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M'GAULEY'S LOCOMOTION BY GALVANISM.

distance from the iron, its action is nothing, -in some cases, perhaps, as we shall see, even injurious. The effective distance of the helix from the iron cannot be great, since its action, probably, decreases in the inverse proportion of the square of that distance. This difficulty cannot be obviated, as some have imagined, by causing the electrical currents to circulate through the mass of iron, uniting together a number of coiled bars. This would present an arrangement probably similar to a permanent magnet, the masses of iron acting on each other by induction, the reversion of the poles would be very slow, or altogether impossible. The action of the magnets, rather than their masses, must be united; but in this new difficulties occur. Their action must be simultaneous, or the machinery will be broken, or ineffective; the time after reversion, and during which a bar can be thrown off a magnet, is extremely short-hence one reason why it is difficult to unite the action of several magnets. But let us suppose that we have obtained a simultaneous reversion of the poles and throwing off of the bars-a thing totally impossible, he conceived, from the number and complication of circumstances by which it is influenced-how shall this action be applied to machinery? If the fly-wheel of a steamengine, from the shutting off of the steam, be not impelled by the engine while it continues in motion, it drags the piston, uninjured, through the cylinder; but suppose something to retain the piston in one position, without stopping the wheel, the effect were highly injurious-this is exactly what must frequently happen in electro-magnetism. It is impossible to reverse the poles even of one magnet, in such a manner that the position of the bars shall always correspond with the position of the crank and fly-wheel.

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causing half the revolutions of the crank C'X, while B is moving, so that its extremity shall be at P'; then C'X shall have become C' X" while it is going to P", C'X' shall become C' X", but if when the crank C/X is in the position of C'X"", one of the dead points, the bar is not ready to leave M'; or, in other words, if the magnet which holds it be not ready at once to send it offa thing very probable-the fly-wheel continues to revolve by its own inertia, and the machinery is broken, or the bar is torn from the magnet, which often has a curious and perplexing effect on the reversion of the poles.

A better reversing apparatus was to be obtained. The one of last year, though perfectly successful, required the agency of mercury, which, for many reasons, is objectionable; it becomes oxidated, then contact is imperfect, and the level in the cups, which is of the last importance, is destroyed: it is liable to a thousand accidents, not to speak of its destroying the wires of the apparatus itself.

Again, the form of the apparatus, whether mercury be used or not, must be changed, and the principle of the one now exhibited to the Section adopted, since the apparatus, which will reverse the poles of one magnet, will not with speed or certainty reverse the poles of two or more, when worked by the engine itself. The apparatus shown to the Section had been used with great success in the reversion of the poles of four powerful magnets.

The attachment of the reversing apparatus to the machine becomes difficult, when more than one magnet is used, for reasons with which he would not then occupy the Section. He believed he might mention, that he possessed an engine of considerable power, in which these difficulties were overcome.

The experiments he should detail to the Section were numerous and complicated; he had taken every means to secure their accuracy; some of them appear anomalous, but were undoubtedly modified by circumstances, many of which are so obscure, that he has not been able yet to detect them. He remarked, that it was obviously important to make experiments in considerable number, and on a large scale, since the former secures a greater accuracy, the latter the notice of results which, from their minuteness, might otherwise escape observation. His inquiries resolved themselves into two points-the nature of magnetism-the best means of producing it. The means of overcoming the difficulty arising from the necessarily limited size of the iron and the helix, he might probably treat at a future period.

[Mr. M'Gauley then entered into a detail of his experiments.]

Mr. M'Gauley thought it would be un

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M'GAULEY'S LOCOMOTION BY GALVANISM,

becoming in him to suggest any thing to the British Association; but he believed nothing would be more conducive to the interests of science, than that the Association should cause to be instituted a series of experiments on the galvanic battery and its charge, which would set all questions on the matter at rest for ever. Before he left this part of the subject, he thought it well to recall the attention of the Section to the nature of the power obtained by electro-magnetism. In steam, one great cause of the varying power of the engine arises from the varying leverage of the crank. Let B and B' be positions of the extremity of the piston-rod, C'R and C'R' corresponding positions of the crank, the leverage of the crank is measured by the perpendicular C'P and C'P'. It varies as that perpendicular. But in electro-magnetism, the force at B, say the bar traversing between the magnets, is always varying. He would not then enter into some curious results obtained by calculation on this matter.

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He had been anxious to satisfy himself, by his own experiment, of the truth of the law of magnetic attraction being in the proportion of the inverse square of the distance, but abandoned the inquiry for the present, when he found that a magnet, with a seemingly appropriate bar, would lift at onesixteenth of an inch only five pounds; though with a different bar it lifted the same weight at twelve times the distance; and that the greater the distance through which powerful attraction might be exerted, the less the lifting power appeared.

In examining the identity of electricities derived from different sources, it seemed to Mr. M'Gauley that we sometimes forget that electricity may be modified both as to quantity and intensity; and that if either be changed, or both, we cannot expect the same results. To test, therefore, the identity of any agent with electricity, we must not use those means which are the measure of, or dependent on, either quantity or intensity; for if in such experiments the electrometer or galvanometer be not affected, we only arrive

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at a negative conclusion-that if the agent under consideration be electricity, it differs from the ordinary electricity in quantity, intensity, or both. For though we never had been able with galvanism to cause the leaves of the electrometer to diverge, or with machine electricity to deflect the galvanometer, or with electricity to produce magnetism, or with magnetism, electricity, with electricity to produce heat, with heat, electricity,—their non-identity would by no means follow. To examine with ease and certainty the identity of any thing with electricity, we must find some property of electricity, which is not modified by, nor dependent on, quantity or intensity. We know, and chemistry furnishes us with one proof, that the elements of things may be the same as to quantity, and as to the intensity of mutual action; and yet may be productive of vastly different effects. Thus we know, that from two equal volumes of carbon and hydrogen, may be formed at least three very different substances.

The following facts seem to afford additional evidence of the perfect identity of electricity and magnetism; and that magnetism does not require, nor suppose, the circulation of electrical currents.

1st. A shock and spark are obtained by means of an electro-magnet only after battery communication is broken; for no matter how R long this communication is maintained, neither shock nor spark shall be perceived. 2ndly. The shock and spark are not the effects of the battery; for to obtain a shock

(this shock he had not seen remarked by any experimentalist)-it is not necessary to form a part of the communication between the copper and zinc, but merely between the extremities of the helix, or between either extremity of the helix and the copper or zinc of the battery. 3rdly. The shock and spark do not arise from the magnetism of the bar included in the helix, since the more perfectly the bar is de-magnetised in breaking contact the better. Besides, it is curious that a powerful shock and brilliant spark may be obtained without any iron, and from a heap of wire thrown without any heliacal arrangement. This, Mr. M'Gauley remarked, would lead to a very simple and effective electrical apparatus, one easily managed, and always ready for use; the length and number of the coils, with a given calorimeter, has an effect on the shock and spark. Mr. M'Gauley exhibited to the Section wire coiled with the greatest accuracy, by a machine he had constructed, which was capable of covering any wire, manufacturing pianoforte strings, &c., in any length, without any care on the part of the operator, to the enormous extent, if necessary, of 7000 feet per hour. The wire which he exhibited, as several in

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CHANGE IN THE CHEMICAL CHARACTER OF MINErals.

the Section knew, was not more perfectly manufactured than the many thousand feet he had covered lately. He thought the shock and spark might arise in this way: a current of electricity passes through the wire from copper to zinc; its inductive action on the wire ceases suddenly, by the contact with the bat tery being interrupted; the disturbed equilibrium of the wire is suddenly restored. The electricity of the battery seems, in passing through the helix, to acquire an aug. mented intensity; but from these facts it is evidently not so. 4thly. The spark and shock appear to demonstrate that currents do not circulate around the magnet. If they dó, as is evident, they are capable, as we know from secondary currents, of producing a spark and shock. The helix, of itself, is capable of these effects: let the helix and the magnet act conjointly; these effects ought to be doubled; the contrary is the fact; they may be annihilated, and they ought, for the magnet, by its electrical action, retains the helix in a state of excitation. The universal

at least in other cases-law of electrical induction, if applied to magnetic phenomena, easily explains them. He did not think it by any means certain, that electrical action consists in the transmission of a fluid, and not the mere arrangement of particles: this idea seemed opposed by an experiment he made some time ago. He never could believe that the action of the galvanic battery consisted in the passage of electricity through the fluid from zinc to copper, and along the connecting wire from copper to zine; he thought that the repulsion which sent the électricity through the fluid-an imperfect conductor-ought to prevent its return along the wire. He constructed a small box of wood, being a cube internally of three inches, divided it into twelve waterproof cells by well-cemented glass plates; placed in the cells six copper and six zinc plates, one in each, in the usual galvanic order; filled the cells with a charge of 1 in 50 sulphuric acid, 1 in 100 nitric acid and water, and connected the extreme plates with a delicate galvanometer, but no effect was produced, except when the copper and zinc were in the same cell, or the cells were in conducting communication; but he did not deem this experiment conclusive against his idea, since, although induction might occur from particle to particle, through an imperfectly conducting fluid, it by no means follows this inductive influence should take place through the particles of glass, since the very insulating power of glass, or other substances, may arise from the incapacity of their particles for electrical arrangement.

If it be true, that electrical effect is the arrangement, and not the transmission, of

particles, he thought we might easily understand the agitation of the muscles of a frog, caused in breaking contact with a galvanic battery, even of a single circle; the dangerous effects to those in the neighbourhood of the discharge of lightning from cloud to cloud; and the spark and shock obtained from a quantity of wire-all of which probably arise from the same cause, and are the consequence of the same universal law.

Professor Ritchie rose to remark, that without intending to convey the least censure on the gentleman, he could not but observe, that he had been so entirely occupied with his own researches as not to have attended to any thing done by others, for there was really nothing new in this paper-and he gave examples.

Professor Stevelly remarked, that if the only objection to it were the crank and mag. netic pendulum not working together, in a large machine that could be at once remedied, by what was well known in practical mechanics, a slipping coupling, as, when the steam-engine and water-wheels were made to work together, was generally done, or as in the winding part of the common clock. The great objection was the small distance through which the power worked, one-sixteenth of an inch; thus, even if a magnet could be produced that would lift 1,000 lbs., would still

render the numerical value of the horsepower almost evanescent compared with the steam engine.

ON THE CHANGE IN THE CHEMICAL CHARACTER OF MINERALS INDUCED BY GALVANISM, AND ON THE ARTIFICIAL PRODUCTION OF CRYSTALS AND MINERALS. (From the Times Report of the Fifth Day's Próceelings of the A-sociation, Friday, Aug. 26.)

Mr. Fox mentioned the fact, long known to miners, of metalliferous veins intersecting different rocks containing ore in some of these rocks, and being nearly barren, or entirely so, in others. This circumstance suggested the idea of some definite cause; and his experiments on the electrical magnetic condition of metalliferous veins, and also on the electric conditions of various ores to each other, seem to have supplied an answer, inasmuch as it was thus proved that electromagnetism was in a state of great activity under the earth's surface, and that it was independent of mere local action between the plates of copper and the ore with which they were in contact, by the occasional substitution of plates of zinc for those of copper, producing no change in the direction of the voltaic currents. He also referred to other experiments, in which two different varieties

ARTIFICIAL CRYSTALS AND MINERALS.

of copper ore, with water taken from the same mine, as the only exciting fluid, produced considerable voltaic action. The various kinds of saline matter which he had detected in water taken from different mines, and also taken from parts of the same mine, seemed to indicate another probable source of electricity; for can it now be doubted, that rocks impregnated with or holding in their minute fissures different kinds of mineral waters, must be in different electrical conditions or relations to each other? A general conclusion is, that in these fissures metalliferous deposits will be determined according to their relative electrical conditions; and that the direction of those deposits must have been influenced by the direction of the magnetic meridian. Thus we find the metallic deposits in most parts of the world having a general tendency to an E. and W., or N. E. and S. W. bearing. Mr. Fox added, that it was a curious fact, that on submitting the muriate of tin in solution to voltaic ac tion to the negative pole of the battery, and another to the positive, a portion of the tin was determined like the copper, the former in a metallic state, and the latter in that of an oxide, showing a remarkable analogy to the relative position of tin and copper ore with respect to each other, as they are found in the mineral veins.

The Chairman said, it had been observed to them last evening, that the test of some of the highest truths which philosophy had brought to light was their simplicity. He held in his hand a blacking-pot, which Mr. Fox had bought yesterday for a penny, a little water, clay, zinc, and copper, and by these humble means he had imitated one of the most secret and wonderful processes of Nature-her mode of making metallic veins. It was with peculiar satisfaction he contemplated the valuable results of this meeting of the Association. There was also a gentleman now at his right hand, whose name he had never heard till yesterday, a man unconnected with any Society, but possessing the true spirit of a philosopher; this gentleman had made no less than 24 minerals, and even crystalline quartz. (Loud cries of "Hear.") He (Dr. Buckland) knew not how he bad made them, but he pronounced them to be discoveries of the highest order; they were not made with a blacking-pot and clay, like Mr. Fox's, but the apparatus was equally humble; a bucket of water and a brickbat had sufficed to produce the wonderful effects which he would detail to them.

ARTIFICIAL CRYSTALS AND MINERALS. Mr. Cross, of Broomfield, Somerset, then eame forward, and stated that he came to Bristol to be a listener only, and with no idea

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he should be called upon to address a Section. He was no geologist, and but a little of a mineralogist; he had, however, devoted much of his time to electricity, and he had latterly been occupied in improvements in the voltaic power, by which he had succeeded in keeping it in full force for twelve months by water alone, rejecting acids entirely. (Cheers.) Mr. Cross then proceeded to state, that he had obtained water from a finely crystallised cave at Holway; and by the action of the voltaic battery had succeeded in producing from that water, in the course of ten days, numerous rhomboidal crystals, resembling those of the cave; in order to ascertain if light had any iufluence in the process, he tried it again in a dark cellar, and produced similar crystals in six days, with one-fourth of the voltaic power. He had repeated the experiments a hundred times, and always with the same results. He was fully convinced that it was possible to make even diamonds, and that at no distant period every kind of mineral would be formed by the ingenuity of man. By a variation of his experiments he had obtained grey and blue carbonate of copper, phosphate of soda, and 20 or 30 other specimens. If any members of the Association would favour him with a visit at his house, they would be received with hospitality, though in a wild and savage region on the Quantock Hills, and he should be proud to repeat his experiments in their presence. Mr. Cross sat down amidst longcontinued cheering.

Professor Sedgwick said he had discovered in Mr. Cross a friend, who some years ago kindly conducted him over the Quantock Hills on the way to Taunton. The residence of that gentleman was not, as he had described it, in a wild and savage region, but seated amidst the sublime and beautiful in nature. At that time he was engaged in carrying on the most gigantic experiments, attaching voltaic lines to the trees of the forest, and conducting through them streams of lightning as large as the mast of a 74-gun ship, and even turning them through his house with the dexterity of an able charioteer. Sincerely did he congratulate the Section on what they had heard and witnessed that morning. The operations of electrical phenomena, instances of which had been detailed to them, proved that the whole world, even darkness itself, was steeped in everlasting light, the first-born of heaven. However, Mr. Cross might have hitherto concealed himself, from this time forth he must stand before the world as public property.

Professor Phillips said, the wonderful discoveries of Mr. Cross and Mr. Fox would open a field of science in which ages might be employed in exploring and imitating the phenomena of nature.

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