Benjamin Franklin Papers

To Benjamin Franklin from Joseph Priestley, 21 September 1766

From Joseph Priestley

ALS: American Philosophical Society

Warrington 21 Sepbr. 1766.

Dear Sir

I wrote to Mr. Price last post, in which I desired him to remind you of your promise to procure me Beccaria’s work, which you said you thought you could do of Mr. Delaval.5 Fearing he might not see you soon, I write to desire you to get it for me, if possible, without loss of time. Otherwise, I must reserve his experiments for an Appendix, for, by the references I meet with to them, I find my book absolutely must not come abroad without them. I am in such haste, as we have already begun to print, and have done five sheets. The whole work will make betwixt 400, and 500 pages 4to, and we shall not have done quite so soon as Christmas.6 For the same reason, I must beg you would also send me, as soon as you conveniently can, the two last numbers of the work, which I left in the hands of Dr. Watson, to be transmitted to you.7 I am now wholly employed in revising and correcting. I defer drawing up the account of my own experiments, till I have some more in pur[s]uance of them, and several others.8 In about a week I shall betake myself to experiments in good earnest, but I have no expectation of doing much more than I have done. Upon Mr. Price’s letter, I sent the mark that was actually made by a chain when a discharge was sent thro it.9 I have several times since I came home got three, and almost always two concentric circles, upon the metal knobs with which I make discharges.1 If I verify your experiments on the electrified cup, and animal fluids, may I publish them as yours, in some proper place in my work?2 I shall soon go about them. Have you procured the list of books written on the subject of electricity, or the remainder of Wilke’s treatise.3 Dr. Watson has sent me a curious tract of Johannes Franciscus Cignas which I am now digesting.4 In your notes [on] one of my former Numbers you say, you question whether Æolipyle5 will turn the same way whether it draw in [or] throw out the water. I had tried it before I wrote [the] paragraph, you may depend upon the fact. I hope to find more of your excellent remarks upon the two numbers in your hands. I am, Dear Sir, your most obliged humble servant

J Priestley

Since I wrote the letter, I have made a discharge, through a chain that lay on this side of it.6 At the moment of the discharge, the whole appeared like a bright flame. From (a) when the chain was returned, it was thrown back as far as (b).7 I have tried the same several times since, laying one half of a chain parallel to the other, and marking exactly how far it reached upon the table; and always found the middle part pulled back about an inch and a half [as] if a sudden jerk had been given [to] it. Indeed it was manifest, by comparing the links with the marks, that every link had moved a little. Must not that have been effected by the links repelling one another, while the shock was passing? Is not the paper really burnt? Was not the chain made superficially hot? and does not the electric shock pass chiefly over the surfaces of bodies? so that small bodies will be melted, because they have most surface in proportion to their bulks. nb The fa[int] marks, at a distance from the rest, are not made [by] handling. They are just as the discharge left them. Indeed, you will find they are not easily effaced. nb The wire of the chain is not so thick as the marks.8

Addressed: To / Doctor Franklin / at Mrs Stephens / in Craven Street in the Strand / London

[Note numbering follows the Franklin Papers source.]

5Richard Price, William Watson, John Canton, and BF were giving help and criticism to Priestley in the preparation of his History of Electricity. It is not certain which of Beccaria’s works Priestley wanted at this time: either Dell’ elettricismo: artificiale e naturale (Turin, 1753) or Dell’ elettricismo: lettere (Bologna, 1758); see above, V, 395–6, 428; VII, 315. The former was probably the one desired, though Priestley cited both often in his book. On Edward Hussey Delaval of Pembroke College, Cambridge, from whom BF was to procure the book, see above, VIII, 360–1 n.

6The main text of the book, not including front matter, “Additions and Corrections,” or index, runs to 733 pages quarto. The book was advertised as just published in London Chron., March 31–April 2, 1767.

7Priestley probably meant the last two installments of the text as he had written it and left it in Watson’s hands for criticism.

8In Part viii (pp. 573–733) Priestley presented “an account of such new experiments in electricity as this undertaking has led me to make.” His reports are written in the first person, and many are given specific dates.

9On this matter see Priestley’s postscript to this letter and its accompanying notes and illustration.

1Priestley described this and related phenomena in his History, pp. 660–71, with the dates of June 13–28, 1766, assigned to his experiments.

2Priestley described experiments with an electrified cup, Dec. 21, 1766, acknowledging that he had “little to boast besides the honour of following the instructions of Dr. Franklin.” Ibid., pp. 731–3. He had reported on p. 212, Beccaria’s experience with the bursting of the blood vessels of small birds killed by electric shocks, and added that BF found animal fluids to conduct better than water. In his “Additions and Corrections,” p. 835, Priestley admitted that the reference to BF had been added from memory as “more accurate information” had reached him too late. But BF had told him that Ebenezer Kinnersley and others in America had found blood and urine and the sinews of newly killed animals to be better conductors than water.

3BF may have promised to try to look up and send a copy of the list of books on electricity Pieter van Musschenbroek had sent him in 1759; above, VIII, 329–33. Johan Carl Wilcke (1732–1796) published his Disputatio physica experimentalis de electricitatibus contrariis (Rostock, 1757) in four parts, but Priestley admitted in his bibliography that the copy he had used contained only the first three parts. “It was that [copy],” he explained, “which the author sent to Dr. Franklin, before the remainder was printed.”

4Gian Francesco Cigna (1734–1791), a nephew of Beccaria, later professor of Anatomy at Turin, published a piece, De novis quibuidam experimentis electricis, in the Memoirs of the Academy of Turin for 1765; see below p. 453.

5An Aeolipile or aeolipyle is described as an apparatus in which a globe or cylinder may be made to revolve by the discharge of jets of steam from projecting bent tubes. It has been called the first steam engine. The word is sometimes also used for a blowpipe. The editors confess their inability to understand Priestley’s use of the word here or to find any reference to such an apparatus in his History.

6All of this postscript appears on the third page of the folio, which is somewhat torn at the right edge and where the seal on the address page (the other side of this leaf) had been ripped away. This explanatory postscript fills the whole page except for the space occupied by the marks of the chain Priestley used in the experiment; these are shown in the accompanying illustration.

7That is, the apex of the “V” retracted from “a” to “b.”

8In his History Priestley described experiments he performed in September 1766 with a brass chain through which he sent an electrical discharge while it lay on a piece of white paper. He found that it made black marks on the paper, and lost a little weight. He then continued his account under date of September 21 (the date of this letter) as follows: “In making the mark above-mentioned, on part of the sheet of paper, on which I had written an account of the experiment to Dr. Franklin, I happened to lay the chain so as to make it return at a sharp angle [at the point marked “a” in the illustration], in order to impress the form of a letter on the paper; and observed that, upon the discharge, the part of the chain that had been doubled was displaced, and pulled about two inches towards the rest of the chain [to the point marked “b” on the illustration]. At this I was surprised, as I thought it lay so, as that it could not slide by its own weight. Upon this I repeated the experiment with more accuracy. I stretched the whole chain along a table, laying it double all the way, and making it return by a very sharp angle. The consequence always was, that the chain was shortened about two inches, and sometimes more; as if a sudden pull had been given to it by both the ends.” History of Electricity, pp. 672–5 (quotation is on pp. 674–5, and is followed, pp. 675–84, with further experiments and discussion of the phenomena observed).

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