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ment. None of the ordinary practices judiciously melted at the point of contact. In a subsequent erijomed by the Humane Society, should ever, on experiment, the zinc did not melt; but the plasuch occasions, he neglected. For it is surely tina ignited as before. criminal to spare any pains which may contribute, 273. Experiment VII.-Zinc and iron. The in the slightest degree, to recall the fleeting iron was ignited : the zinc bore the heat without breath of man to its cherished mansion.'

fusing. 266. We have hitherto confined ourselves to 274. Experiment VIII.-Lead and platina. the effects of small batteries, but we must not The lead fused at the point of contact. omit to notice the powerful Voltaic apparatus 275. Experiment IX.-Tin and platina. The constructed by Mr. Children, as well as the re- tin fused at the point of contact. No ignition of sults obtained by it, or the more portable as well either wire took place in the two last experias powerful arrangement by Mr. Pepys. In the ments. first of these arrangements, the copper and zinc 276. Experiment X.-Zinc and silver. The plates of the apparatus were connected together, zinc was ignited before it melted : the silver in the usual order, by leaden straps, six feet long was not ignited. by two feet eight inches broad, each plate pre 277. The results in every case were the same senting thirty-two square feet of surface. All the to whichever pole of the battery either wire was plates being attached to a strong wooden frame presented. These experiments were varied by suspended by ropes and pulleys, which, being introducing several alternations of different wires balanced by counterpoises, was easily lowered continuously connected, into the circuit, and and elevated, so as to immerse the plates in the obtained in every instance analogous results. acid, or raise them out of it at pleasure. The Thus, cells of the battery were twenty-one in number, 278. Experiment XI.-Alternations of platina and their united capacities amounted to 945 gal- and silver, three times repeated : all the platina lons. To each pole of the battery a leaden pipe, wires were ignited, and none of the silver about three-fourths of an inch in diameter, was 279. Experiment XII.--One zinc wire beattached by solder, and the opposite end of each tween two platina : both the platina wires were pipe immersed in a basin of mercury (a separate ignited, the zinc not. baxia for each pipe), by means of which the cir 280. Experiment XIII.--One iron between cuit was completed, and a perfect contact ensured. two platina. Both the latter first ignited; then The battery was afterwards improved at the sug- the iron, which soon became fully heated, and gestion of Dr. Wollaston, and the copper coiled fused. completely round each zinc surface. See fig. 3, 281. It is unnecessary to enter into a farther plate II. The first experiments we shall mention detail of these experiments; it will be sufficient were made on the comparative facility with which to say generally, that when wires of several difdifferent metals are ignited when placed in the ferent metals were introduced at once into the electrical circuit. For this purpose, in each ex- circuit, the order of their ignition was precisely periment, two wires of dissimilar metals were that of the former experiments. In one experitaken, of equal diameter and length; one end of ment the copper was decidedly most heated. each was in contact with one of the basins of 282. To explain these phenomena, Mr. Chilmercury communicating with the poles of the dren supposes that when a perfect communicabattery, and the other end bent to an angle, and tion is established between the poles of the the wires connected continuously by hooking battery, the electricity circulates withont producthem together. The length of each wire was ing any visible effect; but, if it meet with resisteight inches, and the diameter one-thirtieth of an ance in its passage, it manifests itself by chemiinch. The battery was moderately excited by a cal action, by the evolution of heat, or both. charge of one part acid diluted with forty parts Thus, if a bar of metal be connected with one of water.

pole of the battery, and its extremity immersed 267. Experiment I.-A platina and a gold in a basin of mercury connected with the other wire being thus connected, and introduced into pole, at the instant the surfaces come in contact, the electrical circuit, the platina was instantly heat and light are evolved, which cease as soon ignited, the gold remained unaffected.

as the bar, if it be of sufficient size, is fairly 268. Experiment II.-A similar arrangement plunged beneath the surface of the quicksilver. of gold and silver wires. The gold was ignited, If the circuit be completed by two pieces of the silver not.

charcoal, the evolution of heat and light is per269 Experiment III.—The same with gold manent, as long as their surfaces remain in conand copper. No perceptible difference in the tact, because that contact can never be so perstate of ignition; both metals were heated red. fect, as to oppose no resistance to the electricity;

270. Experiment IV.-Gold and iron. The whereas, in the case of the bar of metal and the iron was ignited ; the gold unchanged.

mercury, it soon becomes complete, and the cur271. Experiment V.–Platina and iron. The rent is then uninterrupted. Resistance, thereIron ignited instantly at the point of contactfore, appears to occasion the development of next the pole of the battery. Then the platina heat (whatever be the ultimate cause of the became ignited through its whole extent. After phenomenon), and as this must be inversely as this the iron became more intensely heated than the conducting power, when any two of the he platina, and the ignition of the latter de- wires connected continuously are placed in the Teased.

circuit, that which is the worst conductor must 272. Experiment VI.- Platina and zinc. The be most heated; and thus platina, having the platina was ignited : the zinc was not; but lowest conducting power, is ignited before all

the rest; and silver, which conducts best, is not 296. Experiment VII.--Compound ore of heated red when connected with any of the other iridium and osmium; fused into a globule. metals.

297. Experiment VIII.-Pure iridium; fused 283. The following experiments were made into an imperfect 'globule, not quite free from with the battery in a high state of excitation; small cavities, and weighing 7.1 grains. The and Mr. Children considers them as represent- metal is white, very brilliant, and in its present ing nearly the maximum of effect which it is ca state its specific gravity is 18.68, which must be pable of producing. As the quantity of acid much too low, on account of the porous state was increased from time to time, and that pre- of the globule. In the Minutes of the Experiviously added often almost spent before fresh ments, in July 1813, mention is made of the was put in, it is not easy to say exactly what fusion of a small portion of pure iridium into a proportion it bore to the water; perhaps the globule weighing home of a grain, which had been largest may be stated at about sth. On this, as previously submitted to the action of a battery on former occasions, he found a mixture of 'ni- of 2000 plates, of four inches square, without trous and sulphuric acids, to produce the most melting. powerful and permanent effects.

298. Experiment IX.—Ruby and sapphire, 284. Experiment 1.-Five feet six inches of were not fused. platina wire, tot of an inch in diameter, were 299. Experiment X.-Blue spinal ran into a neated red throughout, visible in full daylight. slag.

285. Experiment II.-Eight feet six inches of 300. Experiment XI.-Gadolinite, fused into platina wire, il of an inch in diameter, were globules. heated red.

301. Experiment XII.-Magnesia was ag286. Experiment III.-A bar of platina of glutinated. an inch square, and 21 inches long, was also 302. Experiment XIII.—Zircon from Norheated red, and fused at the end; and,

way was imperfectly fused. 287. Experiment IV.-A round bar of the 303. Experiment XIV.-Quartz, silex, and same metal, més of an inch in diameter, and 24 plumbago, were not affected. inches long, was heated bright red throughout. 304. In the year 1796 M. Clouet converted

288. Experiment V.-Fine points of box- iron into steel, by cementation with the diamond, wood charcoal intensely ignited in chlorine, with the view of confirming the nature of that neither suffered any change, nor produced any substance, and of ascertaining the exact state in in the gas. The result was similar when beated which carbon exists in steel. Clouet had also in azote.

previously formed steel by cementation with car289. Mr. C. next tried the power of the bat- bonate of lime. Mr. Mushet repeated this extery to fuse several refractory substances. The periment, using, instead of the carbonate, caustic subject of experiment was placed in a small sime, and obtained also what he considered to cav ty, made in a piece of well burnt boxwood be cast sieel; whence he concluded that the carcharcoal, Hoating on the surface of the mercury bon necessary to convert the iron into steel had in one of the basins before mentioned, and the not been furnished, as Clout supposed, by decircuit completed by another piece of charcoal, composition of the carbonic acid, but that it had conmunicating by stout copper wire with the found its way from the ignited gas of the furnace other basin.

to the iron. This result occasioned suspicions 230. Experiment I.–Oxide of tungsten, which of the accuracy of the de uctions from the ex(as well as other metallic oxides operated on) periment with the diamond; and Mr. Mushet had been previously intensely ignited in a char- accordingly, at the suggestion of the editor of coal crucible, in a powerful furnace, fused, and the Philosophical Magazine, repeated the experiwas partially reduced. The metal grayish white, ment made at the Polytechnic School, only keepheavy, brilliant, and very brittle.

ing out the diamond. The results (for he made 291. Experiment II.–Oxide of tantalum. A several experiments), uniformly gave him good very small portion fused. The grains have a cast steel, whence he concludes that we are still reddish-yellow color, and extremely brittle. without any satisfactory or conclusive proof of

292. Experiment III. --Oxide of uranium; the steelification of iron solely by means of the fused, but not reduced.

diamond;

and adds that he doubts whether the 293. Experiment IV.–Oxide of titanium; diamond afforded even one particle of carbon to fusel, not reduced. When intensely heated, it the iron. The details of both Clouet's and Muburnt, throwing off brilliant sparks like iron. shet's experiments, may be found in the fifth vo

294. Experiment V.–Oxide of cerum; fused, lume of the Philosophical Magazine. Sir George and when intensely heated it burnt with a large, M'Kenzie repeated both results confirming the vivid white flame, and was partly volatilised, conclusions of the French chemist. The labors but not reduced. The fused oxide, on expo- of this gentleman would at first view appear consure for a few hours to the air, fell into a light clusive; but, if a doubt should remain, it occurred brown powder, containing numerous shining to Mr. Pepys, that the battery would afford an particles of a silvery lustre interspersed amongst experimentum crusis on the subject; and his init, and exhaled an odor, similar to that of phos- geruity readily sug ested a mode of making it, phureted hydrogen.

every way unobjectionable. He bent a wire of 295. Experiment VI.–Oxile of molybdena; pure soft iron, so as to form an angle in the midreadily fused and relucel. The metal is very dle, in which part he divided it longitudinally, brittle, of a steel gray color, an l soon becomes by a fine saw. In the opening, so forined, he covered with a thin coat of purple oxide. placed diamond powder, securing it in its situa

tion by two finer wires, laid above and below.it, tral axis at the top of the upright piece of timber. and kept from shifting, by another small wire, 310. The coil consists of two plates, each fifty bound firmly and closely round them. All the feet in length and two feet in width; the one copwires were of pure soft iron, and the part con- per, and the other zinc, making a superficial surtaining the diamond powder was enveloped by face of 400 feet. They are rolled or wrapped thin leaves of talc. Thus arranged, the appara- round a cylinder of wood, with three strands or tus was placed in the electrical circuit, when it ropes of horse-hair between each plate, to presoon became red hot, and was kept so for six vent contact of the metals; and, to maintain these minutes. The ignition was so far from intense, in their situation, notched sticks are occasionally that few who witnessed the experiment expected introduced in the rolling. Two conductors of any decisive result. On opening the wire, how- copper, near three-fourths of an inch in thickness, ever, Mr. Pepys found that the whole of the are firmly attached to the end of each plate, from diamond had disappeared; the interior surface which the power is dispensed upon immersion in of the iron had fused into numerous cavities, the acid. notwithstanding the very moderate heat to which 311. Rather more than fifty gallons of dilute it had been exposed; and all that part which had acid are requisite to charge the receptacle inbeen in contact with the diamond was converted tended for the metallic spiral ; and, to put the into perfect blistered steel. A portion of it being apparatus in operation, the coil is gradually heated red, and plunged into water, became so lowered into the tub beneath. The immersion of hard as to resist the file, and to scratch glass. the spiral, however, displaces a certain portion of This result is conclusive; for as the contact of water ; so that it is necessary to restore the equiany carbonaceous substance, except the included librium by withdrawing one of the balancediamond, was effectually guarded, to that alone weights. In the apparatus actually employed can the change produced in the iron be referred. in the theatre of the London Institution, there is This experiment will also probably be deemed but one tub employed; but in the improved fatal to the opinion of those mineralogists (if any form, represented in the diagram, it may be redo still maintain that opinion), who class the moved to a vessel of water, and its maximum diamond with substances of the siliceous genus. effect produced by a subsequent immersion in

305. When dry caustic potassa was exposed the dilute acid. to the intense heat between the two pieces of 312. As a mere electrical battery, the effect to charcoal, it fused, and appeared to decompose, be derived from this pair of plates is comparathrowing off a large flame of the peculiar purple tively small; but its powers as an agent for illuscolor, that attends the combustion of potassium. trating the connexion between magnetism and When moist caustic potassa was placed in the electricity are truly astonishing. circuit, the water only was decomposed.

313. Magnetic needles, placed at a distance of 307. The second apparatus was constructed several feet from the apparatus, were readily put under the immediate direction of Mr. Pepys for into motion, and deflected from their previous the London Institution, and the great portability position. The most singular phenomenon, howof this gigantic galvanic spiral gives it an especial ever, which resulted from the series of expericlaim to the notice of the scientific world. The ments with this extraordinary instrument, remains apparatus is shown at fig. 4.

to be noticed :-A spiral of wire was connected 308. The two inbs, T, T, are somewhat larger with the two poles of the battery shown at C,C, than the metallic coil. The one beneath the and, being placed in a perpendicular direction, weight is intended as a receptacle for water, a steel cylinder was dropped from the upper end, while the other is charged with dilute acid. and this, instead of obeying the ordinary laws of

309. The spiral M is suspended hy a cord, gravitation, was found, after a few oscillations, and balanced hy the weight W; the beam over to take a position somewhere midway between which the cord passes being moveable on a cen- the two extremities of the tube.

ELECTRO-MAGNETISM.

314. The connexion between galvanism and Copennagen, was for many years engagea in magretism m'ist now he examined. The term enquiries respecting the identity of chemical, electro-magnetism has been employed to desig- electrical, and magnetic forces; and, as early as nate a science which has originated since the 1807, proposed to try · whether electricity the commencement of the present century, and which most latent had any action on the magnet. At has received no ordinary attention from the con- that time no experimental proofs of the peculiar tiner.tal philosophers, as well as from those of opinions he entertained were known; but his our own country. Amongst those who have constancy in the pursuit of bis object, both by done most towards the development of electro- reasoning and experiment, was well rewarded in magnetism, we may especially enumerate M. the winter of 1819, by the discovery of a fact o Oersted, Sir Humphry Davy, and professor which no previous notice had been taken; but Barlow, and the latter of these gentlemen has which, when once known, instantly drew the prblished a very valuable work illustrative of attention of all those who were at all able to apthe science.

preciate its importance and value. 315. M. Oersted, professor of natural philo 316. M. Oersted's own account of this dis sophy, and secretary to the Royal Society of very has been published in volume xvi. of the Vol. VII.

I

first series of the Annals of Philosophy. It is M. Oersted, here calls attention is, that, if full of important matter, and contains in few brought towards a magnetic needle, it has the words the results of a great number of observa- power of attracting and repelling it in a constant tions; and, with his second paper, comprises a manner, and in obedience to certain simple laws. very large part of the facts that are as yet known 320. If a magnetic needle be left to take its relating to this subject.

natural direction, and then a straight portion of 317. Upon the excitation of the Voltaic appa- the connecting wire un brought above it, and ratus, by the proper arrangement of its plates and parallel to it, that end of the needle next the neHuid, it is known that certain powers are given tive pole of the battery moves towards the to its poles or extremities which enable them, west; and that whether the wire be on the one when attached to an electrometer, to show by or the other side of the needle, so that it be their divergence a certain tension of electricity; above and parallel to it. If the connecting wire or when connected together by fluids, wires, or be sunk on either side the needle, so as to come other conducting substances, to decompose or into the horizontal plane in which the needle is heat them. These effects have been known for allowed to move, there is no motion of the needle several years, and are generally attributed to in that plane; but the needle attempts to move electricity produced by tl'e apparatus ; the effects in a vertical circle; and but for the imperfect of tension belonging to the insulated state of the suspension, and the influence of the earth's poles; those of decomposition and heating to magnetism, would do so. When the wire is on their connected state.

the east of the needle, the pole of the needle 318. When the two poles of such a battery or next the negative end of the battery is elevated ; apparatus are connected by conductors of elec- and when on the west of the needle it is de tricity, the battery is discharged; that is, the pressed. If the connecting wire be now sunk tension of the electricity at the poles is lessened, below the level of the needle, similar attractions and that, according as the conducting power of and repulsions take place, but in opposite directhe substance is more or less powerful. Good tions to those followed when it is above. The conductors, discharge it eatirely and instantly; pole of the needle opposite the negative end of bad conductors with more or less difficulty; but the battery now moves eastwards, whatever the as the instrument has within itself the power of position of the wire, so that it be restricted as renewing its first state of tension on the removal above. of the conducting medium, and that in a very 321. That these positions of the magnetic short space of time, it is evident that the con- needle may be retained with more facility in the necting substance is continually performing the memory, professor Oersted proposed the following same office during the whole time of its contact formula : "The pole above which the negative that it did at the first moment, and this whether electricity enters is turned to the west; under it be a good or a bad conductor; and it is also which, to the east.' evident that it must be in a different state in this 322. M. Oersted subsequently pointed out, situation than when separated from the apparatus. what it is easy to see from the above experiments, It is important at present rather to consider the that the movement of the needle took place in a action of a good conductor in discharging the circle round the connecting wire; and though, battery, as the phenomena to be considered are in the description of his first experiments, in that case more energetic. A metallic wire, the quantity of declination given to the needle therefore, may be used to connect the two poles; from the wire is expressed by an angle of so many it will discharge a powerful apparatus ; and, degrees, yet it is afterwards stated to vary with consequently, whatever takes place in the con the power of the battery. Whenever the needle necting medium is here compressed into a very is moved in a horizontal or any other circle from small place. Those who consider electricity as the position it naturally assumes, the power of a fluid, or as two fluids, conceive that a current the earth over it tends to restore that position, or currents of electricity are passing through the and is consequently an active force in the prewire, during the whole time it forms the con sent instance opposed to the power of the connexion between the poles of an active apparatus. necting wire; it therefore lessens the declination There are many arguments in favor of the mate- the needle would otherwise have. Also when riality of electricity, and but few against it; but the wire is brought into the same horizontal circle still it is only a supposition; and it will be as with the needle, its effect over it is shown by the well to remember, while pursuing the subject of elevation and depression of its opposite ends; electro-magnetism, that we have no proof of the and it is the mode of suspension combined with materiality of electricity, or of the existence of the earth's magnetic power that prevents it from any current through the wire.

traversing in a vertical circle. But if those inter319. Whatever be the cause which is active furing circumstances be removed, viz. if the suswithin the connecting wire, whether it be the pension be such as to allow of free motion to the passage of matter through it, or the induction needle in every direction, and the earth's magof a particular state of its parts, it produces cer- netism be rendered null, or counteracted cither tain very extraordinary effects. If small, it be- by the position of the needle, or by the vicinity comes heated ; and as the size of the wire is of another magnet, then a much simpler idea of diminished, or that of the apparatus increased, the relative movements of the wire and needle the heat rises to an intense degree apparently may be obtained. without any limitation, except from the influence 323. It is not, perhaps, easy to obtain this of external circumstances, or the alteration of perfect state of apparatus, but it is not difficult the wire. Another effect, and it is that to which so to arrange it as to examine the movements first

la one direction, and then in another. It will needle to the wire, in which it forms tangents then he found, if the connecting wires of a with it. In fig. 8, the north pole; in fig. 9, the sufficiently powerful apparatus he placed near a south pole ; if in either of them the poles of the magnetic needle so as to pass near its centre, needle be reversed, the tangents remaining in that the needle will arrange itself directly across the same direction, repulsion will take place. the wire, whatever the previous position of the Hence it is easy to see how any individual part two; that if the wire be carried round the centre of the wire may be made attractive or repulsive of the needle, or the centre of the needle round of either pole of the magnetic needle by mere the wire, the same relative position of the two change of position. will continue; and that the direction of the needle 327. The magnetic property does not depend across the wire is not indifferent, but has its poles upon the metal employed or its form, but is exalways in a constant position to the poles of the erted hy any of them which forms the circuit battery. If the positive pole of a battery be on between the poles: even a tube filled with merthe right hand, and the negative pole on the left, cury is effectual : the only difference is in the and a wire be stretched between, connecting quantity of effect produced. It continues also, them, then a needle above the wire will point though the conductor be interrupted by water, the north pole from, and the south towards us; or unless the interruption be of great extent. if below, the south pole from, and the north 328. The magnetic influence of the wire extowards the experimenter. See fig. 5, plate II. tends through all sorts of substances, and acts

324. If the connecting wire and the needle be on the needle beyond, just as in cominon magrepresented by two small rods named accord- netism. It does not act on needles of brass, ingly, and fastened permanently together, then glass, or gum lac. they will represent the wire and the needle in all 329. In a second paper on this subject, M. positions; for, however one be placed, the other Oersted shows that not intensity, but quantity, is will correspond with it: or if, on the under side wanting in the Voltaic apparatus, to produce of a small square piece of glass, a line be drawn this effect most eminently. A single galvanic from top to bottom, the upper end being called arc is sufficient for the purpose. A plate of zinc, negative, and the lower positive; and on the six inches square, placed in a trough of copper, upper surface a line be drawn from left to right, filled with diluted acid, enabled the wire which the left termination being named south, the right connected the two metals to act powerfully; and, Lorth; then the lower line will always represent with a similar arrangement, the zinc plate having the connecting wire, and the upper the needle. a surface of 100 square inches, an effect was Fig. 6.

produced on the needle at the distance of three 325. The needle and wire being in this posi- feet. He also, in this paper, describes the contion, if the wire be moved along the needle to- struction of a Voltaic combination so light, that wards either extremity, strong attractions will being suspended, it moved on the approach of a take place between it and the pole, notwithstand- magnet: the motions were in accordance with ing the same part of the wire be employed; and what has been said, and may easily be conthe poles in the two positions are contrary to each ceived. other. In this case it appears that the same 330. The results obtained by M. Oersted were point in the wire has the power of attracting immediately repeated and confirmed by a great hoth the north and south pole of the needle. If number of philosophers in various places. Of while the wire is thus situated near the end of these no one was more active than M. Ampere, the needle, the latter be turned round, so that in varying experiments, making new ones, and the pole before there be replaced by the oppo-, applying to them the most judicious theory. site pole, strong repulsions will take place; and 331. The facts discovered by M. Ampere, that to whichever pole the wire has in the first though not numerous, are of great importance. instance been carried, so that the same point He described an experiment, proving that the which before attracted both poles will now repel Voltaic pile itself acted in the same manner as the them both. If, when the wire is near the extre- wire, connecting its two poles; and constructed mity of the needle where the attraction is an instrument which, at the same time that strongest, it be moved round the end so as to go it proved this action, was found to be of from one side to the other, keeping the same great use in experiments on currents of elecpoint constantly towards the needle, its attractive tricity. This was merely a magnetic needle, power over the needle will be found to increase but from the uses to which it was applied as it approaches the end, but remains on one side was called a galvanometer. When placed near of it; will diminish as it turns the end; will be a pile, or trough, in action, having its poles come null when exactly opposed to the pole; connected either by a wire, or by introducing and, as it passes on the other side, will resume them into one cell, it immediately moved, berepulsive powers, which will be strongest at the coming obedient to the battery in the same extremity of the pole on the opposite side to manner as to the connecting wire; and the mowhere the wire was situated at first. Fig. 7. tions were such as if the battery were simply a

326. In all these cases the positions assumed continuation or part of the wire. In consequence by the wire and needle, whether the result of at- of this action, the needle becomes an instrument fraction or repulsion, are the same as those be- competent to indicate that state of an active Volfore described, except that the wire is now near taic pile, and the wire connecting it, which is the end of the needle instead of the middle; and supposed to be occasioned by currents of elecit will be found that all the attractions and re- tricity, and in which only, magnetism. has yet pulsions may be reduced to four positions of the been most perfectly discovered.

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