones, ores of tin. Volcanic territories never afford any metallic ores worth the working; nor do extensive veins usually run into secondary and alluvial formations. The richer ores of iron do not occur in secondary strata; and the ores of this metal peculiar to these localities, do not exist among primary rocks.

Among positive indications, some are proximate and others remote. The proximate are, an efflorescence, so to speak, of the subjacent metallic masses; magnetic attraction for iron ores; bituminous stone, or inflammable gas for pit-coal; the frequent occurrence of fragments of particular ores, &c. The remote indications consist in the geological epocha, and nature of the rocks. From the examples previously adduced, marks of this kind acquire new importance when in a district susceptible of including deposits of workable ores, the gangues or vein-stones are met with which usually accompany any particular metal. The general aspect of mountains whose flanks present gentle and continuous slopes, the frequency of sterile veins, the presence of metalliferous sands, the neighbourhood of some known locality of an ore, for instance that of iron-stone in reference to coal, lastly the existence of salt springs and mineral waters, may furnish some indications; but when ferruginous or cupreous waters issue from sands or clays, such characters merit in general little attention, because the waters may flow from a great distance. No greater importance can be attached to metalliferous sands and saline springs.

In speaking of remote indications, we may remark that in several places, and particularly near Clausthal in the Hartz, a certain ore of red oxide of iron occurs above the most abundant deposits of the ores of lead and silver; whence it has been named by the Germans the iron-hat. It appears that the iron ore rich in silver, which is worked in America under the name of pacos, has some analogy with this substance; but iron ore is in general so plentifully diffused on the surface of the soil, that its presence can be regarded as only a remote indication, relative to other mineral substances, except in the case of clay ironstone with coal.

Of the instruments and operations of subterranean operations.--It is by the aid of geometry in the first place that the miner studies the situation of the mineral deposits, on the surface and in the interior of the ground; determines the several relations of the veins and the rocks; and becomes capable of directing the perforations towards a suitable end.

The instruments are, 1. the magnetic compass, which is employed to measure the direction of a metallic ore, wherever the neighbourhood of iron does not interfere with its functions; 2. the graduated semicircle which serves to measure the inclination, which is also called the clinometer.

3. The chain or cord for measuring the distance of one point from another.

4. When the neighbourhood of iron renders the use of the magnet uncertain, a plate or plane table is employed.

The dials of the compasses generally used in the most celebrated mines, are graduated into hours; most commonly into twice 12 hours. Thus the whole limb is divided into 24 spaces, each of which contains 15° = 1 hour. Each hour is subdivided into 8 parts.

Means of penetrating into the interior of the earth.--In order to penetrate into the interior of the earth, and to extract from it the objects of his toils, the miner has at his disposal several means, which may be divided into three classes: 1. manual tools, 2. gunpowder, and 3. fire.

The tools used by the miners of Cornwall and Devonshire are the following:

Fig. 700. The pick. It is a light tool, and somewhat varied in shape according to circumstances. One side used as a hammer is called the poll, and is employed to drive in the gads, or to loosen and detach prominences. The point is of steel, carefully tempered, and drawn under the hammer to the proper form. The French call it pointerolle.

Fig. 701. The gad. It is a wedge of steel, driven into crevices of rocks, or into small openings made with the point of the pick.

Fig. 702. The miner’s shovel. It has a pointed form, to enable it to penetrate among the coarse and hard fragments of the mine rubbish. Its handle being somewhat bent, a man’s power may be conveniently applied without bending his body.

The blasting or shooting tools are:--

A sledge or mallet fig. 703. Borer -- 704. Claying bar -- 705. Needle or nail -- 706. Scraper -- 707. Tamping bar -- 708.

Besides these tools the miner requires a powder-horn, rushes to be filled with gunpowder, tin cartridges for occasional use in wet ground, and paper rubbed over with gunpowder or grease, for the smifts or fuses.

The borer, fig. 704., is an iron bar tipped with steel, formed like a thick chisel, and is used by one man holding it straight in the hole with constant rotation on its axis, while another strikes the head of it with the iron sledge or mallet, fig. 703. The hole is cleared out from time to time by the scraper, fig. 707., which is a flat iron rod turned up at one end. If the ground be very wet, and the hole gets full of mud, it is cleaned out by a stick bent at the end into a fibrous brush, called a swab-stick.

Fig. 709. represents the plan of blasting the rock, and a section of a hole ready for firing. The hole must be rendered as dry as possible, which is effected very simply by filling it partly with tenacious clay, and then driving into it a tapering iron rod, which nearly fills its calibre, called the claying bar. This being forced in with great violence, condenses the clay into all the crevices of the rock, and secures the dryness of the hole. Should this plan fail, recourse is had to tin cartridges furnished with a stem or tube (see fig. 710.,) through which the powder may be inflamed. When the hole is dry, and the charge of powder introduced, the nail, a small taper rod of copper, is inserted so as to reach the bottom of the hole, which is now ready for tamping. By this difficult and dangerous process, the gunpowder is confined, and the disruptive effect produced. Different substances are employed for tamping, or cramming the hole, the most usual one being any soft species of rock free from siliceous or flinty particles. Small quantities of it only are introduced at a time, and rammed very hard by the tamping-bar, which is held steadily by one man, and struck with a sledge by another. The hole being thus filled, the nail is withdrawn by putting a bar through its eye, and striking it upwards. Thus a small perforation or vent is left for the rush which communicates the fire.

Besides the improved tamping-bar faced with hard copper, other contrivances have been resorted to for diminishing the risk of those dreadful accidents that frequently occur in this operation. Dry sand is sometimes used as a tamping material, but there are many rocks for the blasting of which it is ineffective. Tough clay will answer better in several situations.

For conveying the fire, the large and long green rushes which grow in marshy ground are selected. A slit is made in one side of the rush, along which the sharp end of a bit of stick is drawn, so as to extract the pith, when the skin of the rush closes again by its own elasticity. This tube is filled up with gunpowder, dropped into the vent-hole, and made steady with a bit of clay. A paper smift, adjusted to burn a proper time, is then fixed to the top of the rush-tube, and kindled, when the men of the mine retire to a safe distance.

In fig. 709. the portion of the rock which would be dislodged by the explosion, is that included between A and B. The charge of powder is represented by the white part which fills the hole up to C; from which point to the top, the hole is filled with tamping. The smift is shewn at D.

Fig. 711. is an iron bucket, or as it is called in Cornwall, a kibble, in which the ore is raised in the shafts, by machines called whims, worked by horses. The best kibbles are made of sheet-iron, and hold each about three hundred weight of ore: 120 kibbles are supposed to clear a cubic fathom of rock.

Fig. 712. represents the wheelbarrow used under ground for conveying ore and waste to the foot of the shafts. It is made of light deal, except the wheel, which has a narrow rim of iron.

Fig. 713. represents Mr. Taylor’s ingenious ventilator, or machine for renewing fresh air in mines. It is so simple in construction, so complete in its operation, requires so little power to work it, and is so little liable to injury from wear, that nothing further of the kind can be desired in ordinary metallic mines. The shaft of the mine is represented at A; at either the top or bottom of which the machine may be placed, as is found most convenient, but the foul air must be discharged into a floor, furnished with a valve-door to prevent its return into the mine. B is the air-pipe from the mine, passing through the bottom of the fixed vessel or cylinder C, which is formed of timber, and bound with iron hoops. It is filled with water nearly to the top of the pipe B, on which is fixed a valve opening upwards at D. E, the air, or exhausting cylinder of cast-iron, open at bottom, and suspended over the air-pipe, but immersed some way in the water. It is furnished with a wooden top, having an aperture fitted with a valve likewise opening upwards at F. This exhausting cylinder is moved up and down by the bob G, brought into connexion with any engine by the horizontal rod H; the weight of the cylinder being balanced, if necessary, by the counterpoise I. The action is as follows:--When the cylinder rises, the air from the mine rushes up through the pipe and valve D; and when it descends, this valve shuts, and prevents the return of the air, which is expelled through the valve F. With a cylinder two feet in diameter and six feet long, working from two to three strokes per minute, 200 gallons of air may be discharged in the same time.

Gunpowder is the most valuable agent of excavation; possessing a power which has no limit, and which can act every where, even under water. Its introduction, in 1615, caused a great revolution in the mining art.

It is employed in mines in different manners, and in different quantities, according to circumstances. In all cases, however, the process resolves itself into boring a hole, and enclosing a cartridge in it, which is afterwards made to explode. The hole is always cylindrical, and is usually made by means of the borer, fig. 704., a stem of iron, terminated by a blunt-edged chisel. It sometimes ends in a cross, formed by two chisels set transversely. The workman holds the stem in his left hand, and strikes it with an iron mallet held in his right. He is careful to turn the punch a very little round at every stroke. Several punches are employed in succession, to bore one hole; the first shorter, the latter ones longer, and somewhat thinner. The rubbish is withdrawn as it accumulates, at the bottom of the hole, by means of a picker, which is a small spoon or disc of iron fixed at the end of a slender iron rod. When holes of a large size are to be made, several men must be employed; one to hold the punch, and one or more to wield the iron mallet. The perforations are seldom less than an inch in diameter, and 18 inches deep; but they are sometimes 2 inches wide, with a depth of 50 inches.

The gunpowder, when used, is most commonly put up in paper cartridges. Into the side of the cartridge, a small cylindrical spindle or piercer is pushed. In this state the cartridge is forced down to the bottom of the hole, which is then stuffed, by means of the tamping bar, fig. 708., with bits of dry clay, or friable stones coarsely pounded.[33] The piercer is now withdrawn, which leaves in its place, a channel through which fire may be conveyed to the charge. This is executed either by pouring gunpowder into that passage, or by inserting into it, reeds, straw stems, quills, or tubes of paper filled with gunpowder. This is exploded by a long match, which the workmen kindle, and then retire to a place of safety.

[33] Sir Rose Price invented a cap of bronze alloy, to tip the lower end of the iron rod; a contrivance now generally used in Cornwall. Before the Geological Society of that county introduced this invention into practice, scarcely a month elapsed without some dreadful explosion sending the miner to an untimely grave, or so injuring him by blowing out his eyes, or shattering his limbs, as to render him a miserable object of charity for the rest of his days. Scarcely has any accident happened since the employment of the new tamping-bar. When the whole bar was made of the tin and copper alloy it was expensive, and apt to bend; but the iron rod tipped with the bronze is both cheap and effectual. An ingenious instrument, called the shifting cartridge, was invented by Mr. Chinalls, and is described in the Transactions of the above society.

As the piercer must not only be slender, but stiff, so as to be easily withdrawn when the hole is tamped, iron spindles are usually employed, though they occasionally give rise to sparks, and consequently to dangerous accidents, by their friction against the sides of the hole. Brass piercers have been sometimes tried; but they twist and break too readily.

Each hole bored in a mine, should be so placed in reference to the schistose structure of the rock, and to its natural fissures, as to attack and blow up the least resisting masses. Sometimes the rock is prepared beforehand for splitting in a certain direction, by means of a narrow channel excavated with the small hammer.

The quantity of gunpowder should be proportional to the depth of the hole, and the resistance of the rock; and merely sufficient to split it. Anything additional would serve no other purpose than to throw the fragments about the mine, without increasing the useful effect. Into the holes of about an inch and a quarter diameter, and 18 inches deep, only two ounces of gunpowder are put.

It appears that the effect of the gunpowder may be augmented by leaving an empty space above, in the middle of, or beneath the cartridge. In the mines of Silesia, the consumption of gunpowder has been eventually reduced, without diminishing the product of the blasts, by mixing sawdust with it in certain proportions. The hole has also been filled up with sand in some cases, according to Mr. Jessop’s plan, instead of being packed with stones, which has removed the danger of the tamping operation. The experiments made in this way have given results very advantageous in quarry blasts with great charges of gunpowder; but less favourable in the small charges employed in mines.

Water does not oppose an insurmountable obstacle to the employment of gunpowder; but when the hole cannot be made dry, a cartridge bag impermeable to water must be had recourse to, provided with a tube also impermeable, in which the piercer is placed.

After the explosion of each mining charge, wedges and levers are employed, to drag away and break down what has been shattered.

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