ment. None of the ordinary practices judiciously enjomed by the Humane Society, should ever, on such occasions, be neglected. For it is surely criminal to spare any pains which may contribute, in the slightest degree, to recall the fleeting breath of man to its cherished mansion.'

266. We have hitherto confined ourselves to the effects of small batteries, but we must not omit to notice the powerful Voltaic apparatus constructed by Mr. Children, as well as the results obtained by it, or the more portable as well as powerful arrangement by Mr. Pepys. In the first of these arrangements, the copper and zinc plates of the apparatus were connected together, in the usual order, by leaden straps, six feet long by two feet eight inches broad, each plate presenting thirty-two square feet of surface. All the plates being attached to a strong wooden frame suspended by ropes and pulleys, which, being balanced by counterpoises, was easily lowered and elevated, so as to immerse the plates in the acid, or raise them out of it at pleasure. The cells of the battery were twenty-one in number, and their united capacities amounted to 945 gallons. To each pole of the battery a leaden pipe, about three-fourths of an inch in diameter, was attached by solder, and the opposite end of each pipe immersed in a basin of mercury (a separate basin for each pipe), by means of which the circuit was completed, and a perfect contact ensured. The battery was afterwards improved at the suggestion of Dr. Wollaston, and the copper coiled completely round each zinc surface. See fig. 3, plate II. The first experiments we shall mention were made on the comparative facility with which different metals are ignited when placed in the electrical circuit. For this purpose, in each experiment, two wires of dissimilar metals were taken, of equal diameter and length; one end of each was in contact with one of the basins of mercury communicating with the poles of the battery, and the other end bent to an angle, and the wires connected continuously by hooking them together. The length of each wire was eight inches, and the diameter one-thirtieth of an inch. The battery was moderately excited by a charge of one part acid diluted with forty parts of water.

267. Experiment I.-A platina and a gold wire being thus connected, and introduced into the electrical circuit, the platina was instantly ignited, the gold remained unaffected.

268. Experiment II-A similar arrangement of gold and silver wires. The gold was ignited,

the silver not.

269 Experiment III.-The same with gold and copper. No perceptible difference in the state of ignition; both metals were heated red.

270. Experiment IV.-Gold and iron. The iron was ignited; the gold unchanged.

271. Experiment V.-Platina and iron. The iron ignited instantly at the point of contact next the pole of the battery. Then the platina became ignited through its whole extent. After this the iron became more intensely heated than he platina, and the ignition of the latter decreased.

272. Experiment VI.-Platina and zinc. The platina was ignited: the zinc was not; but

melted at the point of contact. In a subsequent experiment, the zinc did not melt; but the platina ignited as before.

273. Experiment VII.-Zine and iron. The iron was ignited: the zine bore the heat without fusing.

274. Experiment VIII-Lead and platina. The lead fused at the point of contact.

275. Experiment IX.—Tin and platina. The tin fused at the point of contact. No ignition of either wire took place in the two last experiments.

276. Experiment X.-Zinc and silver. The zinc was ignited before it melted: the silver was not ignited.

277. The results in every case were the same to whichever pole of the battery either wire was presented. These experiments were varied by introducing several alternations of different wires continuously connected, into the circuit, and obtained in every instance analogous results. Thus,

278. Experiment XI.-Alternations of platina and silver, three times repeated: all the platina wires were ignited, and none of the silver.

279. Experiment XII.-One zinc wire between two platina: both the platina wires were ignited, the zinc not.

280. Experiment XIII.-One iron between two platina. Both the latter first ignited; then the iron, which soon became fully heated, and fused.

281. It is unnecessary to enter into a farther detail of these experiments; it will be sufficient to say generally, that when wires of several different metals were introduced at once into the circuit, the order of their ignition was precisely that of the former experiments. In one experiment the copper was decidedly most heated.

282. To explain these phenomena, Mr. Children supposes that when a perfect communication is established between the poles of the battery, the electricity circulates without producing any visible effect; but, if it meet with resistance in its passage, it manifests itself by chemical action, by the evolution of heat, or both. Thus, if a bar of metal be connected with one pole of the battery, and its extremity immersed in a basin of mercury connected with the other pole, at the instant the surfaces come in contact, heat and light are evolved, which cease as soon as the bar, if it be of sufficient size, is fairly plunged beneath the surface of the quicksilver. If the circuit be completed by two pieces of charcoal, the evolution of heat and light is permanent, as long as their surfaces remain in contact, because that contact can never be so perfect, as to oppose no resistance to the electricity; whereas, in the case of the bar of metal and the mercury, it soon becomes complete, and the current is then uninterrupted. Resistance, therefore, appears to occasion the development of heat (whatever be the ultimate cause of the phenomenon), and as this must be inversely as the conducting power, when any two of the wires connected continuously are placed in the circuit, that which is the worst conductor must be most heated; and thus platina, having the lowest conducting power, is ignited before all

the rest; and silver, which conducts best, is not heated red when connected with any of the other metals.

283. The following experiments were made with the battery in a high state of excitation; and Mr. Children considers them as representing nearly the maximum of effect which it is capable of producing. As the quantity of acid was increased from time to time, and that previously added often almost spent before fresh was put in, it is not easy to say exactly what proportion it bore to the water; perhaps the largest may be stated at about th. On this, as on former occasions, he found a mixture of nitrous and sulphuric acids, to produce the most powerful and permanent effects.

284. Experiment I.-Five feet six inches of platina wire, of an inch in diameter, were neated red throughout, visible in full daylight. 285. Experiment II.-Eight feet six inches of platina wire, of an inch in diameter, were heated red.

286. Experiment III.-A bar of platina of an inch square, and 2 inches long, was also heated red, and fused at the end; and,

287. Experiment IV.-A round bar of the same metal, of an inch in diameter, and 24 inches long, was heated bright red throughout.

288. Experiment V.-Fine points of boxwood charcoal intensely ignited in chlorine, neither suffered any change, nor produced any in the gas. The result was similar when heated in azote.

296. Experiment VII.-Compound ore of iridium and osmium; fused into a globule.

297. Experiment VIII.-Pure iridium; fused into an imperfect globule, not quite free from small cavities, and weighing 71 grains. The metal is white, very brilliant, and in its present state its specific gravity is 18.68, which must be much too low, on account of the porous state of the globule. In the Minutes of the Experiments, in July 1813, mention is made of the fusion of a small portion of pure iridium into a globule weighing of a grain, which had been previously submitted to the action of a battery of 2000 plates, of four inches square, without melting.

298. Experiment IX.-Ruby and sapphire, were not fused.

299. Experiment X.-Blue spinal ran into a slag.

300. Experiment XI.-Gadolinite, fused into globules.

301. Experiment XII.-Magnesia was agglutinated.

302. Experiment XIII.-Zircon from Norway was imperfectly fused.

303. Experiment XIV.-Quartz, silex, and plumbago, were not affected.

290. Experiment I.-Oxide of tungsten, which (as well as other metallic oxides operated on) had been previously intensely ignited in a charcoal crucible, in a powerful furnace, fused, and was partially reduced. The metal grayish white, heavy, brilliant, and very brittle.

291. Experiment II.-Oxide of tantalum. A very small portion fused. The grains have a reddish-yellow color, and extremely brittle.

292. Experiment III.--Oxide of uranium; fused, but not reduced.

293. Experiment IV-Oxide of titanium; fuse 1, not reduced. When intensely heated, it burnt, throwing off brilliant sparks like iron.

294. Experiment V.-Oxide of cerum; fused, and when intensely heated it burnt with a large, vivid white flame, and was partly volatilised, but not reduced. The fused oxide, on exposure for a few hours to the air, fell into a light brown powder, containing numerous shining particles of a silvery lustre interspersed amongst it, and exhaled an odor, similar to that of phosphureted hydrogen.

295. Experiment VI.-Oxide of molybdena; readily fused and relucel. The metal is very Drittle, of a steel gray color, anl soon becomes covered with a thin coat of purple oxide.

periment, using, instead of the carbonate, caustic lime, and obtained also what he considered to be cast steel; whence he concluded that the carbon necessary to convert the iron into steel had not been furnished, as Clout supposed, by decomposition of the carbonic acid, but that it had found its way from the ignited gas of the furnace to the iron. This result occasioned suspicions of the accuracy of the de uctions from the experiment with the diamond; and Mr. Mushet accordingly, at the suggestion of the editor of the Philosophical Magazine, repeated the experiment made at the Polytechnic School, only keeping out the diamond. The results (for he made several experiments), uniformly gave him good cast steel, whence he concludes that we are still without any satisfactory or conclusive proof of the steelification of iron solely by means of the diamond; and adds that he doubts whether the diamond afforded even one particle of carbon to the iron. The details of both Clouet's and Mushet's experiments, may be found in the fifth volume of the Philosophical Magazine. Sir George M'Kenzie repeated both results confirming the conclusions of the French chemist. The labors of this gentleman would at first view appear conclusive; but, if a doubt should remain, it occurred to Mr. Pepys, that the battery would afford an experimentum crusis on the subject; and his ingebuity readily suggested a mode of making it, every way unobjectionable. He bent a wire of pure soft iron, so as to form an angle in the middle, in which part he divided it longitudinally, by a fine saw. In the opening, so formed, he placed diamond powder, securing it in its situa

first series of the Annals of Philosophy. It is full of important matter, and contains in few words the results of a great number of observations; and, with his second paper, comprises a very large part of the facts that are as yet known relating to this subject.

317. Upon the excitation of the Voltaic apparatus, by the proper arrangement of its plates and fluid, it is known that certain powers are given to its poles or extremities which enable them, when attached to an electrometer, to show by their divergence a certain tension of electricity; or when connected together by fluids, wires, or other conducting substances, to decompose or heat them. These effects have been known for several years, and are generally attributed to electricity produced by the apparatus; the effects of tension belonging to the insulated state of the poles; those of decomposition and heating to their connected state.

318. When the two poles of such a battery or apparatus are connected by conductors of electricity, the battery is discharged; that is, the tension of the electricity at the poles is lessened, and that, according as the conducting power of the substance is more or less powerful. Good conductors, discharge it entirely and instantly; bad conductors with more or less difficulty; but as the instrument has within itself the power of renewing its first state of tension on the removal of the conducting medium, and that in a very short space of time, it is evident that the connecting substance is continually performing the same office during the whole time of its contact that it did at the first moment, and this whether it be a good or a bad conductor; and it is also evident that it must be in a different state in this situation than when separated from the apparatus. It is important at present rather to consider the action of a good conductor in discharging the battery, as the phenomena to be considered are in that case more energetic. A metallic wire, therefore, may be used to connect the two poles; it will discharge a powerful apparatus; and, consequently, whatever takes place in the connecting medium is here compressed into a very small place. Those who consider electricity as a fluid, or as two fluids, conceive that a current or currents of electricity are passing through the wire, during the whole time it forms the connexion between the poles of an active apparatus. There are many arguments in favor of the materiality of electricity, and but few against it; but still it is only a supposition; and it will be as well to remember, while pursuing the subject of electro-magnetism, that we have no proof of the materiality of electricity, or of the existence of any current through the wire.

319. Whatever be the cause which is active within the connecting wire, whether it be the passage of matter through it, or the induction of a particular state of its parts, it produces certain very extraordinary effects. If small, it be comes heated; and as the size of the wire is diminished, or that of the apparatus increased, the heat rises to an intense degree apparently without any limitation, except from the influence of external circumstances, or the alteration of the wire. Another effect, and it is that to which

M. Oersted, here calls attention is, that, if brought towards a magnetic needle, it has the power of attracting and repelling it in a constant manner, and in obedience to certain simple laws. 320. If a magnetic needle be left to take its natural direction, and then a straight portion of the connecting wire be brought above it, and parallel to it, that end of the needle next the negative pole of the battery moves towards the west; and that whether the wire be on the one or the other side of the needle, so that it be above and parallel to it. If the connecting wire be sunk on either side the needle, so as to come into the horizontal plane in which the needle is allowed to move, there is no motion of the needle in that plane; but the needle attempts to move in a vertical circle; and but for the imperfect suspension, and the influence of the earth's magnetism, would do so. When the wire is on the east of the needle, the pole of the needle next the negative end of the battery is elevated; and when on the west of the needle it is depressed. If the connecting wire be now sunk below the level of the needle, similar attractions and repulsions take place, but in opposite directions to those followed when it is above. The pole of the needle opposite the negative end of the battery now moves eastwards, whatever the position of the wire, so that it be restricted as above.

321. That these positions of the magnetic needle may be retained with more facility in the memory, professor Oersted proposed the following formula: The pole above which the negative electricity enters is turned to the west; under which, to the east.'

322. M. Oersted subsequently pointed out, what it is easy to see from the above experiments, that the movement of the needle took place in a circle round the connecting wire; and though, in the description of his first experiments, the quantity of declination given to the needle from the wire is expressed by an angle of so many degrees, yet it is afterwards stated to vary with the power of the battery. Whenever the needle is moved in a horizontal or any other circle from the position it naturally assumes, the power of the earth over it tends to restore that position, and is consequently an active force in the present instance opposed to the power of the connecting wire; it therefore lessens the declination the needle would otherwise have. Also when the wire is brought into the same horizontal circle with the needle, its effect over it is shown by the elevation and depression of its opposite ends; and it is the mode of suspension combined with the earth's magnetic power that prevents it from traversing in a vertical circle. But if those interfering circumstances be removed, viz. if the suspension be such as to allow of free motion to the needle in every direction, and the earth's magnetism be rendered null, or counteracted either by the position of the needle, or by the vicinity of another magnet, then a much simpler idea of the relative movements of the wire and needle may be obtained.

323. It is not, perhaps, easy to obtain this perfect state of apparatus, but it is not difficult so to arrange it as to examine the movements first

in one direction, and then in another. It will then be found, if the connecting wires of a suthciently powerful apparatus he placed near a magnetic needle so as to pass near its centre, that the needle will arrange itself directly across the wire, whatever the previous position of the two; that if the wire be carried round the centre of the needle, or the centre of the needle found the wire, the same relative position of the two will continue; and that the direction of the needle across the wire is not indifferent, but has its poles always in a constant position to the poles of the battery. If the positive pole of a battery be on the right hand, and the negative pole on the left, and a wire be stretched between, connecting them, then a needle above the wire will point the north pole from, and the south towards us; or if below, the south pole from, and the north towards the experimenter. See fig. 5, plate II. 324. If the connecting wire and the needle be represented by two small rods named accordingly, and fastened permanently together, then they will represent the wire and the needle in all positions; for, however one be placed, the other will correspond with it: or if, on the under side of a small square piece of glass, a line be drawn from top to bottom, the upper end being called negative, and the lower positive; and on the upper surface a line be drawn from left to right, the left termination being named south, the right north; then the lower line will always represent the connecting wire, and the upper the needle. Fig. 6.

325. The needle and wire being in this position, if the wire be moved along the needle towards either extremity, strong attractions will take place between it and the pole, notwithstanding the same part of the wire be employed; and the poles in the two positions are contrary to each other. In this case it appears that the same point in the wire has the power of attracting both the north and south pole of the needle. If while the wire is thus situated near the end of the needle, the latter be turned round, so that the pole before there be replaced by the oppo-, site pole, strong repulsions will take place; and that to whichever pole the wire has in the first instance been carried, so that the same point which before attracted both poles will now repel them both. If, when the wire is near the extremity of the needle where the attraction is strongest, it be moved round the end so as to go from one side to the other, keeping the same point constantly towards the needle, its attractive power over the needle will be found to increase as it approaches the end, but remains on one side of it; will diminish as it turns the end; will be come null when exactly opposed to the pole; and, as it passes on the other side, will resume repulsive powers, which will be strongest at the extremity of the pole on the opposite side to where the wire was situated at first. Fig. 7.

326. In all these cases the positions assumed by the wire and needle, whether the result of atfraction or repulsion, are the same as those before described, except that the wire is now near the end of the needle instead of the middle; and it will be found that all the attractions and repulsions may be reduced to four positions of the

needle to the wire, in which it forms tangents with it. In fig. 8, the north pole; in fig. 9, the south pole; if in either of them the poles of the needle be reversed, the tangents remaining in the same direction, repulsion will take place. Hence it is easy to see how any individual part of the wire may be made attractive or repulsive of either pole of the magnetic needle by mere change of position:

327. The magnetic property does not depend upon the metal employed or its form, but is exerted by any of them which forms the circuit between the poles: even a tube filled with mercury is effectual: the only difference is in the quantity of effect produced. It continues also, though the conductor be interrupted by water, unless the interruption be of great extent.

328. The magnetic influence of the wire extends through all sorts of substances, and acts on the needle beyond, just as in cominon magnetism. It does not act on needles of brass, glass, or gum lac.

329. In a second paper on this subject, M. Oersted shows that not intensity, but quantity, is wanting in the Voltaic apparatus, to produce this effect most eminently. A single galvanic arc is sufficient for the purpose. A plate of zinc, six inches square, placed in a trough of copper, filled with diluted acid, enabled the wire which connected the two metals to act powerfully; and, with a similar arrangement, the zinc plate having a surface of 100 square inches, an effect was produced on the needle at the distance of three feet. He also, in this paper, describes the construction of a Voltaic combination so light, that being suspended, it moved on the approach of a magnet: the motions were in accordance with what has been said, and may easily be conceived.

330. The results obtained by M. Oersted were immediately repeated and confirmed by a great number of philosophers in various places. Of these no one was more active than M. Ampere, in varying experiments, making new ones, and applying to them the most judicious theory.

331. The facts discovered by M. Ampere, though not numerous, are of great importance. He described an experiment, proving that the Voltaic pile itself acted in the same manner as the wire, connecting its two poles; and constructed an instrument which, at the same time that it proved this action, was found to be of great use in experiments on currents of electricity. This was merely a magnetic needle, but from the uses to which it was applied was called a galvanometer. When placed near a pile, or trough, in action, having its poles connected either by a wire, or by introducing them into one cell, it immediately moved, becorning obedient to the battery in the same manner as to the connecting wire; and the motions were such as if the battery were simply a continuation or part of the wire. In consequence of this action, the needle becomes an instrument competent to indicate that state of an active Voltaic pile, and the wire connecting it, which is supposed to be occasioned by currents of electricity, and in which only, magnetism. has yet been most perfectly discovered.