XX. GALVANISM

GALVANI’S DISCOVERY—THE FROGS ELECTRIFIED—EXPERIMENTS—VOLTA’S PILE—THE TEST—ITS USEFULNESS—FARADAY’S “RESEARCHES.”

Galvanism owes its origin to the researches of Galvani, the celebrated professor of Bologna, and we are indebted to what was a mere “accident” for our knowledge of this science.

Before Galvani’s time there had been many instances adduced of animal electricity. The Rev. F. Lunn, in his article upon Electricity,[15] mentions the fact that fire streamed from the head of Servius Tullius when about seven years of age, and Virgil we know refers to flame emitted by the hair of Ascanius—

“Lambere flamma comas, et circum tempora pasci”;

and if any one will comb his or her hair with an ebonite comb in the dark, with what is sometimes called an “india-rubber comb,” the hair will give out sufficient light to enable the operator to see himself in a looking-glass. In olden days it is related that a lady when touched with a linen cloth emitted sparks, and the same phenomenon was observable when a bookseller at Pisa removed his under-garment or vest (De Castro). We are all aware of the electricity of the cat and of certain fishes (see Electricity of Animals in sequel), and “torpedos.” Galvani had of course a knowledge of this property, and had occupied himself for some time making experiments upon the electricity in animals. He was not in his laboratory that day when the great discovery was made by means of the edible frog.

Galvani’s wife was just then in a very delicate state of health, and in accordance with usage had been ordered soup made from frogs. It is related that some of these animals, ready skinned, were lying upon the laboratory table, for the Professor had been just previously investigating the question of what he opined was “animal” electricity; that is, he fancied that muscular motion depended upon that subtle force.

The electric machine was in action, and one of the attendants happening to approach or touch one of the frogs, the man as well as Madame Galvani observed that the limbs were violently agitated. Galvani was at once informed of this, and he made repeated experiments, which showed him that the convulsive movements only took place when a spark was drawn from the prime conductor of the electric machine, and while the nerve was touched by a conductor. Galvani then suspended a number of frogs to a railing by metal hooks, with a view to experiment upon them with atmospherical electricity. But the frogs’ limbs were again agitated when no electricity was apparent, and Galvani after some consideration came to the conclusion that the movement was owing to the position the animals assumed with reference to the metallic bodies. Thus when muscle and nerve were in contact with metallic bodies and connected by metal, the movements of the limbs were observable, and the greater the surface contact the greater was the convulsion. The philosopher next tried various metals, and discovered that the most powerful combination was zinc and silver.

Galvani, in 1791, published his discovery and his theory that the body acted as a Leyden jar, different parts being in a different state of electricity. No sooner were his deductions published than all Europe was in a ferment, and philosophers of all nations were discussing it. Fowler, Valli, Robison, Wells, Humboldt, etc., all were deeply interested, but none of them appear to have arrived at so correct conclusions as did Volta, the physician of Pavia. “Wherever frogs were to be found,” says Du Bois Reymond, “and where two different kinds of metal could be procured, everybody was anxious to see the mangled limbs of frogs brought to life in this wonderful way. Physiologists believed that at length they should realize their visions of a vital power, and physicians thought no cure was impossible.”

But notwithstanding the popular theory, Volta, in his letters to Carallo, while giving a full and clear account of the discovery made by Galvani and his own experiments, attacked and finally defeated the Professor. Volta quite upset Galvani’s Leyden-jar theory; Volta says that it was by accident that Mr. Galvani discovered the phenomenon, and by which he was more astonished than he ought to have been. Volta’s letters will be found in the Philosophical Transactions of the Royal Society (in French), and he attributes the effect to the metals which produced a small amount of electricity. He found that the nerve was acted upon on even parts of a muscle laid upon two different metals, and if those were united, a contraction took place.

“Many experiments were made in all parts of Europe,” says Doctor Roget, and “an opinion had been very prevalent that the real source of the power developed existed in the muscle and nerve which formed part of the circuit, and that the metals which composed the other part acted merely as the conductors by which that agency was transferred from the one to the other of these animal structures. But the discoveries of Volta dispelled the error, by proving that the sources of power were derived from the galvanic properties of the metals themselves when combined with certain fluids,” and decided that this principle was electricity. From this the “general fact” was deduced—viz., “that when a certain portion of a nerve which is distributed to any muscle is made part of a galvanic circuit, convulsions, generally of a violent and convulsive kind, are produced in that muscle.”

Volta at length made the discovery that when two metals were brought together electricity was developed, and by uniting a disc of copper and one of zinc, and subjecting them to the test of an Electroscope, he found positive and negative electricity developed in the zinc and copper respectively; so Volta came to the conclusion that each metal parted with electricity, and one became all “positive” and the other all “negative.” But when he came further to consider the possibility of building up a “pile” of these metal discs sufficiently strong to produce electric effects, he found that if his theory were correct he would lose from one side of the metal all he would gain from the other, and therefore he could never obtain more than the slight effect he had originally produced.

This was at first a difficulty apparently impossible to remove. It was so self-evident that the discs of metal, if placed in a pile in a series of pairs, would continually exercise like effects to the first pair of discs, that Volta was puzzled, and for some time he could not arrive at any reasonable solution. At last it struck him that if he placed between the discs some slow-conducting substance, the electricity would not pass from disc to disc, and the force developed or set in motion would be more powerful.

He made the experiment. The result was the Voltaic pile made in 1800, of which we give an illustration (fig. 219). A communication on the subject of Electricity by contact, written by M. Volta, is to be found in the Philosophical Proceedings for the year 1800.

Volta constructed the pile which bears his name, on the assumption that “every two heterogeneous bodies form a galvanic circle or arc in which electricity is generated.” The “pile” consisted of a number of discs of zinc and copper separated by discs of card soaked in water. This combination of metals separated by a bad conductor, developed considerable electricity, the “positive” going to the zinc at the top, and the “negative” turning to the opposite end. By touching the zinc and copper extremities simultaneously with wetted fingers we shall experience a shock. “I don’t need your frog,” Volta said, when he had proved his theory; “give me two metals and a moist rag, and I will produce your animal electricity. Your frog is nothing but a moist conductor, and in this respect it is inferior to my wet rag!”

After this discovery the theory of animal electricity died away for many years, till in 1825, Nobili, and afterwards Matteucci, proved the existence of galvanic currents in muscles.

After Volta had succeeded in obtaining a shock from his “pile,” he proceeded to the construction of another instrument, or rather apparatus, which he denominated “Couronne des tasses” (fig. 220). It consisted of a series of small glasses containing water or a saline solution. He then procured a number of “metallic arcs,” partly composed of zinc and partly of copper; these were inserted into the glasses, so that every glass contained the zinc of one and the copper of another arc, not in contact, but one at the right hand the other at the left. The electro motion, supposed to be the primary cause of the galvanic action, was thus produced as well as from the “pile.” The principle was just the same in both apparatus, the metals being divided by the water in one case, and by a wet card or cloth in the other.

Volta, in 1800, addressed to the Royal Society his celebrated letter upon electricity excited by contact of conducting substances, and then the English philosophers proceeded to make further experiments. It was Fabroni of Florence who had just before suggested that chemical action was really the cause of the phenomena exhibited. Sir Humphrey Davy warmly advocated this theory, and made numerous experiments with the view to establish it. Nicholson, Carlisle, and Cruickshank also paid great attention to the subject. Volta, although he had laid the foundation, did not venture to build upon it. Messrs. Nicholson and Carlisle found the two kinds of electricity in the pile, the zinc being positive and the silver negative. They also found that the water was decomposed both in the circuit and in the body of the pile. Subsequently Cruickshank confirmed Nicholson’s observations, and made use of what is termed the “trough” apparatus. He found that hydrogen was emitted from the silver or upper end, and oxygen from the other.

These discoveries opened up a wide field. “The power of the pile in decomposing chemical substances was now established.” Dr. Henry employed galvanism for analysis, and Sir Humphrey Davy invented new combinations of substances. He formed a pile of charcoal and zinc, and found out that a pile could consist of only one metal, different fluids being applied to the opposite surfaces separated by water, and one fluid “capable of oxidating the metal, the other of preventing the effect of oxidation.” Soon after a pile was made of charcoal.

In 1806, Sir H. Davy gave the results of his researches to the world upon the electro-chemical action of bodies. In the course of his experiments he found out the chemical constituents of the alkalies, and a surprising number of new things were brought to light, and chemical science received a most astonishing ally. Sir W. S. Harris says: “A series of new substances were speedily discovered, the existence of which had never before been imagined. Oxygen, chlorine, and acids were all dragged, as it were, to the positive pole, while metals, inflammable bodies, alkalies, and earths became determined to the negative pole of the (galvanic) battery. When wires connected with each extremity of the new battery were tipped with prepared and well-pointed charcoal, and the points brought near each other, then a most intense and pure evolution of light followed, which on separating the points extended to a gorgeous arc.” So the elements of all bodies were separated and the composition of their compounds closely investigated.

Michael Faraday threw himself con amore into the question. He set about to classify the pile phenomena, and arranged them with appropriate terms, and in a series of papers, between the years 1830 and 1840 (see his “Experimental Researches”), he explained the chemical effects of voltaic electricity and electro-magnetic induction. He showed that the electricities obtainable from the voltaic pile and the electrical machine are essentially the same in their action. He proved that the theory held respecting the necessity for the presence of water in electro-chemical composition was erroneous, and that many other fluids and compounds were equally effective. We have not space at our disposal to include a digest of his various lectures and papers. He calculated that as much electricity is employed in holding the gases oxygen and hydrogen together in a grain of water, “as is present in a discharge of lightning.” When water is decomposed by the electric current, the force which determines the oxygen and acid matter held in solution to the positive, while the hydrogen passes to the negative pole, is not in the poles, but in the body decomposed, he says. “The poles,” writes Faraday, “are merely the surfaces or doors by which the electricity enters into or passes out of the decomposing substance. They limit the extent of that substance in the course of the electric current, being its termination in that direction. Hence the elements evolved passed so far and no farther.” Faraday named the poles “electrodes”—the way (in or out) of electricity.

A very simple voltaic pile may be constructed with “gold-leaf” paper. Take two sheets of the gold paper and paste them back to back, and two of silver paper; cut them into discs about the size of a five-shilling-piece (or even of half-a-crown), and place them one on the top of the other, so as the gold and silver may be alternate; press the discs together slightly when a good many layers have been piled up, and introduce them into a glass tube; close the ends of the tubes with corks through which wires are passed from the discs top and bottom. It will be found that the ends are charged with opposite electricities. This is the Zamboni pile, or the dry pile, which was constructed of hundreds of paper discs “tinned on one side, and covered with binoxide of manganese on the other,” put into a tube, and closed with brass stoppers. The electricity will last a long time in a dry pile.

In the accompanying illustration of the Galvanic Pile a disc of copper is at the bottom and a disc of zinc at the top. The latter, P, is the positive pole; the former, N, the negative. When the wires are united the current is closed, and no sign of disturbance can be detected, although the action, of course, is proceeding within the pile. The opposite kinds of electricity neutralize each other, and if a continuous supply were not kept up the electricity would disappear; but as it is, a powerful current is obtained, and if the wire be divided a spark will be observed.

There are many forms of galvanic batteries. The Trough Battery or Cruickshank has been mentioned. There is Wollaston’s Pile, Bunsen’s Battery, Grove’s Battery, and Daniell’s, called the “Constant” Battery. In this last a porous earthenware cell is placed within a cylinder of copper; in the cell a rod of zinc is inserted, the cell being filled with diluted sulphuric acid,—one part of acid to ten parts of water,—and in the outer cylinder is a solution of sulphate of copper.

The cut above illustrates Daniell’s Battery (fig. 223) with connectors.

In Bunsen’s Battery (or the Zinc-Carbon Battery), which is very like the “Daniell” arrangement, as will be seen from the plates (figs. 222, 223), the porous cell has a prism of carbon immersed in it, and is apparently a modification of the powerful “Grove” Battery (fig. 224). This consists of slips of platinum, h, placed in porous cells, g, each cell being surrounded by a glass cylinder. The outer (glass) cells are filled, or nearly filled, with diluted sulphuric acid; nitric acid is used in the porous cells, and a platinum plate inserted. The chemical action of the Grove cell is thus explained by Professor Stewart: “The zinc dissolves in the dilute sulphuric acid, and during this process hydrogen gas is given off. But this hydrogen does not rise up in the shape of bubbles; it finds its way into the porous vessel which contains the strong nitric acid. It there decomposes the acid, taking some oxygen to itself, so as to become water (hydrogen and oxygen forming water), and thereby turning the nitric into nitrous acid, which shows its presence by strong orange-coloured fumes.” By this decomposition of the nitric acid the polarization of the platinum (due to hydrogen) is avoided. The porous cell, while keeping the liquids apart, does not interfere with the chemical action.

A great number of cells are used in the Grove Battery; perhaps even a hundred may be employed.

Smee’s Battery consists of a plate of platinized silver, S, with a bar of wood to prevent contact with the zinc on each side, Z. These are immersed in a glass jar, A, which contains dilute sulphuric acid. The current is obtained by metallic communication with the binding-screws on the top. This battery has much the same general arrangement as Wollaston’s—the position of the plates being, however, reversed; in the latter there are two negative plates to one positive. In Smee’s Battery there are two positive (zinc) plates to one negative plate.

It will now be understood how an electric current is produced; the electricity passing through the cells, etc., to wires, confers certain properties upon the wires, and we can ascertain the effect of the current by means of a Galvanometer, an instrument used to detect the strength and direction of electric currents. The current will evolve heat and light; it will excite muscular action, and will decompose substances into their constituent elements. The deflection of the magnetic needle by the electric current is considered the best evidence of its power; it is on this that the Galvanometer is based.

We can perform a few simple experiments with the current. Suppose, for instance, that a piece of fine wire be fixed between the pole wires of the battery; it will be heated “white hot.” Or if two carbon points be approached in a glass of water, as in the illustration (fig. 227), they will emit a brilliant light in the fluid from the voltaic arc which has given us the electric light. The current is the passage of electricity along the wire, and continues until the working power or “potential” of one conductor is equal to that of the other. When they become equal of course the action ceases, as there is equilibrium. But when an apparatus like the galvanic battery is brought to bear so that the force of electricity from one conductor is made always greater than that of the other conductor, we have a continuous flow while the action of the battery goes on. One view of the principle is thus expressed by Professor Gordon:[16]

“If two metals be placed near together, but not in contact, in a liquid which acts chemically more upon one than upon the other, the metals become charged, so that the one least acted on is of higher potential than the one most acted on. The difference of potential produced depends only upon the nature of the metals and of the liquid, and not on the size or position of the plates. As soon as the difference of potential has reached its constant value the chemical action ceases.

“If now the metals are connected by a wire outside the liquid the difference of potential begins to diminish, and an electric current flows through the wire. As soon as the difference of potential becomes less than the maximum for the metals and liquid, chemical action recommences and brings it up to the maximum; and thus if no disturbing cause interferes the current will continue until the metal most acted on is entirely dissolved.”

The metal most acted on is considered the “generating plate,” and is “positive.” The other attacked less is “negative,” and is known as the “collecting plate,” and the zinc is the positive plate. Sir W. Thomson has shown that the electrical movement in the galvanic circuit is entirely due to the electrical difference produced at the surfaces of contact of the dissimilar metals. The electro-motive force obtained is not the same with all metals. We have mentioned that some are electro-positive and some electro-negative, and it is with reference to each other that the metals are considered to be endowed with these properties respectively. It all depends how the metals are arranged or coupled. With reference to their behaviour in this respect scientists have arranged them in a series, as follows:—

1. Zinc. 2. Cadmium. 3. Tin. 4. Lead. 5. Iron. 6. Nickel. 7. Bismuth. 8. Antimony. 9. Copper. 10. Silver. 11. Gold. 12. Platinum. 13. Graphite.

Each metal in the list is arranged so that it is electro-positive to any one below, and electro-negative to any one above it.

There is another curious fact which should be mentioned. In associating these metals it has been found that when two are brought into contact the electro-motive force becomes greater the more distant they are in the series given above; in other words, the force between any two is equal to the sum of the forces between those intervening between those two. So when zinc is used with copper its force is not so great as when used with platinum.

It was Herr G. S. Ohm who laid down the law that the strength of the electric current is equal to the electro-motive force divided by the resistance, for he proved that the “resistance was inversely proportional to the strength of a current.”

There are two other laws respecting currents; viz.,—

(1.) Parallel currents in the same direction attract each other.

(2.) Parallel currents in opposite directions repel each other.

Upon these two hang all the varied phenomena of electro-dynamics. That chemical action develops electricity we can perceive with the aid of the two cuts (figs. 228 and 229). If the wires be attached to the collecting-plate of a condenser of electricity and the metal plate of a cell, as shown in the figure (fig. 228), the electricity on the plate will be negative. If the operation be reversed, and the plate be put in connection with the acid, and the metal with the earth, the instrument will be charged with positive electricity. In the other case, when two cups are used, united by a magnet so that the solutions (one acid and the other alkaline) can by capillary attraction unite upon the binding of the magnet, and we place the wires as in fig. 229, the charge on the plate will be positive if it be in connection with the acid, and negative if in communication with the alkaline solution. Every time there is chemical action between two bodies in contact electricity is produced—positive on one negative on the other, and that is the fundamental principle of the voltaic pile.

The decomposition of water can also be effected by means of the electric current. If two tubes or vessels be placed in a vase of water, and the wires from the battery be inserted in them respectively, the oxygen will go to the platinum or positive pole wire, and the hydrogen to the zinc or negative pole. This decomposition or “splitting up” of components was termed ELECTROLYSIS by Faraday, who gave a series of names to the action and the actors in these phenomena (fig. 230).

Any liquid body, such as the water we have just decomposed for instance, Faraday termed an electrolyte; the surfaces where the current enters or leaves the body were called electrodes—the “ways,” from odos, a “way”; the entry is the anode; the leaving point the katode, from ana, “up,” and kata, “down.” The electrolyte is divided into two portions, “ions” (“movers”), which move towards the electrodes, which are positive and negative. In the case of the decomposition of water the hydrogen goes to the negative electrode, the oxygen to the positive.

There are a few observations to be made respecting electrolysis. One rule is, that it “never takes place unless the electrolyte is in a liquid state.” The liquid state is essential. It is also observed that the components go to the different electrodes; such elements as go to the negative electrode are termed electro-positive, the others electro-negative; or, as Faraday termed them, “anions” or “kations:” The chemical power or electrolytic action of the current is the same at all parts of the circuit; the quantity of the substance decomposed is in exact proportion to the strength of the current. Faraday measured the strength of the electric current, and invented for the purpose an instrument called the Voltameter. We have mentioned the Galvanometer more than once, and will proceed to describe it. There are several forms of this instrument: the Tangent, the Marine, and the Reflecting Galvanometers, and the Astatic, or “Multiplier.” In the first-named the direction of the current is determined by Ampère’s rule, which is as follows:—

“Imagine an observer placed in the wire so that the current shall pass through him from his feet to his head; let him turn his face to the needle: its north pole is always deflected to his left side.”

The “Tangent” Galvanometer consists of a vertical circle like an upright ring, across which is a support in the centre holding a copper wire, through which the electric current passes. On this point (where the wire is) a needle is very lightly supported, and when the instrument is to be used it is placed so that the plane of the circle is parallel to the line in which the needle points. The current passes, and the needle is deviated. By noting which side the north end of the needle goes the direction of the current is ascertained, and the length of the needle being small in comparison with the diameter of the circle through which the current passes, the strength of the current in the vertical circle is in proportion to the tangent of the angle through which the needle turns. Hence the term “Tangent” Galvanometer.

The “Reflecting” instrument is the invention of Sir William Thomson, in which a mirror is attached to the needle, and reflects a small focus of light upon a scale. The movements, however minute, are easily read. Sir W. Thomson’s Galvanometers are extremely sensitive. We need not mention any other varieties, as full descriptions can easily be obtained. We only need to indicate the mode of working.

The accompanying illustration (fig. 231) shows an Astatic Galvanometer which may be used in two ways—either to measure strength of current, or to find out a current; in the latter case it would be termed a Galvanoscope. It is a compound needle instrument, and consists of two needles placed in parallel directions with opposite poles above each other in a coil. The wire coil is wound round a bobbin, and the astatic needle is placed therein and suspended freely, as in the illustration, by a cocoon thread. The upper needle moves upon a scale, O O, and the instrument is enclosed in a glass shade. The screw, V, communicates with the upper needle, and fixes it at zero point when ready for use. The wires are fastened to the binding-screws, and the current is then sent. The needle is deflected accordingly, and the number of degrees on the scale can be read off.

The uses of the galvanic current are many. Amongst them Electroplating is perhaps the most generally useful, though Electrotyping is also a very important process in art. A visitor to Birmingham may view the process carried on there by some enterprising firms, who have succeeded wonderfully in producing electro-plate. The principle is very simple and easy to understand, but the greatest care and watchfulness are required on the part of the men employed. The principle, as we have said, is simple, and consists in the fact that if a plate of metal be suspended and attached to the positive pole of a galvanic battery and immersed in a solution of the same metal, the conducting substance hung opposite at the negative pole becomes coated with the metal immersed in the solution.

Suppose we take a plate of silver, and immerse it in cyanide of silver dissolved in cyanide of potassium; a coating of silver will be deposited upon the nickel spoon or other article suspended at the other pole. But to make the coating adhere the spoons, forks, etc., are prepared for the bath by cleansing in caustic potash to remove grease, and washed in nitric acid to remove all traces of oxide, then are scoured with sand. Next, a thin coating of mercury is put on by immersion in solution of nitrate of mercury. Finally, they are hung in the bath. A metal rod is hung across the bath (fig. 232), and the plate is immersed. If the rod to which the articles are suspended be attached to the zinc or negative pole, and the plate of silver to the positive pole of the battery, decomposition begins, and the silver begins to attach itself to the suspended objects. If it be desirable to give the plated articles a thick coating, they are retained for a long time in the bath, which is of some non-conducting material. The dull appearance is easily removed by brushing and burnishing, and then the “Electro-plate” is ready for the warehouse. The gilding process is performed in the same manner, a gold plate being substituted for the silver.

ELECTROTYPING may be briefly explained as follows:—Take two vessels, A and B, and in one, A, put some dilute sulphuric acid and two plates, one of zinc, Z, the other of copper, D, but be sure they are not touching each other; each of these plates must have a piece of wire fastened, by soldering to their upper parts. In the vessel, B, put some solution of sulphate of copper and a small quantity of dilute sulphuric acid, and attach another copper plate to the wire which comes from the copper plate in the acid; this second copper plate is to be immersed in the solution of sulphate of copper, and to the wire from the zinc plate is to be fixed the object to be coated. If a medallion or other object in plaster, it should be soaked in very hot wax and then brushed over with blacklead until the surface is perfectly blackened and bright; the wire should be bound all round the margin and soldered (as it were) with melted wax to the medallion, taking care that this wax also is well coated with blacklead. If the object be now immersed in the sulphate of copper solution and kept at a short distance from the plate (it must not touch it), a coating of copper will soon cover the surface and form a perfect cast, which, when of sufficient thickness, may be removed by filing the edge all round. If instead of the plaster cast a copper coin or other copper object be used, the blackleading is not required, but the surface must be first made clean and bright.

Many uses are made of the galvanic current by medical men. If the circuit of the pile is closed and we take a wire in each hand and break contact, a concussion will be felt in the joints of the arm and fingers, and a certain contraction of the muscles. The currents of electricity cause the shocks, and by a peculiar arrangement by which the circuit can be closed or broken at pleasure, a series of shocks can be sent through the body when it forms the connection between the poles of the battery. We give illustrations of a medico-galvanic machine. In fig. 235 there are two batteries, A and B, with cells, C D. Each battery consists of a central plate of platinized silver separated from the zinc plates by a piece of wood, E and F; the binding-screws are fastened to the silver plates, and G H retain the zinc plates; I is a copper band connecting the zinc plate of one battery with the silver plate of the other. At Z and opposite are wires leading to the coil machine. The quantity and intensity of the current are regulated respectively by the indicator, O, and the wires, Q. There is a point, R S, for the breaking of the contact; P N are screws retaining the wires which lead to the handles, U V, grasped by the patients.

The electric current is employed in many diseases, and is of great use in some cases, but the further consideration of it with reference to its medical applications does not fall within the scope of our present work. We will now pass on to one of the most useful applications of the electric force, the Telegraph, and in dealing with it we must make a few remarks upon magnetism. First, let us make an experiment or two, and see the reciprocal action between electricity and magnetism.

(1.) If we take a piece of iron of the form of a horse-shoe (fig. 236), and wind around it copper wire, and pass through the wire an electric current from our battery, the iron will exhibit strong magnetic properties, which it will lose when the current is interrupted. The conducting wires are insulated with silk, and the current will then travel in one direction.

(2.) If we cover the ends of a non-magnetic piece of iron with coils of wire, and rotate the magnet, A B, so as to cause the poles to approach each end of the iron alternately, an electric current will be established in the wire.

(3.) Referring to the first experiment, if we bring a needle in contact with the iron horse-shoe, while the current is passing through the wire we shall find that the needle has become a magnet; i.e., that it will point due north and south when suspended.

We will now see what a Magnet is, and why it has obtained this name.

In Magnesia, in Lydia, in olden times was found a stone of peculiar attributes, which had the property of attracting small portions of iron. The Chinese were acquainted with it, and nowadays it is found in many places. In our childhood we have all read of it in the story of “Sinbad the Sailor.” Popularly it is known as the loadstone; chemists call it magnetic oxide of iron (F_{2}O_{3}). This stone is a natural magnet. In Sweden it exists in great quantities as “magnetic iron,” for it has a great affinity for that metal.

If we rub a piece of steel upon the loadstone we convert the former into a magnet—an artificial magnet as it is called, and the magnetic needle so useful to us in our compasses and in the working of one form of the electric telegraph is thus obtained. Let us see how this needle acts.

Take a magnetic needle and dust upon it some iron filings. You will observe that the filings will be attracted to both ends of the magnet, but the centre will remain uncovered. The ends of a magnet are termed “poles,” the centre the equator. So one end is north and the other south, and we might perhaps imagine that the same characteristics would abide in the bar when it is cut in two. But we find that as when a worm is divided, each portion gets a new head or tail, and makes a perfect worm, so in the magnet each divided half becomes a perfect magnet with separate poles, one of which always points to the north.

The poles of the magnet display the same phenomena as regards attraction and repulsion, as do the opposite kinds of electricity. If we suspend a magnet and bring the north pole of another to the north pole of the suspended magnet, the latter will turn away; but if we apply the north pole of one to the south pole of the other they will be attracted just as opposite electricities attract each other.

MAGNETIZATION is the term applied to the making of artificial magnets, which act is accomplished by bringing the needle in contact with other magnets, or sometimes by means of the electric current. If we carefully stroke the needle with the magnet, always in the same direction, lifting the magnet and beginning afresh every time, we shall magnetize the needle, but with a different polarity from the pole it was rubbed with. A magnet rubbing its north pole against a needle will make the latter’s point south, and vice versâ.

Now that we have seen how the “magnetic needle” is arrived at, we can proceed to explain the electric telegraph. The term telegraph is derived from the Greek words tele, “far,” and graphein, “to write,” and now includes all modes of signalling. Signalling, or telegraphing, is of very ancient origin; the Roman generals spelt words by fire. The beacons fired on the hills, the “Fiery Cross,” and other ancient modes are well known. The semaphore and flags have long been and are still used as modes of signalling, while the flashing of the heliograph “telegraphs” to a distant camp.

The Semaphore was invented by Chappé, and was really the first practical system of telegraphy. It was adopted in 1794, but before this, in 1753, a letter appeared in the Scots Magazine, by Charles Marshall, suggesting that signals should be given by means of electric wires, equal in number to the letters of the alphabet. Soon afterwards Lesage, of Geneva, made an electric telegraph to be worked by frictional electricity, and many ingenious attempts were subsequently made to utilize electricity for signalling purposes, but without any permanent success; indeed, the British government were quite content with their semaphores, for they wrote that “telegraphs of any kind are now wholly unnecessary, and no other than the one now in use will be adopted”!

The Electric Telegraph has had considerable antiquity claimed for it, but it is pretty certain that the discovery made by Doctor Watson, in 1747, that electricity would pass through wires, and that the earth would complete the circuit, gave the first impetus to the Electric Telegraph. Doctor Watson was enabled to transmit shocks across the Thames, and made experiments at Shooters Hill. Franklin did likewise across the Schuykill in 1748, and De Luc performed the same experiments on the Lake of Geneva. Both Lesage and Lomond caused pith balls to diverge at distant points, and in 1794 Reizen made use of the electric spark for transmitting signals, and made strips of foil show out certain letters when the spark passed. He had a wire and a return wire for each letter of the alphabet.

These were all slow advances, and subsequently many learned men in Europe sought to improve upon the ideas then promulgated. We read of telegraphs constructed at Madrid by Salvá and Betancourt in 1797 and 1798, one extending for more than twenty miles. The first-named gentleman finally proposed to substitute the Voltaic pile for the usual machine, and Ronalds and Dyar in England and New York respectively employed frictional electricity with some success. The latter sent charges of frictional electricity through a wire, and they were recorded by being made to pass through litmus paper. The distances between the discharges were intended to indicate the letters of the alphabet, but even if the experiment was fairly tried it failed, for little was heard of the result.

After the invention of Volta’s pile, which Salvá wished to adopt, Sömmering began his experiments. He used thirty-five wires, set up vertically at the bottom of a glass reservoir of water, and terminating in gold points. These wires ended in the opposite direction in brass plates attached to a bar of wood. At one end the points and at the other the plates bore the same letters respectively; hydrogen at one gold point, and oxygen at another, and two different letters were indicated when the current was sent through any two plates. This arrangement was afterwards improved upon, and only two wires retained.

It was not until electro-magnetism had been developed, however, that Œrstead found out the power of electricity to deflect the magnetised needle, and in 1820, Scheweigger added a “multiplier.” Then came Arago into the field with his discovery, that a “wire carrying a current could magnetise a steel rod.” Ampère substituted a helix for a straight wire, and Sturgeon used soft iron for steel, and developed the electro-magnet. Daniell’s battery, and Faraday’s discoveries of magneto-electricity and the induction coil were the means of putting a constant supply of electricity at the service of the telegraph and so on, till 1830 brought out a more practical method introduced by Schilling.

In that year Baron Schilling made a telegraph, and exhibited it in 1832 at Bonn. This invention, with five vertical needles, was shown to Mr. Cooke in 1836. But in 1834, Gauss and Weber had succeeded in sending signals by means of a voltaic current acting upon a magnetised needle, and this apparatus was really the first practical electric telegraph in use, and it was much improved by Professor Steinheil of Munich. They employed a magnetic-electro machine, and caused a bar to move in certain directions to indicate certain letters of the alphabet. This was really of value, but Steinheil, the pupil of Gauss, assisted by his government, employed only a single wire, and made the earth complete the circuit for him instead of having a return wire as his predecessors had. This telegraph was perfected by a series of bells, which gave different tones for different letters, and he also caused the needle to make certain tracings as it moved upon a paper slip, something like the Morse pattern, which was completed in 1837.

Professor Morse, in 1832, conceived the idea of an electric telegraph but his claim was disputed by a Doctor Jackson, who was on the same vessel when the subject was discussed. We need not enter into the details of the controversy. Mr. Morse won the day, and patented his invention.

“It was once a popular fallacy in England and elsewhere that Messrs. Cooke and Wheatstone were the original inventors of the electric telegraph. The electric telegraph had, properly speaking, no inventor.... Messrs. Cooke and Wheatstone were, however, the first who established a telegraph for practical purposes comparatively on a large scale, and in which the public were more nearly concerned.... Therefore it was that the names of these enterprising and talented inventors came to the public ear, while those of Ampère and Steinheil remained comparatively unknown.[17] The telegraph, as used in Great Britain, was the result of the co-operation of Professors Cooke and Wheatstone.

Mr. Cooke, in 1836, having seen the needle telegraph when in Heidelberg, made certain designs, and soon entered into partnership with Professor Wheatstone for the application of electric telegraphs to railways. Their apparatus with five needles and five wires was put up on the London and North-Western (then London and Birmingham) and Great Western lines, but proved too expensive. The instrument was subsequently modified, and is used on the English railways still.

We may now proceed to look at the Wheatstone needle telegraph and see the method of working it. We know already that when a pair of metallic plates are immersed in a fluid which acts chemically more rapidly on the one than the other, and a wire connects the upper parts of these plates, this wonderful agency is set in motion, and circulates from the one plate to the other (fig. 242). This arrangement may be best shown by using one plate of zinc and the other of copper, and a dilute solution of sulphuric acid for the liquid; this, however, produces by far too little of the agent to be used on a telegraphic line, there are therefore combinations of such pairs of plates, so arranged that the power of one pair shall be added to the next in such a way that at the end of the series (called a “battery”) there shall be a great increase of the power accumulated; this arrangement is shown in fig. 244. Now (if the power be sufficient) it does not signify what length of wire there may be between the two ends of this arrangement or “battery”; whether they be connected by a few feet or many hundred miles, the electricity passes instantaneously from one end to the other; and furthermore, it has been found in practice, that this electrical influence can be transmitted through the earth in one direction if sent by a wire in the other; for instance, if a wire from one end of the battery be carried on from London to Liverpool, instead of having another from Liverpool to London, to connect the two ends of the battery, it is found to answer the same purpose if the end of the wire at Liverpool be fastened to a plate of metal buried beneath the surface of the earth, and the other end of the battery at London furnished with a similar plate, also buried. In this arrangement, the electricity will pass beneath the surface of the earth from Liverpool to London, and through the wire from London to Liverpool, thus completing the circuit. The end from which the electricity passes is called the “positive electrode,” that to which it returns, the “negative electrode.” Fig. 245 will show this arrangement.

If a bar-magnet be suspended on a pivot so that it may turn freely, it will (as is well known) turn with one end to the north, which is owing to a current of natural electricity passing round the earth in the direction of east and west, the magnet crossing the current at a right angle; and if a coil of wire coated with silk (to keep one part of the coil from another) be placed round, above, and below the long axis of a bar of steel, as shown at fig. 246, and a current of electricity passed through the wire, the steel becomes a magnet, and will take a direction similar to the natural magnet, more or less, at right angles to this coil, as in fig. 247, according to the intensity of the current; and the instant this electrical current is stopped, it will resume its former direction. This fact has been made use of to form the principal feature of all English telegraphs; such a needle is mounted in an upright position, and instead of its tendency to turn to the north, a tendency to maintain the upright position is given to it by having one of the arms of the magnet a little heavier than the other; such a magnet having a coil of wire surrounding it. When the electric current passes through the coil, it will turn out of the upright position to either one side or the other, according to the direction of the current, from its tendency to assume a position at an angle thereto (fig. 248); if the current be stopped even for an instant, then the needle, or magnet, will again assume its upright position. The pivot of this magnet is brought forward, and has on its front part another needle, which turns with it; this is visible on the outside of the apparatus, and is looked at to ascertain the movement of the one within. There is also an arrangement called a “commutator,” so contrived, that by moving a handle to the right or left, a connection shall be made with either end of the battery, and thereby cause the direction of the current and needle to be changed at pleasure; also by moving the handle into an upright position the current shall be stopped; and finally, by a third movement, a bell shall be rung. Now, as has already been explained, when the current goes in one direction, the magnetic needle is deflected in that direction; and when the current is reversed the position of the needle is also reversed, and when the current is cut off the needle will resume its perpendicular position. If two such needles and two such handles be at each station, when the handles at one station are moved, the needles at the other station will take on a similar movement; and when the handles at that station are moved, the needles at the first station will be moved to correspond. This constitutes the system of communication kept up by the electric telegraphs in England; but it remains to be shown how all the letters of the alphabet and numerals can be represented by the movements of the two handles. These handles can be placed in eight positions (besides the upright one) by a single movement of each hand, as may be seen in fig. 249; and these eight signals if repeated, or made twice in rapid succession will make eight more, and by being repeated three times will constitute a third eight, making twenty-four; finally, by a rapid motion right and left, they may be caused to signify a fourth eight, or thirty-two signals, which are found to be sufficient for every purpose, and by practice may be both produced and read off with facility. Before a message is about to be delivered the commutator is so placed as to ring a bell, which is done by the same arrangement as in a common alarm-clock, but the action is set in motion by a peculiar contrivance, which depends upon the property a bar of soft iron has of becoming magnetic when a wire is wound round it and a current of electricity passed through this wire; this magnetic property exists only as long as the current passes, and stops the instant it is cut off. The catch of the alarm is disengaged by the movement of a bar of iron being drawn to the magnet while the current passes, and forced back again by a spring when it is stopped, thus setting in action the mechanism of the alarm; or in some cases there is a simple contrivance for causing a rapid flow and stoppage of the electricity, so that the bar is alternately attracted by the magnet and released by the spring, and this motion rings the bell as long as it is continued. The bell is always rung to give notice that a message is about to be sent, and at the station where it rings, the bell at the former station is rung in return, to show that they are prepared to receive the message: which is then spelt, letter after letter, by moving the handles into the proper positions, and as it is being sent, the eye is kept on the dials, certain single signs are made and recognised, which will communicate any reply from the station to which the message is being sent, such as “repeat,” or “not understood.” The wires which convey the electricity are made of galvanised iron (iron coated with zinc), and as they must be kept from all communication with the earth by some substance incapable of conducting it, they are therefore stretched between wooden poles (fig. 250), and rest upon sockets or supports of glass or glazed earthenware, which are both substances incapable of conducting the electricity to the earth (fig. 251), and in order that these may be quite dry, an inverted cup of metal, glass, or earthenware is placed over it, or the whole is blown or moulded in one piece. If the support for the wires were not kept from the rain, the wet would form a conducting surface, and allow the electricity to escape into the earth.

The Telegraph Alphabet, in the two-needle instrument, now not generally used in England, is given below.

TWO-NEEDLE ALPHABET.

In the single needle instrument the letters are indicated by right and left vibrations, from A one right, to B one right and left, and so on, increasing to Z. This mode is now generally used.

The manner in which the current passes is shown by the following illustrations (figs. 252, 253).

For the sake of clearness, the diagram has been drawn with simple lines only. In the real needle-machine the construction is much more complicated; perspective drawings of it may be seen in Lardner’s “Electric Telegraph,” and numerous other works. In fig. 1, B is a single cell of a battery containing a plate of copper, C, and a plate of zinc, Z, immersed in sulphuric acid and water. H is the handle of the instrument, turning from left to right, and vice versâ, like the handle of a door, consisting of two pieces of brass insulated from each other by being inserted in an axis of ivory. To the ends of the two pieces of brass are fixed the wires, CW and ZW, leading from the copper and zinc ends of the cell respectively. Fixed on each side of the handle are two plates of metal, which may be called LP, the left plate, and RP, the right plate. They are connected with the needle wire, NW, which passes before and behind the magnetized needle, N, suspended perpendicularly on its axis, with its north pole upwards. As long as the wires, CW and ZW, remain insulated from each other, no current passes from the cell; but as soon as the handle, H, is turned, so that the copper end touches the left plate (fig. 2), and the zinc end touches the right, communication is established between the plates of the cell, and the current commencing at the copper passes along CW, the top half of H, into LP, along N W, travelling up before and down behind the needle, causing it to deflect to the observer’s left, according to the rule given above. Reaching RP, it passes downwards to the cell to Z, and so on to C, continuing its travels and keeping the needle deflected as long as the handle remains in contact with the plates. If it is required to deflect the needle to the right, the handle is turned to the right, bringing its copper end in contact with the right plate, causing the current to travel in the opposite direction. By following the current from the copper to the zinc, as indicated by the arrows in fig. 3, it will be seen that it now travels up behind and down before the needle, deflecting it to the observer’s right. Thus, by causing a current of voltaic electricity to pass alternately up before and down behind, and up behind and down before, the needle is moved to the left or the right at will. The way in which the current is made to act on a distant needle is now simple. The following figure (fig. 253) shows the arrangement. The left portion of the figure represents an instrument at London, that on the right an instrument at York. The needle-wire, instead of being continued directly to the zinc plate of the battery, passes away from the needle over poles to York, where it joins an instrument similar in all respects to that at London. It passes similarly before and behind a magnetized needle, joining the right plate of the instrument. As long as the two plates are unconnected, no current can pass. The current is therefore completed by a contrivance which may be represented by the semicircular piece of metal, K. In practice the two plates or springs, which, when not in use, are always pressed against the connector, K, which is a cross-piece on the top of the handle, keeping the London needle in circuit with the York battery, and vice versâ. As soon as London uses his handle, it presses the spring-plate, and puts his needle out of the York circuit, the current he sets up sending York needle to the right or left, as the case maybe. The second wire connecting the left York plate with the right London plate is, it will be seen, not carried along like the first wire. Use is made in this case of the conducting power of the earth itself, plates from the wires being buried many feet below the surface at London and York. When London wishes to speak to York, he first signifies his intention of so doing by ringing York’s alarum. This he effects by sending a current through an electro-magnet placed above York’s instrument. The armature is attracted, and frees the detent of the alarum, setting it ringing until York signals ready. London then stops the bell, and commences his message. By following the direction of the current, when the handle is turned to the left, as in fig. 4 [within fig. 253], it will be readily seen how this is effected: commencing with London’s copper, LC, it passes up before and down behind London’s needle, flowing along the wire between the two cities to York’s needle, up before and down behind which it travels, sending it also to the left. It then passes to York’s right plate, through the connector to the left plate, and so on to earth at York, coming to the surface again at London, passing through London’s right plate and through the lower part of the handle to the zinc of the battery. The reverse current may be easily followed. Any number of instruments with similar needles may be interposed along the course of the wire. When the operator wishes to speak to any particular one, he rings all the bells for attention, and then signals Derby or Nottingham, as the case may be. They all then throw their instruments out of current except the one required. The mode by which the needle movements are converted into language is simple. A is signalled by causing the needle to vibrate once to the right, B once right and once left, C once right and twice left; and so on, as arranged.

The following is the alphabet (with numbers) once in use on the South-Eastern Railway for the double-needle instrument. The table is taken from Mr. Walker’s translation of De la Rive’s work on Electricity and Magnetism.

A is signified by two movements of left needle to left. B ” by three ” ” ” C (and fig. 1) by two ” ” right first, then left. D (and fig. 2) by two ” ” left first, then right. E (and fig. 3) by one ” ” to the right. F by two ” ” ” G by three ” ” ” H (and fig. 4) by one ” right needle to the left. I by two ” ” ” J (same as G). K by three ” ” ” L (and fig. 5) by two ” ” right and left. M (and fig. 6) by two ” ” left and right. N (and fig. 7) by one ” ” to the right. O by two ” ” ” P by three ” ” ” Q (same as K). R (and fig. 8) by one parallel movement of lower points, both needles to the left. S by two ” ” ” T by three ” ” ” U (and fig. 9) by two ” ” first right, then left. V (and fig. 0) by two ” ” first left, then right. W by one movement of both needles (lower points) to right. X by two ” ” ” ” Y by three ” ” ” ” Z (same as S) or specially.

The Morse system of telegraphy was first brought out in 1844, and was worked by means of a Voltaic battery, an electro-magnet being used at the receiving station. This magnet attracted an “armature,” and by it dots or lines are marked on a moving paper band by a point at the other end of the wire, on the register in which the paper is carried by rollers which move out by clockwork. The lever being “tapped” down in fast or slow pressures will give a corresponding series of dots or lines (according as the pressure is long or short) upon the moving strip of paper at the receiving station. Three taps will give C, one tap and a pause will make A. The dots are “taps” on the key, the lines brief “rests” on it, as will be seen from the alphabet below, which is given as a specimen.

MORSE ALPHABET.

A .- B -... C .. . D -.. E . F .-. G --. H .... I .. J -.-. K -.- L - M -- N -. O . . P ..... Q ..-. R . .. S ... T - U ..- V ...- W .-- X .-.. Y .. .. Z ... .

NUMBERS.

1 .--. 2 ..-.. 3 ...-. 4 ....- 5 --- 6 ...... 7 --.. 8 -.... 9 -..- 0 ___

The various stops are also indicated in the same manner by combinations of dots and lines.

The Atlantic telegraph cables and similar enclosed wires between other countries are too well known to need detailed description. There is a great variety of telegraphic instruments. The dial, and other arrangements, are very common, and the Wheatstone Key instrument is supplied to private firms as being the most handy. It requires but a very short apprenticeship, and any person who is handy can easily learn to work it in a few minutes. The apparatus consists of a dial upon which the letters of the alphabet are printed, each letter being supplied with a key or stop. A pointer is placed in the centre, as in the wheel barometer, and there is a handle beneath. In front, upon a sloping board, is another dial plate and pointer; thus we have the receiver and transmitter before us in a very small space.

When it is necessary to work the instrument a bell is rung by turning the handle rapidly. To speak by the instrument it is necessary to keep turning the handle with the right hand while the fingers of the left are employed in pressing down in as rapid succession as practice will permit the keys corresponding to the letters on the dial while the handle is kept turning. When a word is completed the operator must stop at the + at the top, and then begin again, stopping after each word. When all is said, a couple of rapid turns of the dial will signify that you have ended.

There are many other systems of telegraph, but all are dependent upon the same principles. The accompanying illustrations (figs. 254, 255) show a dial telegraph of a simple kind, which almost explains itself.

The first figure is the receiver, on which is a pointer fixed to a dial-plate having the letters of the alphabet inscribed around it. When the manipulator is being worked the dart points to the letters in succession of the words used, and they are separately spelt. The manipulator (fig. 255), by closing and opening the circuit, works the needle.

In the manipulator we have a wheel with an index point fixed above it. In this wheel are thirteen teeth, with the openings between them filled with ivory. The axis of the wheel is in contact with the wire from the positive pole, p, and a spring attached to the wire or by the binding-screw, t, presses against the circumference of the wheel, and completes the circuit. When the wheel is placed so that the arrow point is above the +, the needle of the receiver is also at +. By turning the wheel to bring the needle to A, the spring on the circumference is passed from an ivory “tooth” to a “metal” one; the circuit is closed, the point of the receiver also turns to A, and so on through the word by successive closing and breaking of the circuit.

As there are a great many other applications of electricity of which we have to treat,—the Electric Light, and Mr. Edison’s other inventions,—our space will not permit a much more detailed account of the telegraph, but there are some incidents connected with its progress which it would be as well to mention.

Alexander Bain, about 1840, attempted to produce a printing telegraph, and in 1846 he actually accomplished a registering apparatus, which was an application of the principles of Dyar and Davy. But although Bain’s system was good, Morse had the advantage of possession in the United States, where it was tried, and Bain went out of fashion. Bain’s system was, in fact, the present chemical “automatic” telegraph, which has been perfected for rapid transmission.

Bakewell’s instrument, which has been improved upon by later electricians, is termed the fac-simile telegraph. The message to be sent is written with a pen which has been dipped in varnish (for ink), and the characters are inscribed upon prepared tinfoil. The message is then put upon a cylinder covered with prepared paper, and has a pointer attached. There is a precisely similar cylinder at the receiving station. When the cylinders are simultaneously set going, the point at one will trace a spiral line as the first (transmitting) point passes round its cylinder. However, as the latter “stylus” meets the varnish letters a break occurs, and these spaces are exactly reproduced as blanks at the other end, and the form of the letters can be seen. Coselli, in his adaptation, caused dark letters to be registered on a white ground, and thus simplified matters. Since then we have had printing telegraphs, and dials, and writing machines, one of which will be described presently.

Submarine telegraphs were, it is said, first suggested by Salvá in 1797, and Wheatstone, in 1840, declared that it was quite possible to connect England and France by wire. Morse and Calt experimented with submarine cables in America, and Lieutenant Siemens first applied gutta-percha to the wires as an insulator in the Prussian line of telegraph across the Rhine. The English laid a wire between Dover and Calais, which was broken, but successfully relaid. And so on, till in 1857 the great project of the Atlantic cable was broached. We give illustrations of the cables; the circumstances connected with the laying of which, and the enthusiasm over the successful accomplishment of the task, must be in the memory of all. The readings of the messages were shown by delicate galvanometers, the beam of light being reflected from a mirror. This cable was lost, and in 1862 Mr. Field came over to urge the importance of the submarine cable between this country and America. The cable was shipped on the Great Eastern in 1865, and was 2,186 miles long. It consisted of seven copper wires twisted, and covered with gutta-percha. The outside coating consists of ten iron wires surrounded by manilla yarn. But this cable broke, and a third was made and laid in 1866. The old cable was then recovered and spliced. There are some two hundred cables now in existence, the last being the Cape cable, laid when the Boer War was engaging our attention. The transmitting apparatus of Mr. Varley and Sir W. Thomson has greatly accelerated the rapidity of messages, and Thomson’s syphon recorder farther increased the speed.

The following description of a new system is from Scribner’s Magazine for 1880:—

“NEW TELEGRAPHIC SYSTEM.

“A new system of sending and receiving electrical impulses over an insulated wire has recently been brought into successful operation, that seems to promise not only a radical change in the present methods of telegraphing, but a material gain in the speed and cost of sending messages by wire. It is founded on a union of the so-called “automatic” and “chemical” systems of telegraphy. The first of these employs a strip of paper having, by some mechanical means, a series of small holes punched in it, the design being to pass the perforated strip under a needle, or stylus, in electrical connection with the line. This stylus, on passing over the paper, opens the circuit, but in passing one of the holes, drops through and closes it,—this alternate making and breaking of the circuit transmitting the message. The chemical telegraph records any electrical impulses sent over a line by staining a strip of prepared paper passing under it. This is founded on the fact that electricity has the power of decomposing certain chemicals, and if paper is soaked in these chemicals and submitted to the action of electricity, it will be discoloured wherever the current passes. While both of these systems have been used, neither has been able to compete with the more simple Morse key and sounder, and it has remained for the new system to bring them to a position where they may come into general use. The new system is a modification and combination of the automatic and chemical systems, the transmitting being performed by means of a perforated strip of paper, and the receiving of the message being recorded by the discolouration of chemically prepared paper. The process is entirely mechanical and chemical, the telegraph operator having no direct control over the message, either by sight, sound, or touch. The written message is sent to the operating-room, and given to the person using the perforating machine. This consists of a small key-board, with black and white keys, each marked with a letter or sign, and an ingenious system of levers, operated by the keys, for punching small holes in a ribbon of paper moving past the side of the machine. The machine stands upon a small table, and under it is a treadle for giving motion to the feeding apparatus for supplying the paper to the machine. The operator moves the treadle with his feet, and at the same time touches each key to spell out the message. In a very few seconds the message is imprinted on the ribbon in the form of a double row of small perforations, each group of two holes representing a dash, and each single hole a dot, as in the Morse alphabet. Each letter is separated from the next by a longer dash, and each word by a still longer dash, and each sentence by a dash of indefinite length. This spacing of the letters is performed automatically, the spacing of words and sentences is performed by the operator. The perforated slip containing the message is then sent to the transmitting machine. This consists essentially of a metallic wheel, divided into two sections by means of a thin insulation of hard rubber. One section of the wheel is connected with the positive pole of the battery, and the other section with the negative pole. A pair of fine metallic brushes, both of which are connected directly with the line, are suspended above the wheel, and are arranged so as to press lightly upon the latter, when desired. When resting on the wheel the circuit is closed, and when raised above it the circuit is broken. The perforated strip is, by a simple piece of mechanism, made to pass over the face of this wheel and under the brushes. While the paper is passing, both brushes are raised from the wheel, and slide over the paper, and the circuit is broken. On passing a hole, one of the brushes drops through and closes the circuit for an instant. On passing two or more holes, arranged in a series close together, the brush closes the circuit for a shorter or longer time, according to the number of holes, and as the perforations on the paper are arranged in two rows, alternating from one to the other, the brushes are used alternately, and the polarity of the current is continually changed with every impulse sent over the line. No special skill is required in sending a message, as the operator has only to put the perforated strip in the machine and turn a hand-crank, to cause it to pass rapidly under the brushes, and with a little practice, a young girl can send messages at the rate of one thousand words a minute, with absolute precision. The receiving apparatus consists essentially of a simple piece of mechanism for causing a strip of chemically prepared paper to pass rapidly under two small needles that are connected with the line. As the paper passes the needles, the electricity sent over the line from the transmitting machine seeks the earth through the wet paper and the machine, and in passing discolours the paper, each stain representing a dot or dash, and the message is printed on the paper in a double row of marks at the same speed with which it was dispatched. In practice, a Morse key and sounder is placed at each end of the line, and on sending a message the transmitting operator calls the receiving station, and when the operator at the distant end replies, both turn the cranks in their machine swiftly, and the message is sent and received at an average speed of one thousand words a minute. The message received is given to a person using a type-writer, and at once translated into print and sent out by the messenger boy. It is found in practice that two operators, one at each end of a single wire of indefinite length, can keep fifteen operators fully employed in preparing the messages, and fifteen girls busy in translating and printing the messages for delivery. The system is of American origin.”

Of the hundred and one uses to which electric wires are now appropriated—of the alarms, fire-calls, clocks, etc.—we need not speak. We must pass on to the Writing Machine (fig. 258) before we make mention of Mr. Edison’s inventions.

The Writing Machine is as remarkable for the simplicity of its mechanism as for the facility and ease with which it can be used. It was invented by Remington, the American, whose name is so universally known in connection with a repeating rifle. He makes these writing machines in his own factory, where he associates them with rifles and sewing machines—implements for war and peace.

The appearance of the Writing Machine may be easily perceived from the illustration (fig. 258), which is drawn to scale one-fourth of the actual size. It comprises a key-board, upon which there are forty-four keys or stops, including numbers from 2 to 9, the i and o of the alphabet serving for numbers 1 and 0, and all the letters of the alphabet arranged in the manner most convenient for manipulation. There are also the various accents and stops, with note of interrogation, etc. The flat ruler at the base of the key-board is struck when it is necessary to separate one word from another.

In the interior of the apparatus every letter is attached to a small hammer, and corresponds to the pressure bestowed upon the notes, which are disposed in a circle. If A, for example, be touched upon the key-board, the hammer will bring A to the centre of the circle, and so every letter of the word will be, by such action, brought to the centre of the circle in succession. The paper upon which the letter is printed is wound upon a cylinder mounted upon a slide, as seen in the upper portion of the illustration.

When the letter is pressed down on the key-board the corresponding hammer strikes against the cylinder, between which and the hammer is a ribbon prepared with a special ink. The letter being in relief like ordinary type is impressed upon the paper. The slide upon which the paper is mounted is so arranged as to move from right to left exactly a letter-breadth after each impression. Thus as every hammer strikes at the same spot a regular succession of letters are printed off, the paper moving with regularity. When the line is filled—that is, when the paper has moved across the cylinder—a bell rings, and a handle is moved by the operator who is thus warned. The lever moved brings the slide back again, and a new plain surface is ready to commence upon the cylinder moving upwards at the same time, and displaying the printed line.

In operating both hands may be employed, but between each word care should be taken to press down the flat board at the base of the key-board, which has the effect of leaving a space upon the paper. Immediately the sound of the warning bell is heard the lever at the right-hand side must be lowered. The word can be finished in the line following if it be not concluded, the hyphen button being pressed to indicate the continuation.

The paper used must not exceed the width of the cylinder, but it may be of any less width, and a post-card or any small sheet of paper may be substituted. If the width be thus limited the length may be indefinite, and a very long line of paper may be used if desirable. The cylinder being made of gutta-percha offers a soft surface to the impression of the hammer, and causes the letter to assume greater distinctness.

The inked ribbon which passes underneath the paper is so arranged that no two successive letters strike it on the same place. It moves from an ink reservoir on the right to another on the opposite side, and it can be made to return beneath the paper, thus keeping up the supply. The impression being made in copying ink, the message or letter when finished can easily be reproduced in an ordinary press. The characters are all “capitals.”

At first it may be found a slow means of writing, and the manipulator may imagine he can do better without it. But if the author be certain of what he intends to say, after a little practice at the instrument, and when he becomes accustomed to the positions of the various letters, etc., the rate at which words can be printed off will far exceed that at which even rapid writers can work. A young English lady after some days’ practice was able to write as many as ninety words a minute with this machine—a rate more than double the average writing rate of penmanship. When such a rate or an approximation to it can be attained, those who are quick in their ideas will find the machine a great saving of time, and for any one afflicted with “writer’s cramp” the gain must be enormous. We need not insist upon the advantages the adaptation of the apparatus would confer upon editors and readers of MSS. too often badly written, and to compositors the invention is a great boon.

Finally, the working of the machine could be entrusted to the blind, and by teaching them the form of letters which could be raised upon the key-board, those so sadly afflicted could write with facility. Some methods for teaching the blind to manipulate and to read from the impressions of the hammers on the paper have already been tried with success.

The Electric Pen, an invention of the fertile brain of Mr. Edison, is shown in fig. 259. The “writing” consists of a series of little holes close together, made by a fine steel point like a put-crayon. This point is thrust in and out with great rapidity, and passes quickly over the paper. If the characters cannot be formed so quickly as with an ordinary pen, the writing is very distinct.

The alternative movement is given to the pen by an electric motor at once simple and ingenious, which is placed on the top of the penholder. The general appearance of the apparatus will be understood from the cut on next page.

The point is the termination of a wire which traverses the penholder, and the upper extremity of which catches on the motor by an eccentric. This eccentric has three teeth or cogs, and it makes sixty revolutions a second, thus producing one hundred and eighty beats in that time. The axle carries a plate of soft iron, which acts like the armature of an electro-magnet, before which it turns with great rapidity, the current being interrupted twice in every revolution by the commutator. The current which moves this little apparatus is furnished by a pile of two elements in bichromate of potash, according to Mr. Edison’s arrangement, which is considered very successful. Carbon and zinc are employed, and when ready for action the battery assumes the appearance of the cells in the illustration. When the operator wishes to discontinue writing, he simply raises the stem which has the electrodes attached to it, and the elements are thus preserved for a future time.

Under these circumstances the battery could be made to last several days without any renewal of the liquid, and the plates will last for weeks. Thus a very simple arrangement is at our disposal. Let us see what use can be made of it.

When we use the electric pen we obtain a great number of small holes close to each other. Such hand-writing is not easy to decipher by mere inspection like ordinary writing. By holding it up to the light it is more easy to read, but in both instances reading is not easy, nor does it come by nature as Dogberry declares. But if we consider the paper as a “negative,” we may obtain a number of positive proofs or copies of the writing. To obtain these successfully we must use a press, as shown in the accompanying illustration (fig. 260).

The writing, or negative, is placed upon the cover to the left, where it is firmly fastened. Upon the body of the press a sheet of white paper is placed, and when the lid is shut down the negative comes in contact with the paper. By means of a roller, represented in the box, the writing is blackened,—the ink penetrates into all the holes which are upon the paper,—and after the manner of a stencil plate the impression will be found upon the paper when the cover is removed. The writing will have a curious effect, but practice will speedily remove all deficiencies. The same negative will serve for a great many impressions, quite a thousand having been taken from one. By people accustomed to such work as many as six proofs a minute may be obtained. Of course a little practice will be necessary in this, as in every other case, before a correct or rapid result can be obtained, but there is no difficulty in the practice.

There are two or three other applications of electricity which we must refer to; such as the electric stamp, of which we give an illustration, and a curious method of stopping a horse by electricity. The electric stamp might be very advantageously employed in our post offices to obliterate the “Queen’s Head.” The description, with illustration of this apparatus, is annexed. (See fig. 261.)

At the lower end of the apparatus is a thin platinum wire, so arranged as to form either a design or an initial; by this the postage stamp can be defaced. The stamp being put in communication with the pile, the circuit is closed by the pressure of the finger, as shown in the illustration. The platinum grows heated and carbonises the paper, and thus proves itself an ineffaceable stamp.

This apparatus may easily be used, not only by the post office authorities, but by every one who is obliged to deface a certain number of stamps every day, and wishes to do so rapidly and without possibility of error.

An ingenious, if scarcely necessary arrangement for conquering restive horses, and frightening them into submission, is shown in the illustration (fig. 262). Many means have been tried to stop or conquer a restive horse, but the most efficacious has been designed by M. Defoy; and the director of the Paris General Omnibus Company has experimented successfully, as we are informed, with the arrangement we are about to describe. A small magneto-electric machine is contained in a box beside the driver, within easy and convenient reach of his hand. The reins contain a wire, one end of which terminates in the horse’s bit, and the other in the electro-magnetic apparatus. When the electro-magnet is put in action an electric current is generated, which gives the horse a shock in the mouth, and so astonishes him that he suddenly stops in his course. If the operator have the humanity and good sense to unite kindness to the abrupt application of the electricity,—which in our opinion should be only used as a last resource,—no doubt some excellent results may be obtained even with vicious animals.

M. Bella, the Director of the Omnibus Company, has reported that the apparatus was tried in his presence and found very successful, and quite easy of application; and that even the most unruly animals have been subjected by it. On one occasion a most restive animal was thus treated on the way to the forge. He had a tremendous objection to be shod, and made no secret of his dislike. But a gentle application of the electric current put quite an opposite complexion upon the matter, and after a few minutes the animal permitted himself to be patted and caressed, and even allowed the smith to feel his legs and inspect his feet without making any objection whatever. His shoes were taken off, and the horse was re-shod without any of the dangerous demonstrations hitherto indulged in by the animal.

We may quote another instance of the efficacy of this method, which is reported from Paris by M. Camille.

“Many experiments have been made upon horses which had been most difficult to shoe, and in each case we have succeeded when the electric apparatus has been put in requisition. One horse, in particular, nothing could subdue. He kicked and bit and jumped about in such a manner as to render all approach impossible. We had recourse at length to M. Defoy’s apparatus, and after the first application, and without any great difficulty, we were able to raise the animal’s feet; but after a second lesson we were permitted to shoe him without his offering the slightest resistance. He was completely subdued.”

M. Defoy recently made the experiment with a very dangerous animal, which he stopped instantaneously in full gallop (see fig. 262). It may be remarked that the application of the current is not sufficiently strong to stop the horse too suddenly. It merely causes a very unpleasant sensation—he is not stupefied nor galvanized by the electricity. The narrator has felt the shock applied without inconvenience, and the conclusion arrived at is, that this method of employing electricity is far superior to the violent and inhuman treatment so often employed to break horses, which renders them subsequently sulky and vindictive.

M. Defoy has completed an electric bit and an electric stick quite as ingenious as the electric rein. The modus operandi is simple and effective, the wires being insulated by leather, and terminating at the extremities of the stick. The current is induced, as before, by a small magneto-electric machine.

FOOTNOTES:

[15] Encly. Metrop.

[16] “Treatise on Electricity and Magnetism.”

[17] Sabine: “The Electric Telegraph.”

Spotted a typo or a problem in this chapter? Tell us

XXI. MAGNETISM

THE LOADSTONE—MAGNETIC CURVES—THE MAGNETIC NEEDLE—THE MARINER’S COMPASS—MAGNETO-ELECTRICITY.

We have already mentioned some of the properties of the loadstone or magnet; but as we are now about to enter more fully into the considerations of its attributes and of the compass, etc., we will add some further interesting particulars.

Ancient writers (Pliny, Homer, and Aristotle) mentioned the existence of the magnet, and Humboldt refers to the knowledge of it possessed by the ancients. Pliny says “the magnet-stone is found in Cantabria,” and we have heard of the loadstones that are supposed to support Mahomet’s coffin at Medina. The origin of this fable was (probably) owing to the order given by Ptolemy to his architect, Dinochares. Ptolemy wished the roof of a temple at Alexandria to be roofed with the magnet-stone, so that the own image of his sister, Arsinoe, should remain suspended therein. But the death of the king and his architect prevented the project from being carried out.

The name “magnet” is said to have been derived from a shepherd named MAGNES, who, when tending his flock on Mount Ida, found that his iron crook was attracted to a certain stone; and six hundred years before the Christian era Thales wrote respecting amber and the magnet; and because they attracted various substances, he supposed they possessed life and power. They were the germs of the science now so developed in their applications, and whose full powers we are scarcely yet acquainted with.

We may remark that other bodies besides iron and steel are capable of magnetization; nickel and cobalt have the like property. Magnetism, properly so called, treats of certain bodies known as MAGNETS, describes the properties they possess, and the influence of magnetic force upon other substances. Electricity and magnetism are always associated, but practically the force is the same, electricity being the current or motive power, so to speak; and it is to Faraday that the world is indebted for the discovery of magneto-electricity.

Epinus’ theory of magnetism was that all bodies possessed a substance he termed magnetic fluid, the particles of which repelled each other. But while supposed to repel each other, they attracted particles in other bodies. Thus they attracted iron. Coulomb asserted that there were two fluids—a north and south fluid. Ampère’s theory was that magnetic bodies are made up of molecules, round which currents are always circulating in all directions when non-magnetized, but when magnetized the currents all flow in the same direction. The space through which a magnet diffuses its influence was called by Faraday the Magnetic Field. The lines of magnetic force will be understood from the accompanying illustration (fig. 263). If we cover a magnet with a paper and scatter iron filings over it, we shall see the manner in which the filings arrange themselves. They radiate in curves from the poles of the magnet, and are dependent upon its form. If it be a straight bar magnet, evenly magnetized, they will turn inward in oval curves.

The manner of magnetization has already been mentioned, but here we will give further illustrations of the method of magnetization. Four magnets are used, two being placed with their opposite poles apart, and upon them is placed the bar of which a magnet is to be made. Two other magnets separated by a piece of wood are then brought near, and subsequently drawn from the centre to the ends of the bar. This is the separated touch system; the double touch of Mitchell is completed by moving the upper two magnets from end to end backwards and forwards, and finally lifting them away from the centre.

A magnet, then, is a bar of steel endowed with certain properties, such as attracting iron, etc.; and electro-magnetism is the term applied to the production of magnetism by means of electricity, the medium being the electro-magnet. To understand the science it will be necessary to mention Ampère’s theory of magnetism.

It was Œrsted who observed that when a magnet is placed within reach of an electric current and free to move, it sets itself at right angles to the direction of the current; and Ampère defined the law already referred to when treating of the electric current,—viz., “that if a person be imagined as placed in the wire so that the current shall pass through him from feet to head, if he turn his face toward the magnetic needle the north pole will always be deflected to his left-hand side.” When the current is passed above the needle from south to north poles, the deflection is to the west; when from north to south the deflection is east. When the current is below the needle the contrary is the case. Ampère decided that currents circulating in the same direction attracted each other, and when running in opposite ways they repelled each other. He supposed currents to circulate within all magnetic substances, and then—that is, when the body is magnetized—these currents flow in planes parallel to each other, and the material which offers the least resistance to the circulation of these currents becomes the most magnetic.

The earth being supposed to be an immense magnet has currents circulating through it in a direction from east to west; and having the property or power of turning a magnetized bar in a direction similar to that in which the bar would be turned by a magnet, the earth is considered a magnetic mass. This influence is due to what is called “terrestrial magnetism.” If we suspend a bar by a thread it will point in no particular direction, but may be turned towards any side we please. But when once the needle is magnetized it will point north and south; or, as we say (but not correctly), the north pole of the magnet points to the north of the globe. It is really the south pole that points to the north, and the north pole of the magnet points south, as can be proved by suspending the bar over another magnetized bar. So if the earth be considered a magnet our English terms are inconsistent with our theories. Continental writers are more correct.

The line of the magnetic needle’s direction, which differs in different places, is called the magnetic meridian, and the amount of its divergence from the astronomical meridian is termed its declination or variation. When the amount of this variation is known it is allowed for, and the needle can be considered as pointing due north and south.

But the needle does not assume a position perfectly parallel to the horizon. It dips down in different hemispheres. As we approach the north pole the dip or inclination will become greater, and the same effect is observable at the south pole. Again, there are certain places on the earth where the attraction is so evenly balanced that the needle is perfectly horizontal. The line uniting these places is the magnetic equator. This does not coincide with the earth’s equator any more than the magnetic poles coincide with the geographical poles of the earth.

The declination of the needle varies from the meridian of Greenwich at different times. If we travel to the west the variation increases westerly, and is greatest in the Atlantic. It then decreases; the needle points due north in North America. Going still forward the variation becomes easterly, increases, and decreases to nothing in Eastern Russia. Thence the variations are westerly. Columbus discovered the variation of the compass needle in September 1493. In places where the needle is due north and south the lines drawn through them are termed lines of no variation.

The variation, however, is not always the same in the same place. In the year 1580, in London, for instance, the variation was 11° 11´ E. A little more than one hundred years later London was on the line of no variation, and now the tendency is westerly. On the other hand, there are places where there is no deviation, and Sir John Herschell says that West India property has been saved from litigation in consequence of the invariability of magnetic declination there, for all surveys were made by the compass. Lines of equal variation are called isogonial; those of equal dip or inclination, isoclinical; and those of equal intensity, isodynamical.

As we have said, the magnetic elements are not always the same, and the variations of the compass are daily and annually observed with certain instruments. What are termed secular variations take place at long intervals, as the following table will show:—

In 1576 the angle of declination in England was 11° 15´ East. 1622 ” ” 6° 12´ ” 1660 ” ” 0° ” ” 1730 ” ” 13° West. 1760 ” ” 19° 30´ ” 1800 ” ” 24° 36´ ” 1818 ” ” 24° 41´ ” 1850 ” ” 22° 29´ ” 1870 ” ” 19° 55´ ” 1873 ” ” 19° 58´ ” 1879 ” ” 19° 7´ ”

In the year 1818 therefore the maximum declination was reached in London. In Paris the maximum was arrived at in 1814, and was 22° 34´. The rate of decrease is about 8´ a year, but varies in different periods, as may be seen. The discovery of the fact that an annual variation took place in the angle of declination, is attributable to Cassini, and the diurnal variation was discovered by Graham in 1722. From 8 o’clock in the morning, when the needle is pointing a little to the east of its “mean position,” it turns towards the west until 1 p.m. It then returns towards the east again, and passing westerly again between midnight and three o’clock a.m., settles down till eight a.m., when it begins afresh. This variation does not apply to all places.

Magnetic inclination is besides subject to changes. There are also variations of magnetic force which occur at very irregular periods, and cannot be said to follow any laws. These disturbances are called Magnetic Storms, of which the Aurora Borealis is one result.

Professor Faraday in his memorable experiments divided a long list of different substances into para-magnetic and dia-magnetic bodies. He classed them under these two heads, according as they took up a certain position parallel or perpendicular to the axial or equatorial line. This definition of “dia-magnetic” was “a body through which the lines of magnetic force are passing, and which does not by their action assume the usual magnetic state of iron or loadstone.” He concluded that all bodies were magnetic, and by suspending a great number of various substances he found they placed themselves axially,—that is, lying between the poles of the magnet, or equatorially,—viz., at right angles to that line. If the magnets be suspended at each side the same bodies will assume a position with their longest diameters between the poles, while others will be repelled by the magnets even if the poles be reversed. So those bodies which are attracted and lie in the axial line are termed para-magnetic; those repelled into the equatorial line are termed dia-magnetic. In the “Proceedings of the Royal Society for 1846,” Faraday’s account of the various experiments can be studied in detail. We can only give a brief resumé of them here; and he showed that the motions displayed by dia-magnetic bodies in a magnetic field are all reducible to one simple law—viz., that the particles of the dia-magnetic tend to move into the positions of the weakest magnetic force.

He experimented upon a large number of bodies and gases; he tested crystals, metals, liquids, and solids, and proved in whatever state a body might be in the effect was the same; whether simple or compound, it made no difference. Of course in a compound the preponderance of the dia-magnetic or para-magnetic property would influence the result, and the medium in which the body operated on was placed, was a condition in the experiment. He proved that if a body be suspended in a medium or surrounded by a medium whose power either way is stronger than the body, that body is para-magnetic or dia-magnetic, according as it is surrounded by a medium whose power is weaker or stronger than the body itself. The arrangement of the bodies is as follows, from the para-magnetic to the dia-magnetic, bismuth being the most dia-magnetic of all:—

PARA-MAGNETIC METALS.

Iron. Nickel. Cobalt. Manganese. Chromium. Cerium. Titanium. Palladium. Platinum. Osmium.

DIA-MAGNETIC.

Bismuth. Antimony. Zinc. Tin. Cadmium. Sodium. Mercury. Lead. Silver. Copper. Gold. Arsenic. Uranium. Rhodium. Iridium, etc.

Common air was also discovered to have a magnetic action, and hot air is more dia-magnetic than cold. Oxygen is as para-magnetic in the air as iron is on the earth, and this, it was considered, may give rise to magnetic storms, and account for the declination of the needle.

We may now proceed to consider the Mariner’s Compass. The compass, or the mariner’s compass, is so common that it is scarcely necessary to give a long description of it. Its history is unknown. The Chinese seem to have been aware of its usefulness long before the western nations adopted it. It was about the time of the Crusades that it was brought into western prominence, but was not generally known till the thirteenth century. Chinese writings ascribe to the compass a great antiquity; they maintain that it was discovered two thousand five hundred years before the Christian Era, and used for travelling on land. But, according to other accounts, it was not used at sea till the year 300 A.D.

The Chinese put the south first when speaking of the points of the compass, and in the Chinese empire and Thibet west goes likewise before east. So the imperial edifices in China face the south, and the needle, in their expression, points south and north—not as we say, north and south. The antiquity of the compass may be inferred from the recorded fact in Chinese chronicles, written in the second century before the Christian Era, that nine hundred years previously to the date of the chronicle the Emperor gave magnetic cars to certain ambassadors to guide them home in safety. These cars were fitted with a magnetic needle which communicated with a figure. Its outstretched hand and finger followed the compass-direction, and pointed out the way.

The Chinese subsequently (in the twelfth century) suspended the needle by a thread, and it is said their philosophers at that time noticed the variation of the needle. But Columbus first, in 1492, and Cabot, in 1540, certainly remarked it in Europe. It is to Marco Polo that we are indebted for the direct introduction of the needle into Europe, although it probably had been in use in the Levant previously, for we have seen a quotation by an Arab writer, who, in 1242, described the needle as being used at that time on his voyage from Tripoli in Syria to Alexandria, two years previously.

Friar Bacon possessed a loadstone, and there are many instances in which it is referred to in ancient writings. The inventor of the compass we cannot trace, but no doubt exists as to its being of Chinese origin.

The ordinary compass is shown in the illustration herewith (fig. 265). It consists of a magnetized needle, suspended freely, and fixed to a circular card, which is divided and subdivided into thirty-two points, as in the cut. This compass is suspended upon gimbals to keep it in an upright position when the vessel rolls or plunges. The gimbals are concentric rings, the compass being fastened to the inner one, and keeps its position in all weathers. It is then enclosed in the binnacle, a glass receptacle. The card moves with the needle which points north. There is a dark line (lubber line) which indicates the ship’s course, and when sailing the steersman must keep that line opposite the compass direction-point which indicates the course. At night a lamp is lighted in the binnacle, and the card being transparent and the points opaque they are easily seen.

The magnetism of iron ships has a tendency to disturb the needle, and many suggestions have been made and discussed with a view to obviate this. To put the compass at the mast-head was one, to surround the compass with “counter-irritants” another. But the usual way is to “swing the ship,” and so adjust the compass. Swinging the ship means turning her round point by point, and marking the deflection of the needle with reference to a certain object. The amount of deflection at each point is read and noted, and subsequently taken into consideration when sailing.

The Azimuth Compass is a mariner’s compass fitted with brass uprights slit through the centre, through which the heavenly bodies may be seen. These are the sights. The card is divided into degrees and quarters. A fine wire is fixed upon one of the sights, and in the other slit is a prism to reflect the divisions of the card to the eye. The object—the azimuth distance of which it is desirable to know—is looked at through the slit, and bisected by the wire. The divisions of the scale are at the same time reflected, and the number read gives the azimuth distance required.

The compass has led us away slightly from our consideration of the electro-magnet, but we will now examine it and its effects as briefly as possible.

An electro-magnet is formed by wrapping a copper wire round a piece of soft iron shaped like a horse-shoe; the wire should be insulated with silk. If the wire be wound round the iron in the same direction, and a current be merely sent through the coil, it will be found that the horse-shoe iron is highly magnetic, but if the current be stopped the power is lost. Such magnets will carry weights much heavier than themselves, and by careful consideration of certain laws, and with reference to the number of coils and the strength of the current, these magnets will sustain a weight some thousands of times greater than their own weight.

If we cover a non-magnetic piece of iron with a wire coil, and taking a magnet turn it rapidly beneath the wire-bound iron, so that the magnetic poles approach each other alternately, an electrical current will be generated in the wire. The electro-magnetic machine is thus made; but although strong currents may be generated as a source of motive power it is a failure.

To Faraday our knowledge of magneto-electricity is due. “He knew” (says Professor Tyndall in his interesting work, “Faraday as a Discoverer”) “that under ordinary circumstances the presence of an electrified body was sufficient to excite by induction an unelectrified body. He knew that the wire which carried an electric current was an electrified body, and still all attempts had failed to make it excite in other wires a state similar to its own.”

But while he was making his experiments on the induction of electric currents he noticed that at the time the current was passing from the battery through the coils of wire that no motion was perceptible in the galvanometer. But when the circuit was opened, and when it was closed, there was a slight motion of the needle in the galvanometer, but in different directions. After consideration the philosopher came to the conclusion “that a battery current through one wire induced a similar current through the other, but for an instant only.”

Œrsted had already demonstrated that all magnetic effects were attributable to the attraction and repulsion of electric currents; and founding his views upon the theory of Ampère, Faraday came to the conclusion that electricity could be produced from magnetism, or that the electric current could be obtained from magnets. This he succeeded in doing. By inserting a steel magnet about half its length into a coil of wire, Faraday induced a current to pass through the wire in two directions. Thus he proceeded to solve all the mysteries of magneto-electricity, and stated that to produce currents it was only necessary to “cut appropriately the lines of magnetic force.”

The application of the magnet to the machines for electric lighting will be shown further on. Very powerful currents are obtained by the induction coil; but the currents would not be of practical service were it not for the apparatus called a Commutator, or key, which reverses the connection of the bobbins, and turns the current at every half revolution. Just as if a current were being sent across and back over a table, and when the current has reached the end, an instantaneous wheel round, or pivoting of the table, sends the current on, in continuation (but on the table all the time), because of the sudden change of its position. The back rush being on the table, the movement of the latter really makes the line continuous, and by quickly breaking and reversing the current in the commutator, the effect is gained in the machine.

Spotted a typo or a problem in this chapter? Tell us

Chapter XXII

SUNDRY ELECTRICAL APPLIANCES—MR. EDISON’S INVENTIONS—THE ELECTRIC LIGHT—THE GYROSCOPE—A NEW ELECTROPHORUS—ELECTRIC TOYS.

THE ELECTRO-MOTOGRAPH—although perhaps even yet scarcely developed—has already proved a very useful invention. The idea of it first occurred to Mr. Edison in 1873, when he was prosecuting some researches in chemical telegraphy. “One day,” says Mr. Fox, in his account of the invention, “as he sat pondering over his work, he happened to take in hand the metallic point through which, as it rested upon the paper, the current was wont to pass. When again he closed the circuit to let the current through the paper, he held the metallic point loosely, and unintentionally allowed it to rest upon the paper. Every time he moved the metallic strip on the paper the latter became wonderfully smooth. Edison was determined to find the reason of this, and he decided that the electricity very much lessened the friction of the metal on the paper. He made many experiments, and brought the subject before the Royal Society in 1874, but nothing came of the idea till 1876, when Edison was perfecting his musical telephone.

“The new appliance is, in fact, the same invention revived and now perfected by the original inventor, and brought to complete practical success under the title of the ‘electro-motograph.’ The action of the ‘electro-motograph’ depends on the fact, discovered during former experiments, and employed imperfectly in the musical telephone, that the friction of moving bodies varies in greater or less degree with their electrical condition. In the electro-motograph a cylinder made of prepared chalk, and saturated with a strong solution of caustic alkali, is set upon supports, so that it can be turned upon its axis. A strip of metal fastened to the mica diaphragm rests on the cylinder, and is pressed so firmly by its spring upon the cylinder that when it is turned by means of the handle the friction of the strip on the cylinder tends to pull the diaphragm out of shape, causing it to bulge inward as long as the cylinder is in motion. If now, while this motion of the cylinder is maintained, an electric current passes through the strip of metal, and then through the chalk cylinder to earth, the amount of this friction is varied or it is destroyed altogether, and the strip slides freely on the cylinder. This was the basis of the former invention. The release from friction by a change in electric condition in the first instrument failed simply from ignorance of some slight matters of detail, that in the electro-motograph are corrected and made practical. In the musical telephone the releasing of the frictional resistance by electric action caused the sounding-board of a guitar to vibrate, and thus set up sonorous vibrations. In the electro-motograph the mica disc takes the place of the guitar, and, by the improved construction of the apparatus, intricate and complex vibrations, such as are produced in speaking, are reproduced in their original or even in greater volume. When the apparatus is at rest the diaphragm is motionless, and electric currents shot through the apparatus produce no effect. In the same manner the mere turning of the cylinder without electric action produces no effect, except to pull the diaphragm slightly out of shape. If while the cylinder is being turned an electric impulse arrives, the pull on the diaphragm, caused by the friction of the strip on the cylinder, is more or less released, and the diaphragm is free to vibrate or spring back into its original condition. If now, the electric impulses follow one another in regular order in correspondence with the sonorous vibrations imparted to the transmitting telephone, the alternate slipping and catching of the metal strip on the cylinder will follow in the same order, and thus the diaphragm will be made to vibrate in unison with the original vibrations, and thus reproduce the original words. As the mica disc is much larger than the disc of the transmitting instrument, the amplitude of its swing may be much greater, and consequently it will repeat the words with greater power. The electro-motograph is practically an apparatus for transforming electric action received from a distance into mechanical work. The amount of electric action has nothing to do with the amount of the mechanical work performed, because the movement of the cylinder is controlled by power independently of the electric action, the electricity merely releasing this power by destroying the friction in greater or less degree. The electric action set up by the sonorous vibrations at the transmitting end of the line may be very slight, while the mechanical action at the distant end may be powerful, and in this manner the amplitude of the vibrations may be increased to an indefinite extent, and a whisper may reappear as a loud shout.

“The electro-motograph is not only a solution of the telephone, making it capable of sounds of every quality and pitch and in greatly increased volume, but by this conversion of electrical action into mechanical work at a distance makes it possible to unite the telephone and phonograph. Telephonic messages by the electro-motograph may be impressed upon a self-acting (clock-work) phonograph, the same current starting and stopping the phonograph after the manner of the stock-reporting machines, and afterward the phonograph may be made to repeat the message impressed upon it.”

[The above extract, which explains the principle fully, has been taken from a long article on the subject which formerly appeared in Scribner’s Magazine.]

The uses to which the electro-motograph may be applied are various. It can produce mechanical motion even at a distance, and is useful to lessen friction by machinery; and in this way its service to railways and other locomotive systems may be estimated. It is a great help to telegraphy by increasing the speed of transmission, and can ascertain the beatings of the heart of the apparently dead. It amplifies sound in a much greater degree than the microphone, by which even a fly can be heard moving. In fact, the limit of the usefulness of this wonderful machine has not been reached.

Another very ingenious apparatus has been developed by Professor Bell. This is for the purpose of ascertaining the position of bullets in the body. The following is condensed from the Times:—

“Two conductors are used, and the ball completes the circuit. Professor Bell inserts a fine needle in the suspected region. It is connected by wire with one of the binding screws of a telephone, which the surgeon holds to his ear; the other binding screw being connected with a metallic mass applied to the skin. When the needle point touches the ball, an electric couple is formed, and the current generates the sound in the telephone. The surgeon may then use his knife with confidence, guided by the needle. He may make several insertions of the needle if necessary without danger, and any pain may be obviated by etherization. This simple method (which should prove useful on the field of battle) was tried with success with a lead ball introduced into a piece of beef. Contact of the needle with bone had no effect, but a very distinct sound was heard each time the ball was reached. A modification consists in inserting a vibrator in the circuit; this gives a musical note in the telephone at each contact of ball and needle. Again, if the circuit include a battery, the telephone sounds may be heard by several persons at once. A sound is heard, in this case, whenever the needle enters the skin; but, on reaching the ball, it is much intensified, owing to lessened resistance. A galvanometer may be used in place of the telephone.”

Mr. C. Vernon Boys has exhibited and described a very ingenious new integrating machine of his invention, and its application as a measurer of the electric energy in the circuit of an electric lamp or a dynamo-electric motor. Mr. Boys’ mechanical integrator belongs to the class termed tangent machines, and consists essentially of a small disc or wheel running along the surface of a drum or cylinder. When the wheel runs straight along the drum parallel to its axis there is no rotation of the latter, but when the wheel is inclined to the axis the drum rotates, and the integral is represented by the amount of rotation. Continuous action is secured in giving the drum a reciprocating motion along its axis, so that when the wheel has travelled to one end of the cylinder it can travel back again. The new integrator is especially adapted for measuring forces which are either delicate or variable. It is applied by causing the varying force to be measured to vary in a corresponding manner the inclination of the wheel to the axis of the rotating cylinder. In this way it can be used to find the work done by a fluid pressure reciprocating engine, or the energy transmitted by a shaft or belt from one part of a factory to another. By making the wheel very small and light, the strength of an electric current may be continuously measured, if the disc is inclined by means of the needle of a galvanometer in circuit. Mr. Boys has constructed on the same principle an electric energy meter, which integrates the product of the strength of current and the difference of potential between two points with respect to time. In it the current is passed through a pair of concentric solenoids or coils of wire, and in the annular space between these is hung a third solenoid, the upper half of which is wound in the opposite direction to its lower half. By the use of what Mr. Boys calls “induction traps” of soft iron, the magnetic force is confined to a small portion of the suspended solenoid, and by this means the attracting force of the fixed solenoids upon it is independent of position. The middle solenoid is hung from the end of a balance beam, and its motion is retarded by a counterweight, which admits of regulating the meter to give standard measure as a clock gives standard time. The motion of the beam is caused to incline the integrating wheel, and the rotation of the cylinder gives the energy expended in foot-pounds by means of an indicator or diagram, as the case may be. The object in giving an equal number of turns in opposite directions to the suspended solenoid is to render the instrument insensible to external magnetic forces.

We have, in a former portion of this work, explained the construction of the telephone and phonograph with other inventions to make sounds audible at a distance, so we need not repeat the explanations here. A brief reference to them will, however, be found in this chapter, in which the electro-magnet and the methods of lighting by magneto-electric machines are treated of. We will proceed to give some particulars concerning the electric light before considering the means by which it is produced, as such an arrangement is more convenient.

The light is very easily produced by uniting and then separating the terminals of a strong battery. The passage of the electric current induces intense heat and a most brilliant light. But if this were continued the wires would melt, and therefore some non-fusible substance is placed at the ends of the wires, which will be at once a conductor and infusible. Now in gas-carbon (the deposited substance found in gas retorts) we have a substance suited to these conditions. The carbon is heated to an intense brightness, and particles of it are passed across the arc of flame almost in a state of fusion. Combustion does not actually take place, because it has been proved that the wires will give out light under water, and in the vacuum of an air-pump the light is even increased, so that had the oxygen of the air any part in the production of the light it would not remain unaffected under these conditions. The heat arising from this Voltaic arc is intense, and even platinum may be fused with the assistance of the gas carbon. The carbon points are of course liable to be worn away, and one side more than another. The positive pole is generally more concave than the other, for it sheds its particles in a greater degree, and is the more intensely heated. The electric light first appeared in public at the opera in Paris in 1836, to illustrate a sunrise, but it was not till 1843 that it was experimented upon in the open air. We need not trace it farther at present, for a full account of its origin, rise, and progress is published in a small shilling volume by Messrs. Ward, Lock, & Co. We will proceed to the methods of bringing out the light.

There are various lamps, many of which required a regulator in consequence of the wearing away of the carbon points, as already explained. We append two illustrations of the Maxim lamp, the invention of Hiram Maxim, of New York. In both cuts the letters refer to the same portions.

In the first illustration (fig. 267), A and B are the positive and negative carbon-holders respectively, and the carbon points are controlled by an armature, which is, in its turn, adjusted by the screw, D. When it happens that the magnetic force is reduced the spring acts and permits the points to approach again, and the light is rekindled; the carbons are then locked till required to move. The second illustration (fig. 268) shows a section of the lamp with the wheel arrangements for controlling the advance of the carbon points as they waste away.

In the “Brush” light, which is in use in London, and is fitted for large spaces, the carbon points are held by a regulator side by side, and they last eight hours without renewal. The power is generated by an electro-dynamic engine. We give illustrations of the lamps of Wallace and Houston (figs. 269, 270). The current is conveyed through b and the magnet, m. The armature, a, separates the electrodes, and the weakened current is restored by b, and the light continues. The pillar, p, is hollow, with a wire running through it. The positive electrode is supported by J, the negative by C; V is a button which comes in contact with the lever, T, when the carbon points are exhausted, and cuts the lamp out of the circuit by passing it direct through mercury cups.

The Jablochkoff candle and chandelier are also represented (figs. 271, 272). The candles consist of carbons connected at the top, but otherwise insulated, and fixed in a socket. They do not last very long without renewal. The exhibition at the Crystal Palace will be essentially an Electric Light Exhibition, and all the latest forms can be studied there. The great attraction will doubtless be, as at Paris, the varied and numerous inventions of Mr. Edison. The early career of that American “magician” is now tolerably well known; his tremendous energy and application are fully appreciated. With only a few months schooling all his life he has taken a foremost place in the scientific world. In ten years he has invented the phonograph, the electric pen, a system of fast telegraphy, the electro-motograph, the telephone, a tasimeter, and other useful applications of electricity, besides solving the problem of electric light for domestic purposes.

Mr. Edison’s electric light[18] requires something more than a passing notice, and we will therefore endeavour to give a sketch of the general subject. Now that the electric light has been made available for domestic purposes, and the very simple lamp (consisting of an exhausted glass globe, two platinum wires, and a piece of charred paper) can be obtained, people will no doubt soon largely adopt electric lighting in their houses. The light has found a success at the theatre, in the streets, and in the train; there is no reason why it should not be adopted generally, being more economical and more healthy than gas.

If we sever an electric wire, and bring the ends, tipped with carbon, into juxtaposition, we obtain a brilliant light. This is the Voltaic arc we have already mentioned, produced by the incandescence of finely-divided matter; it was the first method of illuminating by electricity, and was discovered by Sir Humphrey Davy, who obtained a very brilliant light, but at great expense—about a guinea a minute! But the Daniell and Grove batteries and generators, and modern improvements in 1860, brought the use of the electric light into prominence. Faraday lighted a lighthouse with its assistance.

But when the GRAMME GENERATOR was invented the needed impetus was applied. The Jablochkoff candles followed, and now we have the electric light in full operation. So far we have sketched the history of illumination by the Voltaic arc, and descriptions of the various apparatus will be found at the end of this chapter. But the method of lighting with an incandescent solid was introduced in 1845 by Starr and Peabody, who took out a patent for the use of platinum. Later on Drs. Draper and Despretz made experiments with platinum and carbon. The latter gentleman sealed the carbon in an exhausted globe, and then introduced nitrogen in place of the air. But the method died out and was forgotten, and in 1873 a medal was actually given by the Academy of St. Petersburg for the “discovery” to Messrs. Sawyer and Mann.

In 1878 Paris was lighted with the electric candles of Jablochkoff. This application of electricity stirred up our transatlantic cousins, and Mr. Edison was requested—backed up by many influential persons—to make the investigation whether the light could be produced for domestic purposes. The celebrated electrician undertook the commission, and certainly came unprejudiced to the encounter, for he had not at that time even seen an electric light.

He perceived at once that “permanence in the lamp and the subdivision of the light” were the two desiderata. He put the Voltaic arc aside as unsuitable, and addressed himself to the problem of obtaining the desired results from an incandescent solid. The subdivision of the light is really an important point, and a comparison between divided and undivided burners is in favour of the more diffused light in a number of burners. This subdivision Edison worked hard to secure, and, as it is said of him, “With a steadfast faith in the fulness of nature, a profound conviction that if a new substance were demanded for the carrying out of some beneficial project, that substance need only be sought for, he set to work.”

Mr. Edison found difficulties in his way. One was the apparent impossibility of illuminating by means of an incandescent solid, for even platinum will melt at a heat too low for use. But this apparent impossibility was overcome by the inventor’s genius. He, after many trials, found that if he raised the platinum to a white heat in a vacuum he would practically obtain a new metal which would sustain the required heat.

“In making an electric lamp without a regulator,” says Mr. Upton, “two things are essential,—great resistance in the wire, and a small radiating surface. Mr. Edison sought to combine these two essential conditions by using a considerable quantity of insulated platinum wire wound like thread on a spool.” This platinum, as shown in the accompanying cut (fig. 273), was suspended in a glass bulb in vacuo, the air contained in it being expelled by electricity, heating it, and suddenly cooling the platinum, and squeezing out the air by the process. But, after all, the great difficulty of the inventor was to insulate his wires so perfectly that they would not meet and become a conductor. For, to perfect his lamp, this non-conducting principle was a necessity, otherwise the current would flow across instead of going all along the wires. He had previously made many uses of carbon, which we know is infusible. He tried lampblack tar, but it contained air, and would not do.

Thread answered his purpose, but was too fragile and uneven in texture. It suddenly occurred to him that paper—charred paper—cut into a thread-like form would satisfy all his conditions.

The problem was solved—the lamp was a fact. But how can paper, so easily burned, answer? We will endeavour to explain. “A piece of charred paper, cut into horse-shoe shape, so delicate that it looked like a fine wire firmly clamped to the two ends of the conducting and discharging wires, so as to form part of the electric circuit, proved to be the long-sought combination.”

We will now explain the construction of this little lamp, which is shown in the illustration (fig. 274) one-half of its actual size. The illuminating is equal to ten or twelve ordinary gas jets.

The manner in which the paper is prepared is, like many other very important inventions, extremely simple, and, we may add, almost costless. Cardboard will furnish us with the loops, and these “horseshoes” are placed in layers in an iron box with tissue paper between each. The box is then hermetically sealed, and made red hot. The carbonized paper remains till all the air has been got rid of, and although it will burn freely to ashes in atmospheric air, in the vacuum prepared for it it is never consumed. That is the plain fact—the secret of the Edison lamp.

A vacuum can now be produced almost perfect. It is of course impossible to extract every tiny particle of air from the globes, but by the Sprengel pump, in which mercury is employed, excellent vacuums are obtained. Several very curious phenomena have been observed in these vacuums, and the Royal Society has been engaged upon their consideration. Another advantage of the vacuum, as applied by Edison, is that little or no heat is generated. The electricity is all, or very nearly all, converted into light. Thus the glass globes remain almost unheated, and are unbroken.

The electric current passes along the wire, W, and at a certain place marked B, the copper is soldered to a platinum wire, which enters at C, and so by platinum clamps into the horse-shoe, L. The return wire is similarly arranged; the carbon is enclosed in a glass bulb, GG, and all the air is extracted by the pumps; the end is then sealed up by melting it at F.

The world is now in possession of a lamp for household use, and we are surprised that it is not more extensively adopted in England. There are some Swan lamps used in parts of the British Museum, and when we have explained the application of the light, and the uses to which the motive power can be applied, we shall, we believe, convince the most conservative gas bill advocate that Edison’s lamp is cheaper, safer, and far better in illuminating power than gas, if the success of the electric lamp can be assured.

We need not dwell upon the construction of the “pumping station,” for that is virtually what the magneto-electric generator is. Several of these stations can be established in various parts of the city, and each station will supply a district with electricity. The wires are laid in a tight box along the street, beneath the footpath, or other convenient position, and we are informed that the frost rather improves their electrical condition. Here is one advantage over gas.

From the main wires smaller ones enter the houses, and are carried through a “meter” containing a safety valve. There are two wires—a distributing wire and a waste—coloured, one red and the other green, which communicate respectively with the main supply and return wires to the “pumping station” or generator. The electricity is admitted between carbon points and flows round a magnet, the armature of which is held above it by a spring. If too much force be put on and any danger incurred, the magnet will attract the armature, and the current will cease. A snap connected by a small wire will then be closed by the electricity, and melting from the heat will cut off all the current. In ordinary circumstances the electricity passes through regulators (wire wound on spools) and on to a copper plate, “through a solution of copper salt.” Thus for every unit of current a certain quantity of copper is deposited. A certain standard amount represents five cubic feet, and the bills, based on the accumulation of copper, are made out like gas bills.

When the lamp is required a small handle is turned, and is instantly lighted; the reverse motion cuts off the current. “By touching a knob in the bedroom the whole house can be simultaneously lighted up” if desirable. No matches are necessary, as the lamps light themselves.

By adding a small electro-motor to the furniture of the house, and turning a handle, the sewing-machine can be worked by electricity, or lathes turned; and any business operations, such as lifting by cranes, etc., can be easily carried on.

The Swan electric lamps, which, with Mr. Edison’s, were exhibited in Paris, and will be found at Sydenham, give about twelve candle-power light. Edison’s lamps are made in two sizes, and vary accordingly. The Swan lamps give a very soft light, and are as easily manipulated as Edison’s. The Siemens system of lighting was also well seen in Paris, and the Faure storage system enables our trains to be lighted instantaneously by simply turning a handle. A full description of the Faure battery was given in the Times by Sir William Thomson, and in his address to the British Association at York in September last. He pointed out that in the accumulators of M. Faure,—which can be seen at 446, West Strand, London,—by means of a large battery it is quite easy to draw off electricity and to apply it as Edison proposed to do, in lighting our houses and do any little service. The electricity thus stored would be always ready for use, and would be supplied and paid for. It can be applied to any purpose, and locomotion by its means will ere long become more general. In Paris Dr. Siemens exhibited his electric tramway. This was an improvement upon the first Berlin tramway, for in it the horses frequently received shocks which they resented. In the later application the current comes from the generator by metal rods carried above the heads of the passengers alongside the line. Little rollers upon these are united with an electric machine in the tram-car. The current is sent along the wires, and reconverted into mechanical energy in the second machine, turns the wheels of the cars. In this way, as the car proceeds, the rollers overhead or alongside the track are kept moving by the car, and the connection is never broken.

But this is a digression. The electric light as applied to lighthouses was also exhibited, and any reader desirous to obtain full information upon the subject of lights and lighthouses will find it in a very pleasantly-written work by Mr. Thomas Stevenson, in which the various systems of lighting by electricity and otherwise are fully recounted, the conclusion being in favour of electricity, which is employed and has been used for years in France and in some English beacons. If its penetrative power can be finally established,—for some authorities maintain that the electric is more easily absorbed by fog than other light,—there is no doubt about its being universally adopted.

It is very interesting to watch the uses to which the electric light is being put. The latest experiment has been made by an Austrian, Doctor Mikerliez. Almost incredible as it may seem, the interior of the human stomach can now be illuminated by means of a wonderful little instrument called the Gastroscope, which is said to be actually in use and to have been favourably reported upon by the medical faculty of Vienna. There is at the end of a jointed flexible tube (which can be passed down the gullet) a miniature lamp, far more marvellous and mysterious than that of Aladdin, in which a strip of platinum is fixed and connected with fine wires conducting the electricity from a small battery. When contact is made, and the “light turned on,” the cavernous interior of the stomach is lit up. Still more extraordinary is the fact that the tube can be made to revolve, and the light reflected from the walls of the stomach and directed to the eye of the observer. There is necessarily a bend in the instrument, so that the light has literally to turn a corner before it reaches the surgeon’s eye; here the inventor’s skill and thorough knowledge of the laws of optics are brought into requisition. The reflected rays of light fall upon a sort of window situated a little above the lantern, and by means of prisms and a series of lenses, the light is twisted and turned about until it arrives at the eye-piece. No sensation of heat is to be feared, the little lamp being kept constantly cool by a reservoir of water.

Several contrivances have been invented within the last few years for examining the interior of the body, but they are very costly; the Gastroscope is likely to render great service to medical science.

The term “magneto-electric machine” is given to a collection of parts of mechanism intended to create or gather together induced electric currents. The invention of the magneto-electric machine was by no means a sudden inspiration, but the gradual result of a series of experiments and discoveries, the first of which, dating from 1820, may be said to be Œrsted’s observation, that a magnetised needle is deflected by the approach of an electric current as well as by that of a magnet, clearly proving that magnetism and electricity have some relation to one another. In the same year Arago discovered that a coil of insulated wire wound round a core of soft iron, converts it into a powerful magnet (i.e., an electro-magnet) when a current passes through the coil. It was in 1830, however, that our countryman Faraday proved the creation of a current by the action of a magnet on a coil of wire, and his experiment proved shortly as follows:—If a coil of wire be wound on a hollow core, and a permanent bar magnet be introduced into the hollow core, whilst introducing it a current may be proved (by a galvanometer), to be induced in the coil flowing in a certain direction, A B, which ceases as soon as the magnet is at rest in the centre of coil. On the withdrawal of the magnet a second current is induced flowing in the opposite direction, B A. Therefore it is clear that if a magnet be incessantly approached to and withdrawn from a coil of wire a constant succession of currents will be produced, and if a charged coil (i.e., a coil connected with the poles of a voltaic battery) take the place of the magnet a precisely similar result will be obtained. Now it will have been noticed that two opposite currents are constantly being formed, and as the object is to obtain a continuous flow of electricity in one given direction, or, in fact, divert or reverse the current instantly on its formation to make it practically the same current, for this purpose a commutator is used, and as for most purposes a commutator is one of the essentials of a magneto-electric machine, we will here give a description thereof. (See fig. 275.) The machine is composed of a cylinder, consisting of two metallic conducting halves, separated by a non-conducting layer. Whilst it is at rest the alternating currents, from being connected with the halves by the current, will pass to the two contact springs, and thence through the circuit. Now if (as is the case) the current is constantly changing, as has been noticed, the inverse current will at the first change pass through the same channels, but in another direction; but if at the instant of the reversal of the current the cylinder be revolved, the current flowing the reverse way will be guided through other channels respectively, instead of the original channels, and the direction of the current being changed at the same moment as the current itself, the two inversions neutralize themselves, and one constant current is produced. In a magneto-electric machine the commutator revolves identically with the magnet or armature, and the point at which sparks are being constantly produced is where the contact is being continually broken and made by the passage of the friction springs from over the non-conducting layer. The first machine formed on the basis of Faraday’s experiments was Pixii’s. It was composed of two uprights and a cross bar, to which is attached, hanging poles downwards, an electro-magnet; underneath this, the poles upwards, revolves a magnet. The commutator is fixed on the same axle and revolves with the permanent magnet. Saxton, and subsequently Clarke, made the obvious improvement of making the magnet less cumbrous and fixed, and causing the bobbins of the electro-magnet to revolve before or rather beside its poles; the commutator was fixed at the end of the axle on which the revolving bobbins (or armature) are fixed. Niaudat formed a compound Clarke machine, by setting two horse-shoe magnets a short distance apart. The armature revolves between them, and consists of twelve coils set between two plates; the coils are set alternately and connected,—i.e., the poles of the electro-magnets are set beside one another,—N. to S., S. to N., and so on, so that the N. pole receding produces a current; but the N. pole receding makes the S. pole approach, and produces another current, A B; in fact, a continuation of the same, for the approach of a N. pole naturally produces the same current as the recession of a S. pole; then as the S. pole in turn recedes it produces an inverse current, B A, which is in turn kept up by the approach of the next N. pole, and so on. Each coil is attached to a radiating metal bar, which conveys the current to be redirected to the commutator, which is affixed to the axle of the revolving armature as in Clarke’s machine. In 1854 Siemens completed his machine, the chief peculiarity of which was its cylindrical bobbin; the core is grooved deeply, parallel with its axis, and the wire is wound on cylindrically and covered with plates of brass; one end of the coil is fixed to the metal axis, the other to an insulated ferule at the end of the axis, where is also situate the commutator. This armature revolves between the poles by which it is closely embraced. One of the most celebrated of the magneto-electrical machines is that known as the “Alliance,” invented by Nollet, and perfected by Van Malderen. It is composed of four or six bronze discs, revolving on an axle, round the external circumference of each of which are set sixteen bobbins. This rotating compound armature revolves between four to six sets of horse-shoe magnets, which, being fixed radially to the centre, present in each set sixteen poles to the sixteen bobbins. It will be readily understood that this immense quantity of poles and bobbins produces a highly concentrated current, the ends of which proceed from the axle and an insulated ferule at its extremity.

In 1869 Mr. Holmes perfected his machine, which differs from all previous ones (except Pixii’s), in that the electro-magnets revolve in front of the coils instead of vice versâ; and besides magnetising his electro-magnets with part of the self-produced electricity, his bobbins are so disposed as to be able to keep several independent lights going at once. The Wylde machine consists, as it were, of two Siemens machines, one on the top of the other, the lower and larger of which is worked by an electro-magnet, which is magnetised by the action of the upper or smaller one, consisting in the ordinary way of a permanent magnet apparatus, which is termed “the exciting machine.” The longitudinal bobbin revolved between these permanent poles produces alternating currents, which are commutated (or redirected), and pass to work the larger and lower electro-magnet, which is composed of two large sheets of iron connected by a plate (on which stands the exciter). Its poles are two masses of iron separated by a layer of copper, and in this armature revolves the larger longitudinal bobbin. This lower machine is called the generator. Both bobbins are simultaneously revolved, and an intense current of electricity is thereby generated. Almost simultaneously with this one Mr. Ladd invented his machine, which is distinguished from all hitherto described by being composed of two parallel bar electro-magnets, between the extremities of which are placed two Siemens armatures, one smaller than the other; both being revolved, the smaller excites the electro-magnets, and the larger generates the electricity required. The wire is wound round the magnets so that the N. and S. poles face each other at each end. The chief advantage of the Ladd machine is the conversion of dynamic force into electricity, there always being just sufficient magnetism in an iron bar (by induction from terrestrial magnetism and other causes) to produce a very feeble current in the Siemens bobbin, and the bobbin taking it up and returning it to the electro-magnet, and the electro-magnet at once giving it back to the bobbin, the current gradually increases till the maximum is reached. And when we take into consideration this modicum of utilisable terrestrial magnetism, we may truly say in the words of M. Hippolyte Fontaine, “The mind is lost in contemplation of the succession of discoveries completing one another, and showing that with apparatus of small dimensions an infinite source of electricity could be produced if matter could withstand infinite velocities.” The Lontin machine, which supplied the current for the electric light which used to make night bright outside the Gaiety, is also composed of two parts, one dividing, the other generating the electricity produced. The principle of the dividing machine is somewhat similar to the alliance, excepting that a number of electro-magnets arranged radially round a core, revolve close to a corresponding number of bobbins fixed inside an iron cylinder, outside which is the collecting and dividing apparatus. The Maxim machine is constructed on the principle of sets of coils rotating between powerful electro-magnets. The Wallace machine was invented by the inventor of the Wallace-Farmer lamp. It consists of two horse-shoe electro-magnets placed side by side, the opposing poles facing each other. Each magnet has a rotating armature of twenty-five bobbins, on which the wire is wound quadruply, and the current generated by these coils is conducted away, passing through and exciting the electro-magnets, thus utilizing the residual and terrestrial magnetism before mentioned in connection with the Ladd machine; otherwise it partakes of the nature of the Niaudet machine.

We now come to what is perhaps the most perfect magneto-electric machine, which was first constructed by M. Gramme, a Parisian, in 1872, and differs in principle and construction from all those hitherto noticed. Its essential characteristic is a soft iron ring, round which is coiled one single continuous wire (i.e., the two ends are joined). Round the exterior surface of the wire coil a band is bared, and on this bared part two friction springs act. If the ring and coil be placed before the poles of a magnet, the ring will have two poles, S. and N., induced opposite the opposing poles N. and S. of the magnet; and if the ring revolve the poles will remain stationary, and as the coil revolves each coil of the wire will pass this induced pole, and as naturally half the coil will be inducted with one current, the other half (acted on by the other pole) will be charged with another or opposite current, which two kinds of electricity are carried away by the friction springs before mentioned. In the machine, as actually constructed, the soft iron ring is composed like the magnet or wire bundle of an induction coil, and the coils are set upon it side by side. Inside the ring are radially set insulated pieces, to each of which is attached the issuing end of one and the entering end of another bobbin; these answer the same purpose as the denudation of the external layer of wire. These pieces are bent so as to come out of the centre of the ring at right angles, and lay side by side (insulated) round a small cylinder. These, as they revolve, are touched by friction springs, which draw off the electricity induced in the coils in one continuous current. No sparks are produced at the contact of the friction springs, and there is no tendency to become heated. To obviate the inconvenience of the secondary or inverted current produced by the stopping of the machine, the inventor has contrived a circuit breaker on the principle of the electro-magnet, the magnets holding the circuit breaker in contact so long as the machine is working; but the decrease of velocity lessening the attractive power of the magnet, the circuit breaker opens by its own weight (or a counter-weight), and all danger of a reverse current is obviated. Experimental machines are manufactured by Bréquet & Cie (Paris), composed of Jamin’s magnets, and turned with a handle, and produce a force of eight Bunsen cells.

A great revolution, or rather the beginning of a new era in the history of electricity, may be said to have commenced with the perfection of M. Faure’s accumulators. These are troughs containing eleven lead plates, each coated with oxide of lead and wrapped in felt, the fluid being dilute sulphuric acid. The application of them to the electric light is one of their most valuable features; at the depôt in the Strand, where they may be seen at work, there are thirty such elements, each weighing about 50 lbs. It takes a two-horse-power engine working an Edison or Gramme machine six to eight hours to charge them, and when charged they will keep almost any number of lamps of sixteen-candle-power going some eight hours. They are used on the Brighton and South Coast Railway, and seem peculiarly adapted to lighting by incandescence, by Swan, or Edison’s lamp. The elements fully charged may be carried any distance without losing their electric power. And the stored force may be used for charging the accumulators themselves afresh from the machine. These accumulators may be seen any day at 446, Strand, and are well worth a visit.

The Gyroscope, though now an instrument common and familiar to all students, is none the less the subject of a problem, the solution of which is still to seek. It has indeed been entitled the paradox of mechanics; for though it depends on gravitation, gravitation yet appears indifferent to it. In order to render the operation of the Gyroscope as continuous as possible, so as to facilitate the profound study of its working, and also to unite another influence with those of the ordinary Gyroscope, producing phenomena of which this instrument affords us the spectacle, a learned American has employed electricity as a motive power.

The Gyroscope, shown in fig. 277, has a large, heavy pedestal, with a pointed column, which supports the instrument itself. The frame, of which the electro-magnets form a part, is connected with a rod, having at one end a hollow cavity which rests on the point of the vertical column. One of the extremities of the magnetic spool is attached to this cavity, the other end communicating with the bar which unites the two magnets. Over this bar is a spring which breaks the current, supported by an insulator in hard india-rubber; it is adjusted so that it touches a small cylinder on the axis of the wheel twice during every rotation of the latter. The wheel’s plane of rotation is at right angles with the magnets, and it carries an armature of soft iron, which rotates close to the magnet without touching it. The armature is so placed in relation to the surface of contact with the cylinder that breaks the current, that twice during each rotation, as the armature approaches the magnets, it is attracted; but immediately afterwards, as the armature comes directly in front of the magnets, the current is broken, and the acquired impulsion is sufficient to move the wheel until the armature comes again under the influence of the magnet. The spring which interrupts the current is connected with a thin copper wire, which stretches back as far as the point of the column, entwining it several times to render it flexible, finally bending down and plunging into some mercury enclosed in a round vulcanite cup placed on the column near the pedestal. The pedestal also bears two small stakes for receiving the wires of the battery, one connected with the column, and the other communicating by a small wire with the mercury contained in the vulcanite vessel. The magnets, the wheel, and all the connected parts can move in any direction round the point of the column. When two large Bunsen cells, or four small ones, are connected with the Gyroscope, the wheel turns with great rapidity, and allowing the magnets to operate, it not only sustains itself, but also the magnets and the other objects which are between it and the point of the column in opposition to the laws of gravitation. The wheel, besides turning rapidly round its axis, also effects a slow rotation round the column in the direction of the movement experienced by the lower part of the wheel. By placing the arm and the counterpoise of the machine as shown in fig. 277, so that the wheel and the magnets balance exactly on the pointed column, the whole machine rests stationary; but if we give the preponderance to the wheel and the magnets, the apparatus begins to rotate in a direction contrary to or following that of the upper part of the wheel.

The Gyroscope exemplifies very clearly the persistence with which a body undergoing a movement of rotation maintains itself in the plane of its rotation in spite of gravitation. It shows also the result of the combined action of two forces tending to produce rotations round two axes which are separate, but situated in the same plane. The rotation of the wheel round its axis, produced, in the present instance, by the electro-magnet, and the tendency of the wheel to fall or turn in a vertical plane, parallel to its axis, produce, as a result, the rotation of the entire instrument round a new axis which coincides with the column.

PEIFFER’S ELECTROPHORUS.

It will now perhaps interest our readers to describe a charming little plaything which is a great favourite with children, and which has the incontestable merit of early initiating them into all the principal phenomena of the statics of electricity, and teaching them the science of physics in an amusing form.

It is a small electrophorus invented by M. J. Peiffer, and reduced to such a point of simplicity, that it consists merely of a thin plate of ebonite, about the size of a large sheet of letter paper. The tinned wooden disc of the electrophorus which is found described in most treatises on physics, is replaced by a small sheet of tin, about the size of a playing-card, fastened on to the surface of the ebonite. The ebonite electrophorus produces electricity with remarkable facility. It must be placed flat on a wooden table, and thoroughly rubbed with the hand; if it is then lifted, and the sheet of tin lightly touched, a spark is elicited from ¼ inch to ½ inch in length. The electrophorus is completed by the addition of a number of small accessories in the shape of small dolls made of elder-wood, which exhibit in a very amusing manner the phenomena of attraction and repulsion. After the board has been charged with electricity, place the three little figures on the sheet of tin, and lift up the apparatus, so as to isolate it from any support. You will then see one little doll extending its arms, another with its silky hair standing on end, and a third, lighter than the others, leaping like a clown, and displacing as he does so the two small balls of elder-wood which have been placed on each side of him. We have given an illustration of the three figures performing at once (fig. 278), but they are generally used separately. M. Peiffer has indeed collected every known accessory for an electric machine, such as Geissler’s tube, the electric carillon, etc. These different experiments are all reduced to their simplest form, and, with their appliances, are all contained in a cardboard box. They are placed beside the electrophorus, which thus takes the place of an unwieldy electric machine. M. J. Peiffer accompanies this little portable cabinet with an exhaustive pamphlet, which is a valuable guide to the young physicist in studying the first principles of electricity.

“It is easy to discover in the education of children,” says M. Peiffer in his preface, “how to turn their budding faculties to the best account. Would you utilize them in a satisfactory manner?—Then put in their hands playthings which, in an attractive form, serve to familiarize them at an early age with those sciences, a knowledge of which will be at a later period absolutely indispensable to them; and they will be much more amused than with ordinary commonplace toys.”

These are sensible words, in which we heartily concur. Yes! Science properly taught, and properly understood, can indeed be brought within the range of children; it should give a lasting interest to all amusements, and form a part of the culture of the youthful mind, as at a later period it will contribute to the perfect development of the grown man.

MAGIC FISH.

An ingenious physicist, M. de. Combettes, who is a civil engineer at Paris, has devoted himself to constructing a number of playthings and scientific appliances for young people, among which we will describe the very curious one represented in fig. 279. A jar is filled with water, holding in suspension some fish made of tin, similar to those which children put in water and attract with a magnet. In this case, however, the mechanism is hidden, and the operator can turn the fish first in one direction and then in the other at pleasure. The secret of this experiment is easily explained by examining the illustration (fig. 279). In the wooden stand which supports the jar there is concealed a small electro-magnet which acts on the soft iron contained in the floating fish. When the current passes the small magnet turns round and attracts the little fish swimming in the water. This gyratory movement can be changed at pleasure by means of a regulator.

We will give an illustration of a few electric toys which M. Trouvé has found for us. In the picture (fig. 281) we see three different objects,—a rabbit beating a small bell, a representation of a bird with outstretched wings, and a pin surmounted by a skull. All these are capable of having movement imparted to them by means of electricity, although made and intended for ordinary use in the form of scarf-pin or other ornament.

Let us take the “death’s head” pin first. It is in gold, and enamelled with diamond eyes and articulated jaws. The rabbit is also gold, and carries two small drumsticks, with which he can play a tiny bell. This device also can be worn as a scarf-pin.

A conducting wire leads from the pin into the waistcoat pocket, where a small “pile,” about the size of a cigarette, is hidden away. If any one particularly admires the scarf-pin, all you have to do is to insinuate your fingers into your pocket, and you will, by contact, cause the electric current to act upon the pin in your scarf. The death’s head will at once begin to roll its eyes and grind its teeth, while the rabbit, under similar circumstances, will begin to play its bell with the greatest energy.

The handsome diamond bird represented in the centre of the illustration belongs to Madame de Metternich. When any lady wears it in her hair, she can, by the concealed wire, make it flap its jewelled wings, and by so doing cause much surprise amongst the spectators.

We will now endeavour to give a description of the manner in which these toys play their parts in company with the “hermetic-pile” which M. Trouvé has applied to many specialities that he has supplied to doctors, who use them largely.

This pile is formed by a “couple” of carbon and zinc hermetically enclosed in an ebonite box. The carbon and zinc only occupy one-half of the case. The liquid occupies the other. The sketch (fig. 280) on preceding page will explain the apparatus.

So long as the case is in its normal position the elements are not immersed in the solution, and consequently no electricity is developed. But as soon as the figure is placed in a horizontal or leaning position the force is generated; on readjusting the box the electric current is cut off, and all development ceases. Many curious electrical toys can be seen in Paris. Dolls are made to talk, and many other wonders for children can be easily procured.

ANIMAL AND ATMOSPHERIC ELECTRICITY.

Before concluding the subject of electricity we must devote a few pages to the consideration of the electric influence possessed by certain fishes, and to some of the phenomena of the atmosphere, especially thunderstorms. We have seen how Galvani experimented upon the limbs of frogs, and maintained that they possessed electricity; he attributed the current in the muscles to that cause. This theory Volta denied, but subsequently Nobili, in 1827, proved the existence of a current in the frog by means of a Galvanometer. This was conclusive, and the experiment was performed in the following manner:—He filled two vessels with salt and water, and into one he dipped the crucal muscles of a frog, and in the other the lumbar nerves were immersed. By putting these vessels in communication with his improved Galvanometer, which was extremely sensitive, he perceived a current passing from the feet towards the head of the animal.

It is, however, to Matteucci and Du Bois Reymond that the investigation of the phenomena of the courant propre are due. The former formed a “pile” of the thighs of frogs, and by placing the interior and exterior muscles in contact he formed a current from the inside to the outside muscles. This current is supposed to be occasioned by certain chemical changes which are continually taking place, and it continues longer in the case of a cold-blooded animal than in a warm-blooded one. There are many interesting papers on this subject included amongst the “Philosophical Transactions”; and the “Physical Phenomena of Living Beings” is fully treated in Matteucci’s lectures on that subject. In the “Transactions” for 1848 and subsequent years, other experiments may be perused, but space will not permit us to dilate upon them. The fact has been established, and we are told that muscles and nerves, as well as certain glands of the body, possess certain electrical properties.

The electricity of fishes, and the power possessed by the torpedo—whose name is now chiefly known in connection with warlike appliances—and the gymnotus, have been known for a very long time. This fish, popularly known as the electric eel, inhabits the warm fresh-water lakes of Africa, Asia, and America. A specimen was exhibited at the Polytechnic some years ago. This was the fish experimented on at the Adelaide Gallery by Professor Faraday, who clearly demonstrated the fact that the electricity of the animal and the common electricity are identical. Numerous experiments were made, and the circuit shock and even sparks were obtained from the gymnotus. In fact, the gymnotus is a natural electric machine. The force of the shock given by the electric eel is very great, for Faraday has put on record that a single discharge of the eel is equal to fifteen Leyden jars charged as highly as possible. Its power does not even end there, for having shocked people to that extent, it was capable of a second and occasionally of a third shock of less violence.

The manner in which the gymnotus acts is from a regular battery in the head, the sides of which are filled with a fluid. These cells are something like a honeycomb in appearance. The shock is quite voluntary on the part of the fish. Sometimes it will kill its prey, on other occasions it is merely numbed. Professor Faraday on one occasion placed a live fish in the tub with the gymnotus, which curled itself so as to enclose the unsuspecting one. In a second the prey was struck dead, and floated on the water. The gymnotus immediately devoured it, and went in quest of more. Another, but an injured fish, was then introduced, but the electric eel took no trouble about this one. It did not trouble to give it a shock, seeing it was disabled, it merely swallowed without killing it. It is also on record that on one occasion an electric eel had stunned a fish which, before he began to eat it, gave signs of returning animation; the eel immediately gave it another shock and killed it.

There were some other curious peculiarities connected with the electric eel. It appears to be quite capable of discriminating between animate and inanimate touch. For instance, when touched with a glass rod it at first gave signs of electricity, and discharged a shock at the attacking party. But on subsequent occasions, when touched with metal rods or glass, the fish declined to “shock”; nevertheless the Professor succeeded the moment he touched the animal with his hands.

The torpedo is something like the well-known skate; it is sometimes called the electric ray, and is common enough in the Bay of Biscay and in the Mediterranean Sea. It sometimes pays England a visit, or is caught by fishermen and brought in. We have seen one at Plymouth, and a very ugly-looking fish it was. Its electric power is considerable.

There is yet another fish known as the malapterurus; one species is called the thunder-fish. Professor Wilson has written a paper upon the electric fishes as applied to the remedy of disease, and considers them the “earliest electric machines ever known.”

Humboldt relates that the South-American Indians capture the gymnotus by driving horses into ponds which the electric eels are known to inhabit. The result is that the fish deliver shock after shock upon the unfortunate quadrupeds. Mules and horses have frequently been killed by these powerful eels, and even Faraday experienced a very great shock when he touched the head and tail of the captive gymnotus with either hand.

The malapterurus to which we have referred is an inhabitant of the African rivers, chiefly in the Nile and Senegal. Such a fish has been known with others for some hundreds of years; its electrical powers are not great. There are one or two other species of fish which possess electrical qualities, but none apparently to the same extent as the torpedo and the gymnotus.

The electricity of plants also is in some cases very marked. Flashes have been seen to come from some flowers in hot and dry weather. Currents of electricity have been detected, and Wartmann investigated the subject closely. He says the currents in flowers are feeble, but in succulent fruits and some kinds of grain they are very marked. These currents depend upon the season, and are greatest in the spring, when the plant is bathed in sap. These experiences were confirmed by Bequerel in 1850, and he concludes that the rank vegetation in some parts of the world must exercise considerable influence on the electric phenomena of the atmosphere. M. Buff has more recently made experiments in this direction, and he examined plants and trees, and even mushrooms. M. de la Rive, after carefully summing up the various theories, comes to the conclusion that it is to chemical reactions that the traces of electricity are due.

The subject of atmospherical electricity properly belongs to meteorology, and under that heading we will treat of it more fully. But lightning is so identified with electricity, and being the most common form observable to all, we will say something about thunderstorms and the electric discharges accompanying them.

Before Franklin’s ever-memorable experiment with his kite established the identity of lightning and electricity, the resemblance between the two discharges had been frequently noticed. The Etruscans pretended to bring down lightning from heaven, and Tullus Hostilius, when experimenting or performing certain “ceremonies,” was killed by the electric discharge he desired to attract. But after all, we cannot attribute any knowledge of electric science to the ancients, although they were, of course, familiar with electric phenomena.

It is to Dr. Wall that testimony points as the first person who remarked the analogy between the electric spark and lightning. This was in 1708. Grey and other philosophers supported the theory, but could not establish it. To Franklin, who in June 1752 actually brought down the lightning by his kite and a key, is the actual discovery due. We have already detailed the circumstances (page 206) and need not repeat the account of the experiment.

Of course the American philosopher found numerous imitators, not always with impunity. Professor Richmann was killed by the spirit he was invoking; Lemounier and Beccaria confirmed the theory that the air was full of electricity; while Du Saussure, from his investigations on the Alps, and Volta from the invention of the pile, are most famous in the history of electricity. They applied themselves with much success to the investigation of the electric condition of the atmosphere, of which the disturbances called thunderstorms are the result.

The amount of electricity varies in the atmosphere at different times in the day and night. Towards midday and midnight the development is generally greatest, and this fact will account for the prevalence of storms during our hours of rest. Again, different kinds of clouds have different degrees of electricity, and of different kinds. Under certain conditions these clouds will give forth lightning, and a storm will begin. The more clouds the more globules, and therefore in summer, while there is more production of vapour from solutions of salts, etc., we are more likely to have the storms. We are most of us familiar with the mass of the “thunder cloud” rising in the distance, light at the upper part, very dark below, and throwing out tentacles like the octopus, coming up sometimes—frequently, indeed—“against the wind,” impelled by an upper current, or following the course of a river, which is not unusual. Below, there is perhaps an army of thin dark clouds. The nature and height of clouds have also a great deal to do with the phenomena displayed. In general, storm-clouds are positively electrified.

Clouds are good conductors of electricity, and yet they may be so insulated by the dry air surrounding them that they will accumulate it; and when thus charged, if they encounter other clouds charged with opposite electricity, the opposing masses will attract each other until a discharge takes place. This is what we term lightning, and under such conditions electricity, though very dazzling, is harmless. It is when the cloud comes near to the earth, and a discharge is released, that lightning is so dangerous to persons who remain in the fields. Sometimes the discharge comes from the earth to meet that from the cloud. Sheep are frequently killed by ground lightning, and once, at Malvern, we had an escape from an upward stroke. The back-stroke from a cloud is also dangerous. It may happen that the cloud has discharged itself upon the earth many miles away, but a return discharge takes place at the other end, and if that end be near the earth the consequences may be serious. As a rule, the return stroke is not so violent as the first discharge.

The colour of lightning varies very much. We have the white, the blue, the violet, and red. The colour depends upon the distance and intensity of the lightning, and the more there is of it the whiter the light. We can illustrate the varied hues of the electric “fluid” by passing a spark through the receiver of an air-pump. If the air be rarefied, or there be a vacuum, we shall perceive a blue or violet light. Therefore we may conclude that the blue and violet flashes have birth in high strata of the atmosphere.

We have all heard how dangerous it is to stand under a tree during a thunderstorm, or rather, we should say, when the storm is approaching us nearly. The tree is a conductor, and the lightning having no better one at hand will pass through the tree on its way to the earth, and if we are standing against the tree we shall be included in the course, and die from the shock to the nerves while the lightning is passing through us. The best position in a thunderstorm, if we are in the neighbourhood of trees, is to sit or lie down on the ground some little distance from the base of the nearest tree. If the tree be sixty feet high suppose, and we sit fifty feet or less from the trunk, we shall be pretty safe, because the lightning will reach the tree top before it can reach us. We are protected by it as by a conductor, bad though it be. Standing up in a boat during a storm is not wise. Lightning has an affinity for water, and besides, if no higher objects are near, our body will act as a conductor. Bed is the safest place, as blankets are non-conductors. Cellars are not the safest by any means. Lightning may, and it frequently does, strike the house and descend to the basement. If the air be very full of electricity, and a flash be near, a person running away may conduct the lightning to himself by creating a vacuum into which the flash may dart.

Arago classified lightning into three kinds: zig-zag, globular, and sheet. The first we call forked lightning, and frequently this kind branches out at the end, so that although there may be only one flash, it may strike out in two or three directions at the same time. This may be accounted for by the unequal power of the air strata to conduct the electricity. The forked flashes are of very great length, extending frequently for miles, and the bifurcations also are often miles apart. The duration of the flash is less than the thousandth part of a second; so instantaneous is it that no motion can be perceived even in a most rapidly-moving wheel, as proved by Professor Wheatstone. We sometimes fancy that the flash lasts longer, but the impression received by the eye quite accounts for the apparently prolonged sight of the lightning.

Sheet lightning, the faint flashes frequently seen upon the horizon, are quite harmless. Sheet lightning is that which is seen reflected behind clouds or from far-distant storms. It is sometimes very beautiful. Ball, or globular lightning, is dangerous, and globes of fire have been seen to descend, and striking the ground, bound onwards for some distance. The descent of these forms of electric discharge has given rise to the popular notion of “thunderbolts.” The “Mariner’s Lights,” or St. Elmo’s fire, is frequently observed in ships. It is usually regarded as a fortunate occurrence. It was noticed by Columbus. One voyager describes the phenomena as follows:—“The sky was suddenly covered with thick clouds.... There were more than thirty of St. Elmo’s fires on the ship. One of them occupied the vane of the mainmast. I sent a sailor to fetch it. When he was aloft he heard a noise like that which is made when moist gunpowder is burned. I ordered him to take off the vane. He had scarcely executed this order, when the fire quitted it and placed itself at the apex of the mainmast, whence it could not possibly be removed.”

There have been occasions when the manes and tails of horses, and even the ears of human beings, have shown a phosphorescent light which emitted a hissing noise. Alpine travellers have noticed similar phenomena; and Professor Forbes, when crossing the Theodule Pass into Italy, heard the hissing sound in his alpenstock. The tips of rocks and grass points were all hissing too. The party were in the midst of an electric cloud. When the Professor turned the point of his alpenstock upwards, a vivid flash was emitted, but no thunder followed. They descended as quickly as possible from such a dangerous neighbourhood.

It is observable that the properties of lightning and of the electric spark are identical—the faint crackle of the latter being magnified into the loud rolling of the thunder. The disturbance of the atmosphere is the cause of the loud reverberations, and echoes produced from clouds tend to intensify and prolong the peal. The sound rises and falls, and varies accordingly as the cloud is near or far. A smart sharp report or rattle denotes the nearness of the lightning, while the gradual swelling and subsidence, followed, mayhap, by an increasing volume of sound, which in its turn dies away, tells us that the danger is not imminent. The cause o£ this loud rolling, unless it proceeds from echoes from different clouds, has not been satisfactorily explained. Sound travels less quickly than light, and therefore we only hear the thunder some seconds after we have perceived the flash. It is therefore conceivable that we may hear the last reverberations and its echoes first, and the sound of the first disturbance with its echoes last of all. Thus there will be distinct sounds. Firstly, the actual noise we call thunder from the air strata nearest to us; secondly, the echoes of that disturbance from the clouds, of course fainter; then we hear the sound caused by the tearing asunder of the air particles farthest off, and again the echoes of that disturbance. This theory will, we think, account for the swelling peals of thunder, and the successive loud and fainter reverberations. At any rate, in the absence of any other theory, we submit it for consideration. The sound of thunder is seldom or never heard at a distance greater than fifteen miles.

Lightning conductors are such every-day objects that no description is necessary; but the reason the lightning runs along it harmlessly is because the galvanized iron rod is the best conductor in the immediate neighbourhood. Where there is not a good conductor lightning will accept the next best, and so on, any conductor being better than none. The point of the rod cannot contain any electricity, there being no room for it, and the “fluid,” as it is termed, runs down to the ground, to terminate, when possible, in water or charcoal. A great deal of electricity is no doubt carried away from the air by the numerous conductors without any spark passing. Until Sir W. Snow Harris brought forward his lightning conductors for ships, the loss was great at sea. But now we rarely hear of any vessel being disabled by lightning. We owe to Franklin the idea of the lightning conductor.

According to observations made by Mr. Crosse, the following statement shows the tendency of the atmosphere, in certain conditions, to thunderstorms. We may accept the deduction of M. Peltier that grey and slate-colour clouds are charged with negative, and white, rose-colour, and orange clouds with positive electricity. The order of arrangement in the following table places the most likely source of thunderstorms first, and the least likely source at the end, with regular rotation of intermediate probabilities intervening:—

1. Regular thunder clouds. 2. Driving fog with small rain. 3. Fall of snow, or hailstorm. 4. Smart shower on a hot day. 5. Smart shower on a cold day. 6. Hot weather after wet days. 7. Wet weather after dry days. 8. Clear frosty weather. 9. Clear warm weather. 10. Cloudy days. 11. “Mackerel” sky. 12. Sultry weather and hazy clouds. 13. Cold damp night. 14. Cold, dry north-east winds.

We have thus briefly touched upon some of the atmospherical phenomena directly attributable to electricity. In our articles upon Meteorology we will consider the aurora and many other interesting facts concerning the atmosphere, and the effects of sound, heat, and light upon the air.

FOOTNOTES:

[18] We are indebted for many facts respecting Mr. Edison’s light in this chapter to a paper by Mr. Upton.

Spotted a typo or a problem in this chapter? Tell us

XXIII. AERONAUTICS

PRESSURE OF AIR IN BODIES—EARLY ATTEMPTS TO FLY IN THE AIR—DISCOVERY OF HYDROGEN—THE MONTGOLFIER BALLOONS—FIRST EXPERIMENTS IN PARIS—NOTED ASCENTS.

In the first part of this volume we entered into the circumstances of air pressure, and in the Chemistry section we shall be told about the atmosphere and its constituents. We know that the air around us is composed principally of two gases, oxygen and nitrogen, with aqueous vapour and some carbonic acid. An enormous quantity of carbonic acid is produced every day, and were it not for the action of vegetation the amount produced would speedily set all animal life at rest. But our friends, the plants, decompose the carbonic acid by assimilating the carbon and setting free the oxygen which animals consume. Thus our atmosphere keeps its balance, so to speak. Nothing is lost in nature.

We have illustrated the pressure of the atmosphere by the Magdeburg hemispheres, and we know that the higher we ascend the pressure is lessened. The weight of the atmosphere is 15 lbs. to the square inch at sea level. This we have seen in the barometer. Now pressure is equal. Any body immersed in a liquid suffers pressure, and we remember Archimedes and the crown. It displaced a certain amount of water when immersed. A body in air displaces it just the same. Therefore when any body is heavier than the air, it will fall just as a stone will fall in water. If it be of equal weight, it will remain balanced in the air, if lighter it will rise, till it attains a height where the weight of the atmosphere and its own are equal; there it will remain till the conditions are altered. Now we will readily understand why balloons float in the air, and why clouds ascend and descend in the atmosphere.

In the following pages we propose to consider the question of ballooning, and the possibility of flying. We all have been anxious concerning the unfortunate balloonist who was lost in the Channel, so some details concerning the science generally, with the experiences of skilled aeronauts, will guide us in our selection of material. We will first give a history of the efforts made by the ancients to fly, and this ambition to soar above the earth has not yet died out.

From a very early period man appears to have been desirous to study the art of flying. The old myths of Dædalus and Icarus show us this, and it is not to be wondered at. When the graceful flight of birds is noticed, we feel envious almost that we cannot rise from the earth and sail away at our pleasure over land and sea. Any one who has watched the flight of the storks around and above Strasburg will feel desirous to emulate that long, swift-sailing flight without apparent motion of wing, and envy the accuracy with which the bird hits the point aimed at on the chimney, however small. It is small wonder that some heathens of old time looked upon birds as deities.

The earliest flying machine that we can trace is that invented by Archytas, of Tarentum, B.C. 400. The historian of the “Brazen Age” tells us how the geometrician, Archytas, made a wooden pigeon which was able to sustain itself in the air for a few minutes, but it came down to the ground after a short time, notwithstanding the mysterious “aura spirit” with which it was supposed to be endowed. The capability of flying has for centuries been regarded as supernatural. Putting angels aside, demons are depicted with wings like bats’ wings, while witches, etc., possessed the faculty of flying up chimneys upon broomsticks. We even read in childish lore of an old woman who “went up in a basket” (perhaps a balloon-car), and attained a most astonishing altitude-an elevation no less than “seventy times as high as the moon!”

But to descend to history. It is undoubtedly true that in the time of Nero, Simon Magus attempted to fly from one house to another by means of some mechanical contrivance, and failing, killed himself. Roger Bacon, the “admirable doctor,” to whom the invention of gunpowder is generally attributed, had distinct notions of flying by means of machines, and “hollow globes,” and “liquid fire.” But he did not succeed, nor did many successive attempts succeed any better in subsequent years. Bishop Wilkins treated of the art of flying, but most, if not all who discussed the subject appear to have been indebted to Roger Bacon for the idea.

When the nature and pressure of the atmosphere by Torricelli’s experiments became better known, Father Lana, a Jesuit priest, constructed a flying machine or balloon of curious shape. He proposed to fix four copper globes, very thin, and about twenty feet in diameter, and to these he fastened a boat or car, looking very much like a basin. His idea was to empty his great copper globes, and that their buoyancy would then bear the weight of the traveller. But he overlooked or was ignorant of the effect of the atmospheric pressure, which would have speedily crushed the thin copper globes when empty. Lana’s suggestion was made in 1670, the barometer had been discovered in 1643.

There were some fairly successful experiments made in flying in 1678 and in 1709. The former attempt was made by Besmir, a locksmith of Sable, who raised himself by means of wings up to the top of a house by leaps, and then succeeded in passing from one house to another lower down by supporting himself in the air for a time. He started from an elevated position, and came down by degrees. Dante, a mathematician, also tried to fly, but without great success. He broke his thigh on one occasion. Laurence de Gusman claimed an invention for flying in 1709, and petitioned for a “patent,” which was granted by the king’s letter. The machine appears to have borne some resemblance to a bird.

It was not till 1782, however, that the true art of aerial navigation was discovered. The knowledge of hydrogen gas possessed by Cavendish in 1766 no doubt led up to it, and in the year following its discovery Professor Black, lecturing in Edinburgh, stated that it was much lighter than the atmosphere, and that any vessel filled with the gas would rise in the air. We now come to the invention of the BALLOON (so called from its shape being similar to a vessel used in the laboratory) by the Brothers Montgolfier.

Stephen and James Montgolfier were paper-makers, and carried on their business at Annonay, near Lyons, but it was partly by accident that the great discovery was made. They had no knowledge of the buoyancy of hydrogen gas. They took their idea of the balloon (inflated) from noticing an ascending column of smoke. It occurred to Stephen that if a paper bag were filled with smoke it would ascend into the air. A large bag was made and some paper burnt beneath it in a room. When the smoke had filled the bag it was released, and immediately ascended to the ceiling. Here was the germ of the Montgolfier or heated air balloon. The experiment was repeated in the open air with even greater success, and a trial upon a larger scale was immediately determined upon. A story is related of Mongolfier when prosecuting his researches, that a widow whose husband had belonged to the printing firm with whom Montgolfier was then connected in business, saw the smoke issuing from the room in which the little balloon was being filled. She entered, and was astonished to see the difficulty experienced by the experimenter in filling the balloon. It swerved aside, and increased the trouble he had to keep it above the chafing dish. Montgolfier was greatly troubled, and seeing his disappointment, the widow said, “Why don’t you fasten the balloon to the chafing dish?” This had not occurred to the experimenter, and the idea was a valuable one. That was the secret of success.

The Montgolfier Brothers determined to exhibit their successful experiment, and accordingly on the 5th of June, 1783, a great concourse assembled to see the wonderful sight. A large canvas or linen balloon was made and suspended over a fire of chopped straw. The heated air quickly filled the balloon, which rose high in the air, and descended more than a mile away. This balloon contained 22,000 cubic feet of heated air, which is lighter than cold air, and of course rising carried the globe with it. As soon as the air began to cool the balloon ceased to rise, and as it got colder descended.

Here was the actual discovery of the science of Aerostatics. The intelligence of the success achieved soon spread from France to other countries. Paris, however, was in advance, and the Brothers Robert applied hydrogen gas to a balloon which was sent up from the Champ de Mars in August 1783. There was some trouble experienced in filling it, but when the balloon was at length released it realized all expectations by remaining in the air nearly an hour. When at length it fell it met with a worse fate than it deserved, for the ignorant and superstitious peasantry at once destroyed it. After this Montgolfier exhibited his experiment next time at Versailles in the presence of the Court. The first aerial travellers appeared on this occasion—viz., a sheep, a cock, and a duck, which were secured in the car. They all descended in safety, and this success encouraged M. Pilatre de Rozier to make an attempt in a “fire balloon.” He went up first in a captive balloon, and at length he and a friend, the Marquis d’Arlandes, ascended from the Bois de Boulogne. The trip was a decided success, and the possibility of navigating the air was fully demonstrated.

Soon after this,—viz., in December 1783,—an Italian Count, named Zambeccari, made an ascent in London, and came down safely at Petworth. MM. Charles and Robert ascended from Paris in December, and in February a balloon crossed the English Channel. We must pass over some time and come to the ascents of Lunardi, which caused great excitement in London. His balloon was a very large one, and was inflated, or rather partially so, at the Artillery ground. Some delay occurred, and fearing a riot, M. Lunardi proposed to go up alone with the partially-filled balloon. A Mr. Biggin who had intended to ascend was left behind. The Prince of Wales was present, with thousands of spectators. Lunardi cast off and ascended rapidly, causing great admiration from the whole metropolis. Judge and jury, sovereign and ministers, all turned out to gaze at the balloon; a guilty prisoner was acquitted hurriedly, so that no time was lost in discussion, and one lady died of excitement. Lunardi was regarded as a hero, and made many other ascents. He died in 1806.

In those earlier days one or two fatal accidents happened. Count Zambeccari and a companion were in a balloon which caught fire, and both occupants of the car leaped from it as they were descending. The Count was killed on the spot, and his companion was much injured. Pilatre de Rozier made an attempt to cross the channel to England in 1785; he had reached three thousand feet when the balloon caught fire, and the unfortunate traveller was precipitated to the ground. His associate only survived him a few minutes.

It is to the celebrated English aeronaut, Mr. Green, that the substitution of carburetted hydrogen or street gas for hydrogen is due, and since his ascent in 1821 no other means of inflation have been used. A great many quite successful and a few unsuccessful ascents have been made for pleasure or profit. Mr. Green, in the Nassau balloon, passed over to Nassau, a distance of five hundred miles, in eighteen hours. This exploit was the cause of the name being bestowed upon the balloon. The Giant of M. Nadar was exhibited in England, and it was an enormous one, being an hundred feet high, and nearly as wide in the widest part. But even this machine was outdone by the Godard “Montgolfier” balloon, which was one hundred and seventeen feet high, and carried a stove. We give illustrations of these celebrated balloons, and will now pass on to the more scientific portion of the subject and the ascents of Mr. Glaisher and other aeronauts for the purpose of making meteorological observations, and the use of balloons for purposes of observation in war.

It appears that the first ascent for scientific investigation was made in the year 1803. The aeronauts were Messrs. Robertson and Lhoest. They ascended from Hamburg and came down at Hanover, and made meantime several experiments with reference to the electrical condition of the atmosphere, its influence upon a magnetic needle, and some experiments with regard to acoustics and heat. The report was presented to the St. Petersburg Academy, and contains the result of their interesting observations. The travellers ascertained that at the elevation to which they attained,—viz., 25,500 feet,—the temperature was on that July day fifty degrees colder, falling to 19·6°, while on the earth the thermometer had shown 68°. They ascertained that glass and wax did not become electric when rubbed, that the Voltaic battery lost much of its power, that the oscillation of a “dipping needle” increased as they mounted into the air, while sound was certainly less easily transmitted at that elevation, and struck them as less powerful in tone. The heat experiment was not a success, owing to the breaking of the thermometer. They wished to find the temperature of boiling water at that elevation, but when the experiment was about to be made Robertson accidentally plunged the instrument into the fire instead of into the water. So the question was not settled.

The effect upon the aeronauts was a sensation of sleepiness, and two birds died. The muscular powers of the voyagers also appear to have been much affected, and similar sensations may be experienced by travellers on high mountains who find their breath very short and a disinclination to exertion oppress them.

MM. Biot and Gay-Lussac made a very interesting ascent in 1804. We will detail their experiences at some length, for the coolness displayed and the value of the observations made are remarkable in the history of scientific ballooning. They started, at 10 o’clock a.m. on the 23rd of August, and when the balloon had carried them up to an altitude of 8,600 feet they commenced their experiments. They had some animals in the car with them, a bee amongst the number, and the insect was let go first. It flew away swiftly, not at all inconvenienced apparently. The sun was very hot at 56° Fahr. Their pulses were beating very fast, but no inconvenience was felt.

When 11,000 feet had been reached a linnet was permitted to go at large, but after a little time the bird returned to the balloon. It remained perched for a few minutes, and then dashed downwards at a tremendous pace. A pigeon was then liberated. It also appeared very uncertain, and wheeled around in circles for a time. At last it gained confidence, and descended, and disappeared in the clouds beneath. They made other experiments, but descended without having obtained as accurate results as had been anticipated.

On the next occasion, however, every care was taken, and on the 15th of September the important ascent was made by Gay-Lussac alone. He fixed hanging ropes to the balloon with the view to check the rotating movements, and having provided himself with all necessary apparatus and two vacuum flasks to bring down some of the upper air, the young man started. The barometer marked 30·66", the thermometer 82° (Fahr.). At an elevation of 12,680 feet Lussac perceived that the variation of the compass was the same as on land. Two hundred feet higher up he ascertained that a key held in the magnetic direction repelled with the lower, and attracted with its upper extremity the north pole of a needle. This experiment was repeated with the same result at an elevation of 20,000 feet, which shows how the earth exercises its magnetic influence. The temperature of the air was found to decrease in proportion as the ascent up to 12,000 feet, where the reading was 47·3°. It then increased up to 14,000 feet by 6°, and then regularly diminished again as the balloon rose, till at the greatest elevation reached, 23,000 feet, there was a difference of 67° in the temperature on the earth, for at the maximum height attained the thermometer stood at 14·9°.

But the most important fact ascertained, and one which set many theories at rest, was the composition of the atmosphere in those high altitudes. We mentioned that Gay-Lussac took up two empty flasks from which the air had been taken. The vacuum was almost perfect. When the aeronaut had reached 21,460 feet he opened one flask, and it was quickly filled; he secured it carefully; and when at his highest point,—four miles and a half above the sea-level,—he opened the other flask. The barometer stood at 12.95 inches, and the cold was very great. The voyager felt benumbed, and experienced difficulty of breathing; his throat was parched and dry. So Lussac determined to return, he could go no higher. He dropped gently near Rouen, and soon reached Paris. As soon as possible the air in the flasks was submitted to very delicate tests, and to the satisfaction of the scientists engaged it was found to be in exactly the same proportions as that collected near the earth—two hundred and fifteen parts of oxygen to every thousand of atmospheric air.

Messrs. Banal and Bixio, in 1850, also made some observations, and found the temperature very variable. At 23,000 feet they found the thermometer at minus 38·2° Fahr., which was much below the cold experienced by Gay-Lussac. We may still conclude that the various currents of the atmosphere cause considerable variation, and that it is impossible to lay down anything respecting the degrees of heat and cold likely to be found at certain elevations. We quote Arago’s observations upon this ascent:—

“This discovery” (the ice particles found in the air) “explains how these minute crystals may become the nucleus of large hailstones, for they may condense round them the aqueous vapour contained in the portion of the atmosphere where they exist. They go far to prove the truth of Mariotte’s theory, according to which these crystals of ice suspended in the air are the cause of parahelia—or mock-suns and mock-moons. Moreover, the great extent of so cold a cloud explains very satisfactorily the sudden changes of temperature which occur in our climates.”

M. Flammarion gives in his “Voyages” some very interesting and amusing particulars, as well as many valuable scientific observations. During one ascent he remarked that the shadow of the balloon was white, and at another time dark. When white the surface upon which it fell looked more luminous than any other part of the country! The phenomenon was an anthelion. The absolute silence impressed the voyager very much. He adds, “The silence was so oppressive that we cannot help asking ourselves are we still alive! We appear to appertain no longer to the world below.” M. Flammarion’s observations on the colour of what we term the sky are worth quoting—not because they are novel, but because they put so very clearly before us the appearance we call the “blue vault.” He says,—speaking of the non-existence of the “celestial vault,”—“The air reflects the blue rays of the solar spectrum from every side. The white light of the sun contains every colour, and the air allows all tints to pass through it except the blue. This causes us to suppose the atmosphere is blue. But the air has no such colour, and the tint in question is merely owing to the reflection of light. Planetary space is absolutely black; the higher we rise the thinner the layer of atmosphere that separates us from it, and the darker the sky appears.”

Some beautiful effects may be witnessed at night from a balloon, and considering the few accidents there have been in proportion to the number of ascents, we do not wonder at balloon voyages being undertaken for mere pleasure. When science has to be advanced there can be no objection made, for then experience goes hand-in-hand with caution. It is only the ignorant who are rash; the student of Nature learns to respect her, and to attend to her admonitions and warnings in time. The details of the ascents of famous aeronauts give us a great deal of pleasant and profitable reading. The phenomena of the sky and clouds, and of the heavens, are all studied with great advantage from a balloon, or “aerostat,” as it is the fashion to call it. The grand phenomena of “Ulloa’s circles,” or anthelia, which represent the balloon in air, and surrounded by a kind of glory, or aureola, like those represented behind saintly heads, appear, as the name denotes, opposite to the sun.

The various experiments made to ascertain the intensity of sounds have resulted in the conclusion that they can be heard at great distances. For instance, the steam whistle is distinctly audible 10,000 feet up in the air, and human voices are heard at an altitude of 5,000 feet. A man’s voice alone will penetrate more than 3,000 feet into the air; and at that elevation the croaking of frogs is quite distinguishable. This shows that sound ascends with ease, but it meets with great resistance in its downward course, for the aeronaut cannot make himself audible to a listener on the earth at a greater distance than 300 or 400 feet, though the latter can be distinctly heard at an elevation of 1,600 feet. The diminution of temperature noted by M. Flammarion is stated to be 1° Fahr. for every 345 feet on a fine day. On a cloudy day the mean decrease was 1° for every 354 feet of altitude. The temperature of clouds is higher than the air surrounding them, and the decrease is more rapid near the surface, less rapid as the balloon ascends. We may add that at high elevations the cork from a water-bottle will pop out as if from a champagne flask.

We have hitherto referred more to M. Flammarion and other French aeronauts, but we must not be considered in any way oblivious of our countrymen, Messrs. Glaisher, Green, and Coxwell, nor of the American,—one of the most experienced of aerial voyagers,—Mr. Wise. The scientific observations made by the French voyagers confirmed generally Mr. Glaisher’s experiments. This noted air-traveller made twenty-eight ascents in the cause of science, and his experiences related in “Travels in the Air,” and in the “Reports” of the British Association, are both useful and entertaining. For “Sensational ballooning” one wishes to go no farther than his account of his experience with Mr. Coxwell, when (on the 5th of September, 1862) he attained the greatest elevation ever reached, viz., seven miles, or thirty-seven thousand feet.

We condense this exciting narrative for the benefit of those who have not seen it already.

The ascent was made from Wolverhampton. At 1.39 p.m., the balloon was four miles high, the temperature was 8°, and by the time the fifth mile had been reached the mercury was below zero, and up to this time observations had been made without discomfort, though Mr. Coxwell, having exerted himself as aeronaut, found some difficulty in breathing. About 2 o’clock, the balloon still ascending, Mr. Glaisher could not see the mercury in the thermometer, and Mr. Coxwell had just then ascended into the ring above the car to release the valve line which had become twisted. Mr. Glaisher was able to note the barometer, however, and found it marked 10 inches, and was rapidly decreasing. It fell to 9¾ inches, and this indicated an elevation of 29,000 feet! But the idea was to ascend as high as possible, so the upward direction was maintained. “Shortly afterwards,” writes Mr. Glaisher, “I laid my arm upon the table possessed of its full vigour, and on being desirous of using it I found it powerless,—it must have lost power momentarily. I tried to move the other arm, and found it powerless also. I then tried to shake myself, and succeeded in shaking my body. I seemed to have no limbs. I then looked at the barometer, and whilst doing so my head fell on my left shoulder.”

Mr. Glaisher subsequently quite lost consciousness, and “black darkness” came. While powerless he heard Mr. Coxwell speaking, and then the words, “Do try, now do.” Then sight slowly returned, and rousing himself, Mr. Glaisher said, “I have been insensible.” Mr. Coxwell replied, “You have, and I, too, very nearly.” Mr. Coxwell’s hands were black, and his companion had to pour brandy upon them. Mr. Coxwell’s situation was a perilous one. He had lost the use of his hands, which were frozen, and had to hang by his arms to the ring and drop into the car. He then perceived his friend was insensible, and found insensibility coming on himself. There was only one course to pursue—to pull the valve line and let the gas escape, so as to descend. But his hands were powerless! As a last resource he gripped the line with his teeth, and bending down his head, after many attempts succeeded in opening the valve and letting the gas escape. The descent was easily made, and accomplished in safety.

Some pigeons were taken up on this occasion, and were set free at different altitudes. The first, at three miles, “dropped as a piece of paper”; the second, at four miles, “flew vigorously round and round, apparently taking a dip each time”; a third, a little later, “fell like a stone.” On descending a fourth was thrown out at four miles, and after flying in a circle, “alighted on the top of the balloon.” Of the remaining pair one was dead when the ground was gained, and the other recovered.

The observations noted are too numerous to be included here. Some, we have seen, were confirmed by subsequent aeronauts, and as we have mentioned them in former pages we need not repeat them. The results differed very much under different conditions, and it is almost impossible to decide upon any law. The direction of the wind in the higher and lower regions sometimes differed, sometimes was the same, and so on. The “Reports” of the British Association (1862-1866) will furnish full particulars of all Mr. Glaisher’s experiments.

We have scarcely space left to mention the parachutes or umbrella-like balloons which have occasionally been used. Its invention is traced to very early times; but Garnerin was the first who descended in a parachute, in 1797, and continued to do so in safety on many subsequent occasions. The parachute was suspended to a balloon, and at a certain elevation the voyager let go and came down in safety. He ascended once from London, and let go when 8,000 feet up. The parachute did not expand as usual, and fell at a tremendous rate. At length it opened out, and the occupier of the car came down forcibly, it is true, but safely. The form of the parachute is not unlike an umbrella opened, with cords attaching the car to the extremities of the “ribs,” the top of the basket car being fastened to the “stick” of the umbrella.

Mr. Robert Cocking invented a novel kind of parachute, but when he attempted to descend by it from Mr. Green’s balloon it collapsed, and the unfortunate voyager was dashed to pieces. His remains were found near Lee, in Kent. Mr. Hampton did better on Garnerin’s principle, and made several descents in safety and without injury.

The problem of flying in the air has attracted the notice of the Aeronautical Society, established in 1873, but so far without leading to practical results, though many daring and ingenious suggestions have been put forth in the “Reports.”

It is not within our province to do more than refer to the uses of the balloon for scientific purposes, but we may mention the services it was employed upon during the French war, 1870-71. The investment of Paris by the German army necessitated aerial communication, for no other means were available. Balloon manufactories were established, and a great number were made, and carried millions of letters to the provinces. Carrier-pigeons were used to carry the return messages to the city, and photography was applied to bring the correspondence into the smallest legible compass. The many adventures of the aeronauts are within the recollection of all. A few of the balloons never reappeared; some were carried into Norway, and beyond the French frontier in other directions. The average capacity of these balloons was 70,000 cubic feet.

Of course it will be understood how balloons are enabled to navigate the air. The envelope being partly filled with coal-gas-heated air and hydrogen, is much lighter than the surrounding atmosphere, and rises to a height according as the density of the air strata diminishes. The density is less as we ascend, and the buoyant force also is lessened in proportion. So when the weight of the balloon and its occupants is the same as the power of buoyancy, it will come to a stand, and go no higher. It can also be understood that as the pressure of the outside becomes less, the expansive force of the gas within becomes greater. We know that gas is very compressible, and yet a little gas will fill a large space. Therefore, as the balloon rises, it retains its rounded form, and appears full even at great altitudes; but if the upper part were quite filled before it left the ground, the balloon would inevitably burst at a certain elevation when the external pressure of the air would be removed, unless an escape were provided. This escape is arranged for by a valve at the top of the balloon, and the lower part above the car is also left open very often, so that the gas can escape of itself. When a rapid descent is necessary, the top valve is opened by means of a rope, and the balloon sinks by its own weight. Mr. Glaisher advises for great ascensions a balloon of a capacity of 90,000 cubic feet, and only filled one-third of that capacity with gas. Six hundred pounds of ballast should be taken.

A very small quantity of ballast thrown away will make a great difference; a handful will raise the balloon many feet, and a chicken bone cast out occasions a rise of thirty yards. The ballast is carried in small bags, and consists of dry sand, which speedily dissipates in the air as it falls. By throwing out ballast the aeronaut can ascend to a great height—in fact, as high as he can go, the limit apparently for human existence being about seven miles, when cold and rarefied air will speedily put an end to existence.

It is a curious fact, that however rapidly the balloon may be travelling through the air, the occupants are not sensible of the motion. This, in part, arises from the impossibility of comparing it with other objects. We pass nothing stationary which would indicate the pace at which we travel. But the absence of oscillation is also remarkable; even a glass of water may be filled brim-full, and to such a level that the water is above the rim of the glass, and yet not a drop will fall. This experiment was made by M. Flammarion. When the aeronaut has ascended some distance the earth loses its flat appearance, and appears as concave as the firmament above. Guide ropes are usually attached to balloons, and as they rest upon the ground they relieve the balloon of the amount of weight the length trailing would cause. They thus act as a kind of substitute for ballast as the balloon is descending. Most of the danger of aerial travelling lies in the descent; and though in fine weather the aeronaut can calculate to a nicety where he will descend, on a windy day, he must cast a grapnel, which catches with an ugly jerk, and the balloon bounds and strains at her moorings.

Although many attempts have been made to guide balloons through the air, no successful apparatus has ever been completed for use. Paddles, sails, fans, and screws have all been tried, but have failed to achieve the desired end. Whether man will ever be able to fly we cannot of course say. In the present advancing state of science it may not be impossible ere long to supply human beings with an apparatus worked by electricity, perhaps, which will enable them to mount into the air and sustain themselves. But even the bird cannot always fly without previous momentum. A rook will run before it rises, and many other birds have to “get up steam,” as it were, before they can soar in the atmosphere. Eagles and such heavy birds find it very difficult to rise from the ground. We know that vultures when gorged cannot move at all, or certainly cannot fly away; and eagles take up their positions on high rocks, so that they may launch down on their prey, and avoid the difficulty of rising from the ground. They swoop down with tremendous momentum and carry off their booty, but often lose their lives from the initial difficulty of soaring immediately. We fear man’s weight will militate against his ever becoming a flying animal. When we obtain a knowledge of the atmospheric currents we shall no doubt be able to navigate our balloons; but until then—and the information is as yet very limited, and the currents themselves very variable—we must be content to rise and fall in the air, and travel at the will of the wind in the upper regions of the atmosphere.

Spotted a typo or a problem in this chapter? Tell us

XXIV. CHEMISTRY

INTRODUCTION.

WHAT CHEMISTRY IS—THE ELEMENTS—METALLIC AND NON-METALLIC—ATOMIC WEIGHT—ACIDS—ALKALIS—BASES—SALTS—CHEMICAL COMBINATION AND STUDY.

Chemistry is the science of phenomena which are attended by a change of the objects which produce them. We know that when a candle burns, or when wood is burned, or even a piece of metal becomes what we term “rusty,” that certain chemical changes take place. There is a change by what is termed chemical action. Rust on iron is not iron; it is oxide of iron. The oxygen of the air causes it. So we endeavour, by Chemistry, to find out the nature of various bodies, their changes, and the results.

In nature we have simple and compound bodies. The former are called ELEMENTS. We must not confuse these elements with the so-called elements—earth, air, fire, and water. These are really compound bodies. An element is a substance or a gas which is not composed of more than one constituent; it is itself—a compound of perfectly identical particles. Every “compound” body, therefore, must be made up of some of the elements, of which there are sixty-five. These bodies are divided into non-metallic and metallic elements, and all bodies are composed of them, or are these bodies themselves. The list is as follows. The non-metallic elements are “metalloids.” We have omitted fractions from the weights, on which chemists differ.

TABLE OF ELEMENTS WITH THEIR CHEMICAL SYMBOLS AND COMBINING WEIGHTS.

Non-Metallic Atomic or Elements. Symbols. Combining Derivation of Name. Weights.

Oxygen O 16 Gr. Oxus, acid; gennaō, to make. Hydrogen } { H 1 Gr. Udor, water; gennaō, to make. Nitrogen } Gaseous { N 14 Gr. Natron, nitre; gennaō, to make. Chlorine } {Cl 35 Gr. Chloros, green. Iodine } { I 127 Gr. Ioeides, violet. Fluorine } { F 19 Fluor spar, the mineral. Carbon } { C 12 Lat. Carbo, coal. Sulphur } { S 32 Lat. Sulphurium. Phosphorus } { P 31 Gr. Phos, light; pherein, to carry. Arsenic* } Solid{ As 75 Gr. Arsenicon, potent. Silicon } { Si 28 Gr. Silex, flint. Boron } { B 11 Gr. Borax, Arab., baraga, to shine. Selenium } { Se 79 Gr. Selene, the moon. Tellurium } { Te 129 Lat. Tellus, the earth. Bromine Fluid 80 Gr. Bromos, offensive smell.

METALS.

Name. Symbols. Atomic or Derivation. Combining Weights.

Aluminium Al 27 Lat. Alumen, alum. Antimony (Stibium) Sb 122 Gr. Anti, against; minos, one. [Arsenic] As 75 (Not known.) Barium Ba 137 Gr. Barsù, heavy. Bismuth Bi 210 Ger. Weissmuth, white matter. Cadmium Cd 112 Gr. Cadmeia, calamite. Cæsium Cs 133 Lat. Cæsius, sky-blue. Calcium Ca 40 Lat. Calx, lime. Cerium Ce 141 The planet Ceres. Chromium Cr 52 Gr. Chroma, colour. Cobalt Co 58 Ger. Kobald, a sprite. Copper Cu 63 Lat. Cuprum (Cyprium), Cyprus. Didymium D 147 Gr. Didumos, twins. Erbium E — Ytterby in Sweden. Gallium Ga 70 (Not known.) Glucinum Gl 9 Gr. Glukos, sweet. Gold Au 197 From Hebrew, to shine (doubtful). Indium In 113 Indigo colour. Iridium Ir 198 Gr. Iris, rainbow. Iron Fe 56 Hebrew, to meet (doubtful). Lanthanum La 139 Gr. Lanthanein, to lie hid. Lead Pb 207 (Plumbum) malubodos (galena). Lithium Li 7 Gr. Lithos, stone. Magnesium Mg 24 Magnesia, Asia Minor. Manganese Mn 55 Mangana, E. I. (or Magnesia). Mercury Hg 200 Heathen deity (quick). Molybdenum Mo 96 Gr. Molybdena, lead ore, like lead. Nickel Ni 58 Ger. Kupfer nikel, false copper. Niobium (Columbium) Nb 94 Columbite. Osmium Os 199 Osme, an odour. Palladium Pl 106 Pallas, Minerva. Platinum Pt 197 Spanish, platina, little silver. Potassium (Kalium) K 39 Potash. Rhodium Rh 104 Gr. Roda, rose. Rubidium Rb 85 Lat. Rubidus, red. Ruthenium Ru 104 (Not known.) Silver (Argentum) Ag 108 Hebrew, money. Sodium (Natrium) Na 23 Salsoda plant. Strontium Sr 87 Strontian, N.B. Tantalum Ta 182 Tantalite mineral. Terbium Tr — (Not known.) Thallium Tl 204 Gr. Thallos, green twig. Thorium Th 230 Thor, deity. Tin (Stannum) Sn 118 (Not known.) Titanium Ti 50 Titans. Tungsten (Wolfram) W 184 Swedish. Uranium U 240 Urania. Vanadium V 51 Vanadis, a goddess in Sweden, etc. Yttrium Y 93 (Not known.) Zinc Zn 65 Ger. Zinken, nails. Zirconium Zr 89 Ger. Zircon, four-cornered (Ceylon).

*Arsenic is sometimes considered a non-metallic and sometimes a metallic substance.

The term “combining weight” requires a little explanation. We are aware that water, for instance, is made up of oxygen and hydrogen in certain proportions. This we will prove by-and-by. The proportions are in eighteen grains or parts of water, sixteen parts (by weight) of oxygen, and two parts (by weight) of hydrogen. These are the weights or proportions in which oxygen and hydrogen combine to form water, and such weights are always the same in these proportions. Chemical combination always occurs for certain substances in certain proportions which never vary in those compounds, and if we wish to extract oxygen from an oxide we must take the aggregate amount of the combining weights of the oxide, and we shall find the proportion of oxygen; for the compound always weighs the same as the sum of the elements that compose it. To return to the illustration of water. The molecule of water is made up of one atom of oxygen and two atoms of hydrogen. One atom of the former weighs sixteen times the atom of the latter. The weights given in the foregoing table are atomic weights, and the law of their proportions is called the Atomic Theory.

An atom in chemistry is usually considered the smallest quantity of matter that exists, and is indivisible. A molecule is supposed to contain two or more atoms, and is the smallest portion of a compound body. The standard atom is hydrogen, which is put down as 1, because we find that when one part by weight of hydrogen is put in combination, it must have many more parts by weight of others to form a compound. Two grains of hydrogen, combining with sixteen of oxygen, makes eighteen of water, as we have already seen.

Take an example so plainly given by Professor Roscoe, remembering that the numbers in our table represent the fixed weight or proportion by weight in which the simple body combines. The red oxide of mercury contains sixteen parts by weight of oxygen to two hundred parts by weight of mercury (we see the same numbers in the table); these combined make two hundred and sixteen parts of oxide. So to obtain 16 lbs. of oxygen we must get 216 lbs. of the powder. It is the same all through, and it will be found by experiment that if any more parts than these fixed proportions be taken to form a compound, some of that element used in excess will remain free. Lime is made up of calcium and oxygen. We find calcium combining weight is forty, oxygen sixteen. Lime is oxide of calcium in these proportions (by weight).

When we wish to express the number of atoms in a compound we write the number underneath when more than one; thus water is H_{2}O. Sulphuric acid H_{2}SO_{4}. As we proceed we will give the various formulæ when considering the chief elements.

In chemistry we have acids, alkalis, and salts, with metallic oxides, termed bases, or bodies, that when combined with acids form salts. Alkalis are bases.

ACIDS are compounds which possess an acid taste, impart red colour to vegetable blues, but lose their qualities when combined with bases. Hydrogen is present in all acids. There are insoluble acids. Silicic acid, for instance, is not soluble in water, has no sour taste, and will not redden the test litmus paper. On the other hand, there are substances (not acids) which possess the characteristics of acids, and most acids have only one or two of these characteristics.

Thus it has come to pass that the term “acid” has in a measure dropped out from scientific nomenclature, and salt of hydrogen has been substituted by chemists. For popular exposition, however, the term is retained.

ALKALIS are bases distinguished by an alkaline taste. The derivation is from Arabic, al-kali. They are characterized by certain properties, and they change vegetable blues to green, and will restore the blue to a substance which has been reddened by acid. They are soluble in water, and the solutions are caustic in their effects. Potash, soda, and ammonia are alkalis, or chemically, the oxides of potassium, sodium, ammonium, lithium, and cæsium are all alkalis. Potash is sometimes called “caustic” potash. There are alkaline earths, such as oxides of barium, strontium, etc. Bases may be defined as the converse of acids.

Acids and alkalis are then evidently opposite in character, and yet they readily combine, and in chemistry we shall find that unlike bodies are very fond of combining (just as opposite electricities attract each other), and the body made by this combination differs in its properties from its constituents.

SALTS are composed of acids and bases, and are considered neutral compounds, but there are other bodies not salts, which likewise come under that definition—sugar, for instance. As a rule, when acids and alkalis combine salts are found.

Chemical phenomena are divided into two groups, called inorganic and organic, comprising the simple and compound aspects of the subject, the elementary substances being in the first, and the chemistry of animals or vegetables, or organic substances, in the latter. In the inorganic section we shall become acquainted with the elements and their combinations so often seen as minerals in nature. Chemical preparations are artificially prepared. To consider these elements we must have certain appliances, and indeed a laboratory is needed. Heat, as we have already seen, plays a great part in developing substances, and by means of heat we can do a great deal in the way of chemical decomposition. It expands, and thus diminishes cohesion; it counteracts the chemical attraction. Light and electricity also decompose chemical combinations. But before proceeding it will be as well to notice a few facts showing how Nature has balanced all things.

The earth, and its surrounding envelope, the atmosphere, consist of a number of elements, which in myriad combinations give us everything we possess,—the air we breathe, the water we drink, the fire that warms us, are all made up of certain elements or gases. Water, hydrogen and oxygen; air, oxygen and nitrogen. Fire is combustion evolving light and heat. Chemical union always evolves heat, and when such union proceeds very rapidly fire is the result.

In all these combinations we shall find when we study chemistry that not a particle or atom of matter is ever lost. It may change or combine or be “given off,” but the matter in some shape or way exists still. We may burn things, and rid ourselves, as we think, of them. We do rid ourselves of the compounds, the elements remain somewhere. We only alter the condition. During combustion, as in a candle or a fire, the simple bodies assume gaseous or other forms, such as carbon, but they do not escape far. True they pass beyond our ken, but nature is so nicely balanced that there is a place for everything, and everything is in its place under certain conditions which never alter. We cannot destroy and we cannot create. We may prepare a combination, and science has even succeeded in producing a form like the diamond—a crystal of carbon which looks like that most beautiful of all crystals, but we cannot make a diamond after all. We can only separate the chemical compounds. We can turn diamonds into charcoal it is true, but we cannot create “natural” products. We can take a particle of an element and hide it, or let it pass beyond our ken, and remain incapable of detection, but the particle is there all the time, and when we retrace our steps we shall find it as it was before.

This view of chemistry carries it as a science beyond the mere holiday amusement we frequently take it to be. It is a grand study, a study for a lifetime. Nature is always willing, like a kind, good mother as she is, to render us up her secrets if we inquire respectfully and lovingly. The more we inquire the more we shall find we have to learn. In these and the following pages we can only tell you a few things, but no one need be turned away because he does not find all he wants. We never do get all we want in life, and there are many first-rate men—scientists—who would give “half their kingdom” for a certain bit of knowledge concerning some natural phenomena. There are numerous excellent treatises on chemistry, and exhaustive as they are, at present they do not tell us all. Let these popular pages lead us to the study of nature, and we shall find our labour far from onerous and full of interest, daily increasing to the end, when we shall know no more of earth, or chemistry.

As a preliminary we will put our workshop aside, and show you something of Chemistry without a Laboratory.

Spotted a typo or a problem in this chapter? Tell us

XX. GALVANISM…

Cite this passage

MLA

APA

Chicago

XX. GALVANISM

XXI. MAGNETISM

Chapter XXII

XXIII. AERONAUTICS

XXIV. CHEMISTRY