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 66 papers are at present in the hands 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." 66 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 of that of a sphere of same radius. Now we 1 "Cavendish as 1.57 "have capacity of disc = 2 -- a = a π 1.571 "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 world +." * 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, § 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. * 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. Papers on Electricity. "Of the 20 parcels of papers on electricity 18 belong to the years "1771, 1772 & 1773, and have never yet appeared in print; the "two remaining parcels are dated 1775 and 1776, and are evidently "connected with the author's celebrated paper on the Torpedo pub"lished in the Royal Society's Transactions for 1776. The papers "belonging to the years 1771, 1772 & 1773 consist of six papers on "Mathematical Electricity, nine experimental papers, one of Diagrams "and Figures, the remainder are of a miscellaneous character, and "contain some interesting Notes and Remarks and Thoughts on Electricity." On examining the 20 parcels of manuscripts I found their contents to be as follows: No. 1. MS. p. 1-10. Apparently an early form of the "Preliminary Propositions." No. 2. MS. p. 1–31. Draft of "Preliminary Propositions" as far as Prop. XXIII. No. 3. MS. L. 3 to L. 23. Contains the same propositions in a less complete form and not numbered, also two drafts of the propositions on coated plates, each 12 pp., and 38 loose pages of drafts of propositions, and jottings of algebraical calculations. No. 4. MS. p. 1-48. The fair copy of the "Preliminary Propositions." Props. XXIX. to XXXVI. Refers to figs. 1 to 10 of No. 15. See Arts. 140-174. No. 5. MS. p. 1-20. "Appendix." Refers to fig. 11. See Arts 175-194. No. 6. "Computations for explanation of experiments." MS. p. 1-15. Drafts of the propositions. 16 pages of computations. "B. 17." Charge of a sphere within a concentric sphere. [This is placed here as a note at p. 166.] "Attractions of elect. bodies more accurate," p. 1-4. No. 7. MS. D. 1 to D. 13. Fair copy of First and Second Experiments. Refers to Figs. 12, 13. See Arts. 217-235. Draft of do marked "DIA." No. 8. MS. p. 1-7. No. 9. MS. p. 1-51. 236-294. Refers to Fig. 31. See Arts. 386-394. Continuation of Experiments. See Arts. of Experiments. See Arts. No. 10. MS. p. 52-132. Part* 295-385. No. 11. MS. p. 1–8. IA. IA. p. 10 A. 8, 9. p. 29 A. p. 32 A. 1 and 2. p. 57-64. p. 85, 86. p. 91-96. p. 103-108. p. 119-126. p. 133-138. p. 141, 142. p. 156-166. All drafts of portions of the Account of Experiments. No. 12. "Experiments 1771," MS. p. 1-24. See Arts. 438— 465, also 14 loose sheets of calculations and measurements. No. 13. "Experiments 1772," MS. p. 1-29. See Arts. 466-493. M. 1 to M. 13. Measurements of glasses, &c. See Arts. 592-595. No. 14. Experiment 1773, MS. p. 1-135. See Arts. 494-580. Index to elect. exper. 1773 p. 1-8. See Contents. Dimensions of trial plates, 4 pages. No. 15. Figures and Diagrams. 1 to 10 refer to Preliminary propositions No. 4 Appendix No. 3 No. 7 No. 9 No. 16. "Result." MS. p. 1-21. See Arts. 647-683. No. 17. "Notes." 4 pp. notes to "Thoughts concerning Electricity." These are inserted in their proper places, Arts. 196-216. MS. p. 1 to 15. Drafts of propositions for the paper of 1771, but founded on the theory stated in the "Thoughts." They are given in Note 18, p. 411. No. 18. "Thoughts concerning Electricity," MS. p. 1-16. See Arts. 196-216. No. 19. Resistance to Electricity, MS. p. 1-23. See Arts. 616— 631. "Res." Results of ditto p. 1-4. See Arts. 684-696. Resistance of Copper wire, p. 1-38. See Arts. 636-646. Torpedo, p. 1-26. See No. 20. Experiments with the artificial Arts. 576-615. M. 1 to M. 42. Measurement of Leyden # So in MS. |