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“He, who by Reason became an electrician, will hear with reverence “ of an instinctive electrician, gifted in his birth with a wonderful “ apparatus, and with the skill to use it*.

“However I may respect your talents as an electrician, it is certainly for knowledge of more general import that I am impressed “with that high esteem, with which I remain,

“Dear Sir,
“ Your affectionate
“ And obedient servant,

“JOHN WALSH."

This paper is followed in the Philosophical Transactions by “Anatomical Observations on the Torpedo," by John Hunter, F.R.S., in which the great anatomist describes the structure of the electric organs, in specimens of the fish furnished by Mr Walsh

Considerable interest seems to have been excited by this account of the Torpedo, and several papers on the Torpedo and the Gymnotus are in the Philosophical Transactions for 1775, none of them, however, so valuable as the original one by Walsh.

The practical electricians, however, were by no means satis

* That the electrical fishes still possess the power of exciting the imagination as well as the nerves of those who have felt their power may be seen from the following passage with which Prof. Du Bois Reymond begins his account of experiments on a living Malapterurus in the Monatsberichte d. k. Acad. Berlin, 28 Jan., 1858.

“Fast möchte man es, im Sinne Newton's, eine Anwandlung der Natur nennen, “ dass es ihr gefallen hat, aus der Unzahl der Geschöpfe drei Fische, und zwar

der verschiedensten Art, nach Willkür herauszugreifen, um sie mit elektromo. “torischen Vorrichtungen von furchtbarer Gewalt als eine Waffe auszustatten, “ neben welcher der Giftzahn der Klapperschlange, ja die nordamericanische Dreh"pistole, als eine plumpe und armselige Erfindung erscheint; eine Waffe die, ohne “ ihren Träger der Gefahr blosszustellen, lautlos und mit Blitzesschnelle in die “Entfernung reicht, und minutenlang eine secundendicht gedrängte Reihe von “Geschossen schleudert, deren keines fehlen kann, weil alle auf allen Punkten des “Raumes gleichzeitig vorhanden sind.”

In the Journal of Anatomy and Physiology for April, 1879, is a Note on a Curious Habit of the Malapterurus Electricus, by A. B. Stirling. The author attempted to feed Joe (the Malapterurus) with fresh worms, but he would not look at them. Another fish, however, called Dick (Clarias), swallowed them. When Joe considered that Dick had enjoyed his breakfast long enough, he swam up to him and gave him such a shock that the whole was disgorged, whereupon Joe swallowed it himself. When Dick at last succumbed to this treatment, Joe could no longer get his food prepared for him, and gave up eating altogether.

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fied that the effects of these fishes were really produced by electricity.

“Mr Ronayne has made a curious remark upon the supposed elec“tricity of the torpedo : he says, “if that could be proved, he does not

see why we might not have storms of thunder and lightning in the "depths of the ocean. Indeed, I must say, that when a Gentleman

can so far give up his reason as to believe the possibility of an " accumulation of electricity among conductors sufficient to produce ««the effects ascribed to the Torpedo, he need not hesitate a moment to embrace as truths the grossest contradictions that can be laid " • before him *!»

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I am aware of only two occasions on which Cavendish, after he had settled his own opinion on any subject, thought it worth his while to set other people right who differed from him. One of these occasions was in 1778, when his experiments on the formation of nitric acid by the electric spark from phlogisticated and dephlogisticated air (nitrogen and oxygen) had been repeated without success by Van Marum with the great Teylerian electrical machine, and by Lavoisier and Monge, and when Cavendish

thought it right to take some measures to authenticate the truth of it."

For this purpose he requested Mr Gilpin, clerk to the Royal Society, to repeat the experiment, and desired some of the gentlemen most conversant with these subjects to be present at putting the materials together, and at the examination of the producet.

The other occasion, with which alone we are now concerned, is the only one in which the presence of visitors to Cavendish's laboratory is recorded. There can be no doubt that Cavendish had completely satisfied not only Mr Walsh, but what was more to the purpose, himself, that the electric phenomena of the torpedo are such as might arise from the discharge of a large quantity of electricity at a very feeble degree of electrification. It must therefore have been to satisfy other persons on this point that he took the trouble to construct an artificial torpedo of wood covered with leather, a rude model of the figure given

* Extract from MS. letter of W. Henly, dated 21 May, 1775, in the Canton Papers in the Royal Society's Library. Communicated to the editor by H. B. Wheatley, Esq. + Phil. Trans. 1788.

by Walsh, with electric organs of pewter supplied with electricity from a battery of Leyden jars, by wires protected by glass tubes.

The accessories of this machine were equally unlike the kind of apparatus which Cavendish made when working for himself. The torpedo had a trough of salt water, the saltness of which was carefully adjusted, so as to be equal to that of the sea. It had also a basket to lie in, and a bed of sand to be buried in, and there were pieces of sole-leather, well soaked in salt water, which Cavendish placed between the torpedo and his hands, so that he might form some idea of what would happen if a traveller with wet shoes were to tread on a live torpedo half buried in wet sand.

It was on Saturday, 27th May, 1775, that Cavendish tried the effect of his Torpedo on a select company of men of science. We find in the Journal (Art. 601), the names of John Hunter, the great anatomist, Dr Joseph Priestley, chemist, electrician and expounder of human knowledge in general, Mr Thomas Ronayne, from Cork, the disbeliever in the electrical character of the torpedo, Mr Timothy Lane, apothecary and electrician, and Mr Edward Nairne, the eminent maker of philosophical instruments.

They got shocks from the torpedo to their complete satisfaction, and probably learnt a good deal about electricity, but it was neither to satisfy them nor to communicate to them his electrical discoveries, that Cavendish admitted them into his laboratory on this memorable occasion, but simply to obtain the testimony of these eminent men to the fact, that the shocks of the artificial torpedo agreed in a sufficient manner with Walsh's description of the effects of the live fish, to warrant the hypothesis that the shock of the real torpedo may also be an electrical phenomenon.

I have now related all that I have been able to ascertain of the external history of Cavendish, in so far as it bears on his electrical researches. We must in the next place consider the record of these researches—the two papers in the Philosophical Transactions, which are here reprinted, and the manuscripts now first published.

CAVENDISH'S WRITINGS ON ELECTRICITY.

In the Philosophical Transactions for 1771 there is a paper entitled “An attempt to explain some of the principal Phænomena of Electricity by Means of an Elastic Fluid: By the Honourable Henry Cavendish, F.R.S.” [Read Dec. 19, 1771, and Jan. 9, 1772, pp. 584—677.] This paper and that on the Torpedo (Phil. Trans. 1776) are the only publications of Cavendish relating to electricity.

Dr George Wilson, however, in his Life of Cavendish * says,

“Besides his two published papers on electricity, Cavendish has “ left behind him some twenty packets of manuscript essays, more or “ less complete, on Mathematical and Experimental Electricity. These papers are at present in the bands of Sir W. Snow Harris, who most

kindly sent me an abstract of them, with a commentary of great " value on their contents. It will I trust be made public.

“Sir W. states that Cavendish had really anticipated all those great “facts in common electricity which were subsequently made known to “the scientific world through the investigations and writings of the “ celebrated Coulomb and other philosophers, and had also obtained the

more immediate results of experiments of a refined kind instituted in our own day.”

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Sir William Thomson, to whom Sir William Snow Harris showed some of Cavendish's results, thus speaks of them in a note dated Plymouth, Monday, July 2, 1849.

“Sir William Snow Harris has been showing me Cavendish's un“published MSS., put in his hands by Lord Burlington, and his work

upon them; a most valuable mine of results. I find already that “the capacity of a disc (circular) was determined experimentally by

1 " Cavendish as of that of a sphere of same radius. Now we

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2 “have capacity of disc

” “It is much to be desired that those manuscripts of Cavendish “should be published complete; or, at all events, that their safe keeping “and accessibility should be secured to the worldt."

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Works of the Cavendish Society, Vol. 1. Life of Cavendish, by George Wilson, M.D., F.R.S.E., London, 1851, p. 469.

+ Reprint of Papers on Electrostatics and Magnetism, g 235, foot-note.

The Cavendish Society, for whom Dr Wilson prepared his Life of Cavendish, with an account of his chemical researches, did not consider that it came within their design to publish his electrical researches.

Sir W. Harris, in whose hands the manuscripts were placed by the Earl of Burlington, died in 1867. He makes several references to them in his work on Frictional Electricity, edited after his death by Charles Tomlinson, F.R.S., and published in 1867*, but he did not live to edit the manuscripts themselves. Under these circumstances it was thought desirable by Sir W. Thomson, Mr Tomlinson, and other men of science, that something should be done to render the researches of Cavendish accessible.

They accordingly represented the state of the case to the Duke of Devonshire, to whom the manuscripts belong, and in 1874 he placed them in my hands.

I could find no trace of Sir W. Harris' commentary referred to by Dr Wilson, except that Dr Wilson mentions having returned it to Sir W. Harris.

On the inside of the lid of the box which contained the manuscripts was pasted a paper in the handwriting of Sir W. Harris, of which the following is a copy.

“The several parcels of manuscript papers by the late Mr Cavendish, “which the Earl of Burlington did me the honor to place in my hands " with a view to an examination and report on their contents may be “ taken at 24 in number. Twenty of these contain sundry Philo“sophical papers on Mathematical and Experimental Electricity, and “ Four sundry other Papers relating to Meteorology.

“All these Papers are more or less confused as to systematic arrange“ment, and require some considerable attention in decyphering. They “ are in many instances rather notes of experiments and rough drafts “ intended as a basis for more perfect productions than finished Philo“sophical Papers.

“They are nevertheless extremely valuable and most interesting as "evidence of Mr Cavendish's great Philosophical †

and clearly “prove that he had anticipated nearly all those great facts in common

electricity which at a later period were made known to the scientific “world through the writings of Coulomb and the French philosophers.

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* P. 23 (straw electrometer), p. 45 (globe and hemispheres), p. 58 (specific inductive capacity), p. 121 (measures of electricity), p. 208 (law of force), p. 223 (induction at a great distance).

+ So in MS.

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