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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 actiun, 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 arting 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 si:nultaneous 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 bappen 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. IC

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 wo if the magnet which holds it be not ready at once to send it offa thing very probable—the fly-wheel con. tinues 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 attachinent 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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373 becoming in him to suggest any thing to the at a negative conclusion--that if the agent British Association ; but he believed nothing under consideration be electricity, it differs would be more conducive to the interests of from the ordinary electricity in quantity, inscience, than that the Association should tensity, or both. For though we never had cause to be instituted a series of experiments been able with galvanism to cause the leaves on the galvanic battery and its charge, which of the electrometer to diverge, or with mawould set all questions on the mater at rest chine electricity to deflect the galvanometer, for ever. Before he left this part of the or with electricity to produce magnetism, or subject, he thought it well to recall the at. with magnetism, electricity, with electricity tention of the Section to the nature of the to produce heat, with heat, electricity,-their power obtained by electro-magnetism. In non-identity would by no means follow. To steam, one great cause of the varying power examine with ease and certainty the identity of the engine arises from the varying leverage of any thing with electricity, we must find of the crank. Let B and B’ be positions of some property of electricity, which is not the extremity of the piston-rod, C'R and modified by, nor dependent on, quantity or C'R' corresponding positions of the crank, intensity. We know, and chemistry furthe leverage of the crank is measured by the nishes us with one proof, that the elements of perpendicular CP and C'P'. It varies as things may be the same as to quantity, and that perpendicular.

But in electro-magnet- as to the intensity of mutual action; and yet ism, the force at B, say the bar traversing may be productive of vastly different effects. between the magnets, is always varying. He Thus we know, that from two equal volumes would not then enter into some curious results of carbon and hydrogen, may be formed at obtained by calculation on this matter. least three very different substances.

The following facts seem to afford addic

tional evidence of the perfect identity of electricity and magnetism; and that magnetism does not require, nor suppose, the circulation of electrical currents.

Ist. 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 В

effects of the battery; for to obtain a shock

-(this shock he had not seen remarked by B


any experimentalist)—it is not necessary to

form a part of the communication beiween He had been anxious to satisfy himself, by the copper and zinc, but merely belween the his own experiment, of the truth of the law extremities of the helix, or between either of magnetic attraction being in the propor- extremity of the helix and the copper or zinc tion of the inverse square of the distance, of the battery. 3rdly. The shock and spark but abandoned the inquiry for the present, do not arise from the magnetism of the bar when he found that a magnet, with a seem- included in the helix, since the more perfectly ingly appropriate bar, would list at one- the bar is de-magnetised in breaking contact sixteenth of an inch only five pounds; though the better. Besides, it is curious that a with a different bar it litted the same weight powerful shock and brilliant spark may be at twelve times the distance; and that the obtained without any iron, and from a heap greater the distance through which powerful of wire thrown without any heliacal arrangeattraction might be exerted, the less the ment. This, Mr. M'Gauley remarked, would lifting power appeared.

lead to a very simple and effective electrical In examining the identity of electricities apparatus, one easily managed, and always derived from different sources, it seemed to ready for use; the length and number of the Mr. M'Gauley that we sometimes forget that coils, with a given calorimeter, has an effect electricity may be modified both as to quan- on the shock and spark. Mr. M'Gauley extity and intensity; and that if either be hibited to the Section wire coiled with the changed, or both, we cannot expect the same

greatest accuracy, by a machine he had results. To test, therefore, the identity of constructed, which was capable of covering any agent with electricity, we must not use any wire, manufacturing pianoforte strings, those means which are the measure of, or &c., in any length, without any care on the dependent on, either quantity or intensity; part of the operator, to the enormous exfor if in such experiments the electrometer or tent, if necessary, of 7000 feet per hour. galvanometer be not affected, we only arrive The wire which he exhibited, as several in



374 CHANGE IN THE CHEMICAL CHARACTER OF MINERALS. the Section knew, was not more perfectly particles, he thought we might easily undermanufactured than the many thousand feet stand the agitation of the muscles of a frog. he had covered lately. He thought the slock caused in breaking contact with a galvanic and spark might arise in this way: a current bartery, eren of a single circle; the danger. of electricity passes through the wire from ous effects to those in the neighbourhood of copper to zinc; its inductive action on the the discharge of lightning from cloud to wire ceases suddenly, by the contact with the cloud; and the spark and shock obtained bat tèry being interrupted; the disturbed from a quantity of wire-all of which proequilibrium of the wire is suddenly restored. bably arise from the same cause, and are the The electricity of the battery seems, in pass- consequence of the same universal law. ing through the helix, to acquire an aug.

Professor Ritchie rose to remark, that with. mented intensity; but from these facts it is

out intending to convey the least censure on évidently not so. 4thly. The spark and

the gentleman, he could not but observe, shock appear to demonstrate that currents do

that he had been so entirely occupied with his not circulate around the magnet. If they

own researches as not to have attended to any do, as is evident, they are capable, as we

thing done by others, for there was really know from secondary currents, of producing

nothing new in this paper--and he gave ex. å spark and shock. The helix, of itself, is

amples. capable of these effects : let the helix and the magnet act conjointly; these effects ought to

Professor Stevelly remarked, that if the be doubled ; the contrary is the fact; they

only objection to it were the crank and maga máy be annihilated, and they ought, for the

netic pendulum not working together, in a magnet, by its electrical action, retains the

large machine that could be at once remedied; helix in a state of excitation. The universal

by what was well known in practical meat least in other cases-law of electrical

chanics, a slipping coupling, as, when the induction, if applied to magnetic phenomena,

steam-engine and water-wheels were made to easily explains them. He did not think it

work together, was generally done, or as in by any means certain, that electrical action the winding part of the common clock. The consists in the transmission of a fluid, and

great objection was the small distance through not the mère arrangement of particles: this

which the power worked, one-sixteenth of an idea seemed opposed by an experiment he

inch ; thus, even if a magnei could be promade some time ago. He never could believe

duced that would lift 1,000 lbs., would still that the action of the galvanic battery con

render the numerical value of the horse. sisted in the passage of electricity through

power almost evanescent compared with the the Auid from zinc to copper, and along the

steam.engine. connecting wire from copper to zinc; he thought that the repulsion which sent the

ON THE CHANGE IN THE CHEMICAL CHA. electricity through the fuid-an imperfect


MINERALS INDUCED conductor-ought to prevent its return along

GALVANISM, AND ON THE ARTIFICIAL PROthe wire. He constructed a small box of

DUCTION OF CRYSTALS AND MINERALS, wood, being a cube internally of three inches, divided it into twelve waterproof cells by

(From the Times Report of the Fiftli Day's Pro

ceedings of the Association, Friday, Aug. 26.) well-cemented glass plates ; placed in the cells six copper and six zinc plates, one in each, Mr. Fox mentioned the fact, long known in the usual galvanic order; filled the cells to miners, of metalliferous veins intersecting with a charge of 1 in 50 sulphuric acid, lin different rocks containing ore in some of 100 nitric acid and water, and connected these rocks, and being nearly barren, or enthe extieme plates with a delicate galvano. tirely so, in others. This circumstance sug. metër, but no effect was produced, except gested the idea of some definite cause; and when the copper and zinc were in the same his experiments on the electrical mágñetic cell, or the cells were in conducting commu- condition of metalliferous veins, and also on nication ; but he did not deem this experi- the electric conditions of various orës to each ment conclusive against his idea, since, al- other, seem to have supplied an answer, in. though induction might occur from particle asmuch as it was thus proved that electroto particle, through an imperfectly conduct- magnetism was in a state of great activity ing fuid, it by no means follows this inductive under the earth's surface, and that it was influence should take place through the par. independent of mere local action between the ticles of glass, since the very insulating power places of copper and the ore with which they of glass, or other substances, may arise from were in con act, by the occasional substitu. the incapacity of their particles for electrical tion of plates of zinc for those of copper, arrangement.

producing no change in the direction of the If it be true, that electrical effect is the voltaic currents. He also referred to other arrangement, and not thie transmission, of experiments, in which two different varieties




375 of copper ore, with water taken from the he should be called upon to address a Section. same mine, as the only exciting fluid, pro- He was no geologist, and but a little of a duced considerable voltaic action. The va- mineralogist; he had, however, devoted much rious kinds of saline matter which he had of his time to electricity, and he had latterly detected in water taken from different mines, been occupied in improvements in the voltaic and also taken from parts of the same mine, power, by which he had succeeded in keeping seemed to indicate another probable source of it in full force for twelve months by water electricity; for can it now be doubted, that alone, rejecting acids entirely. (Cheers.) Mr. rocks impregnated with or holding in their Cross then proceeded to state, that he had minute fissures different kinds of mineral obtained water from a finely crystallised cave waters, must be in different electrical con- at Holway; and by the action of the voltaic ditions or relations to each other? A ge- battery had succeeded in producing from that neral conclusion is, that in these fissures water, in the course of ten days, numerous metalliferous deposits will be determined ac- rhomboidal crystals, resembling those of the cording to their relative electrical conditions; cave ; in order to ascertain if light had any and that the direction of those deposits must iufluence in the process, he tried it again in a have been influenced by the direction of the dark cellar, and produced similar crystals in magnetic meridian. Thus we find the me. six days, with one-fourth of the voltaic power. tallic deposits in most parts of the world He had repeated the experiments a hundred having a general tendency to an E. and W., times, and always with the same results. He or N. E. and S. W. bearing. Mr. Fox added, was fully convinced that it was possible to that it was a curious fact, that on submitting make even diamonds, and that at no distant the muriate of tin in solution to voltaic ac- period every kind of mineral would be formed tion to the negative pole of the battery, and by the ingenuity of man. By a variation of another to the positive, a portion of the tin his experiments he had obtained grey and was determined like the copper, the former in blue carbonate of copper, phosphate of soda, & metallic state, and the latter in that of an and 20 or 30 other specimens. If any memoxide, showing a remarkable analogy to the bers of the Association would favour him with relative position of tin and copper ore with a visit at his house, they would be received respect to each other, as they are found in with hospitality, though in a wild and savage the mineral veins.

region on the Quantock Hills, and he should

be proud to repeat his experiments in their The Chairman said, it had been observed

presence. Mr. Cross sat down amidst longto them last evening, that the test of some ued cheering. of the highest truths which philosophy had

Professor Sedgwick said he had discovered brought to light was their simplicity. He in Mr. Cross a friend, who some years ago held in his hand a blacking-pot, which Mr. kindly conducted hiin over the Quantock Hills Fox had bought yesterday for a penny, a on the way to Taunton. The residence of that little water, clay, zinc, and copper, and by

gentleman was not, as he had described it, these humble means he had imitated one of

in a wild and savage region, but seated the most secret and wonderful processes of amidst the sublime and beautiful in nature. Nature-her mode of making metallic veins. At that time he was engaged in carrying on It was with peculiar satisfaction he contem

the most gigantic experiments, attaching vol. plated the valuable results of this meeting of tais lines to the trees of the forest, and conthe Association. There was also a gentleman

ducting through them streams of lightning as now at his right hand, whose name he had

large as the mast of a 74-gun ship, and even never heard till yesterday, a man unconnected

turning them through his house with the with any Society, but possessing the true

dexterity of an able chariotter. Sincerely spirit of a philosopher; this gentleman had

did he congratulate the Section on what they made no less than 24 minerals, and even

had heard and witnessed that morning. The crystalline quartz. (Loud cries of “Hear.")

operations of electrical phenomena, instances He (Dr. Buckland) knew not how he bad

of which had been detailed to them, proved made them, but he pronounced them to be

that the whole world, even darkness itself, discoveries of the highest order; they were was steeped in everlasting light, the first-born not made with a blacking-pot and clay, like of heaven. However, Mr. Cross might have Mr. Fox's, but the apparatus was equally hitherto concealed himself, from this time humble; a bucket of water and a brickbat

forth he must stand before the world as pube had sufficed to produce the wonderful effects

lic property. which he would detail to them.

Professor Phillips said, the wonderful dis

coveries of Mr. Cross and Mr. Fox would ARTIFICIAL CRYSTALS AND MINERALS.

open a field of science in which ages might Mr. Cross, of Broomfield, Somerset, then be employed in exploring and imitating the eame forward, and stated that he came to phenomena of nature. Bristol to be a listener only, and with no idea

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