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."

66

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. "Attractions of elect. bodies more accurate," p. 1-4.

166.]

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.

No. 10. MS. p. 52-132. Part *

No. 11.

295-385.

MS.

MS. p. 1-8. IA.

of Experiments. See Arts.

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. 438465, 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

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. 616631. "Res." Results of ditto p. 1-4. See Arts. 684-696. Resistance of Copper wire, p. 1-38.

No. 20. Experiments with the artificial

See Arts. 636–646. Torpedo, p. 1-26. See

Arts. 576-615. M. 1 to M. 42. Measurement of Leyden

* So in MS.

jars and batteries and of thickness of plates. See Arts. 581-592. "Extract from Dr Williamson's exper. on elect. Eel made in july 1773" p. 1 to 14+ 4 pp. (See Phil. Trans., 1775, p. 94.)

In Art. 349, p. 172 of this book, Cavendish uses the expression "when I wrote the second part of this work." It appears from this that he meant it for a book, not a paper to be communicated to the Royal Society. Several portions of this book are contained in the manuscripts, but the order in which they were intended to be placed can be discovered only by help of the figures and diagrams, which are numbered from 1 to 31.

From these it appears that we must begin with No. 4 and No. 5, the Preliminary Propositions and the Appendix. The Preliminary Propositions refer to the printed paper of 1771. The last proposition in that paper is numbered XXVII., and the first in the MS. is XXIX., so that one proposition appears to be missing, but as there are several drafts, in all of which the first proposition is numbered XXIX., it is probable either that Prop. XXVIII. is not lost, but must be sought for among the enunciations in the second. part of the printed paper, or else that Cavendish made a mistake in numbering his propositions.

The Lemmas, however, are numbered consecutively, the last in the printed paper being Lemma XI. and the first in the MS. Lemma XII.

The other mathematical manuscripts are either drafts of these propositions or jottings of calculations not intended for publication.

The paper entitled "Thoughts concerning electricity"§ (No. 18) is placed next. It forms a suitable introduction to the account of the experiments, as it indicates the leading ideas of Cavendish's researches. The paper has no date, but its contents show that it is an earlier form of the theory of electricity, which Cavendish had already abandoned before he wrote the paper of 1771. The pro

* This seems to refer to the second part of the paper in the Phil. Trans., 1771, p. 670, or Art. 132 of this edition, and shows that this paper was intended to form the first part of the "Work."

+ Arts. 140 to 174.

Arts. 175 to 194.

§ Arts. 195 to 216.

positions in No. 17 belong to this form of the theory, and are given

in Note 18.

We have next the account of the experiments, the order of

The style in which these papers are written leaves no doubt that they were intended to form a book, and to be published. They are given here without any alteration except in the case of a few abbreviations the meaning of which is either obvious or is explained in some other part of the MS. I have also divided them into articles for the sake of more convenient reference. All additions to the MS. are enclosed in square brackets.

After this I have placed the paper on the Torpedo from the Philosophical Transactions for 1776. This, I think, is the whole of the "work" which is extant, but it is by no means a complete account of Cavendish's electrical researches. There are three forms in which Cavendish recorded the results of his experiments:

1st. A Journal containing notes of every observation as it was made, with the particulars of the experiments, and measurements of the apparatus.

2nd. "Results," containing a comparison of the different measures of quantities as recorded in the Journal, and a deduction of the most probable result. See Arts. 647-696.

3rd. An account of the experiments written for publication.

I have reproduced the journals for 1771* and 1772† entire, because they form a good example of Cavendish's method of work, and because they contain all the data of some of the most important electrical measurements.

The journal for 1773‡ is much larger than the others, and gives an account of many interesting and important researches.

Many pages of this journal, however, are filled with the details of the experiments for the comparison of the coated plates which

Arts. 438 to 465.

+ Arts. 466 to 493.

Arts. 494 to 580.

Cavendish used as standards of capacity. These experiments differ in no respect from those in the former journals, and all the conclusions which Cavendish deduced from them are stated by himself in the "Results." I have therefore thought it best to omit them from the journal, but to retain Cavendish's heading of each experiment and its date when known, and to make the numbers of the omitted articles run on continuously with those retained.

Many of the entries in the journals give the day of the week and of the month, but very few of them give the year. I have therefore ascertained in what years the stated days of the week and month coincided, and have inserted the most probable year within square brackets. It thus appears that the journal entitled "Experiments in 1773" begins with experiments made in October, 1772. Cavendish appears, however, to have got wrong in his reckoning for a good many days together during that month. See Art. 502.

It is somewhat difficult to account for the fact, that though Cavendish had prepared a complete description of his experiments on the charges of bodies, and had even taken the trouble to write out a fair copy, and though all this seems to have been done before 1774, and he continued to make experiments in electricity till 1781, and lived on till 1810, he kept his manuscript by him and never published it. It was not till 1784 that he communicated to the Royal Society those "Experiments on Air," including the production of water and of nitric acid, the absorbing interest of which might perhaps account for some neglect of his electrical writings.

Cavendish cared more for investigation than for publication. He would undertake the most laborious researches in order to clear up a difficulty which no one but himself could appreciate, or was even aware of, and we cannot doubt that the result of his enquiries, when successful, gave him a certain degree of satisfaction. But it did not excite in him that desire to communicate the discovery to others which, in the case of ordinary men of science, generally ensures the publication of their results. How completely these researches of Cavendish remained unknown to other men of science is shown by the external history of electricity.