Benjamin Franklin Papers

To Benjamin Franklin from Joseph Priestley, 13 April 1766

From Joseph Priestley

ALS: American Philosophical Society

Warrington. 13 Ap. 1766

Dear Sir

I this day received your favour of the 10th instant, and the day before yesterday another letter, with several parcels of books, containing all that are mentioned in your letters.9 At the same time I received a parcel from Dr. Watson, containing, among others, the same history of electricity which you have sent me.1 I shall immediately apply myself to the purusal of them all, with the greatest attention, and I make no doubt but from these, and other books which I hope you will be able to procure me, I shall make many valuable additions to my history. I need not tell you, that you will find it, in the condition in which it comes into your hands, very imperfect. It contains indeed every[thing] that the materials I then had by me [could furnish?], but [some?] very important articles have already [fallen] my way [torn]. When Mr. Canton sends me his Gilbert, [I shall] not fail to enrich my work with a particular account [of] all that he did in electricity. If I cannot get Otto Gueric, I must copy what is said of him in the history you have sent me.

I shall be very glad to hear your remarks on my experiment with the vanes, tho’ I am quite satisfied, that it is perfectly agreeable to your general theory. You will find some additional experiments with the vanes in my letter to Mr. Canton.

Since I sent my last two numbers to Mr. Price, I have neither written a line on the subject of electricity, nor made any experiments of consequence, having been wholly employed in constructing an electrical machine upon a new, and, I think, in many respects, an improved plan. I propose to give a particular description and a cut of it in the book.2

I have not repeated my experiments with condensed air since I wrote to Dr. Watson, but in a piece of Boulanger3 which he has sent me I find that the same experiment had been made before, and with the same success. This author adds, that the impossibility of exciting a tube in which air is condensed cannot be owing to moisture, as some suspect; for if a drinking glass full of water be poured into the tube, and poured out again, it will not destroy its electrifying power so effectually as the condensed air. He adds, in another place, that Marcassites4 are incapable of being excited, chiefly on account of the condensed air that is in them. This last is certainly a very gro[u]ndless supposition. I think, with you and Dr. Watson, that the effect is, some way or other, owing to moisture. Mr. Boulanger did not know, that when the [air] was heated it might be excited, though it did contain [torn]. This is not the first or second time [in] which [I have found] myself anticipated in experiments which I imagi[ned h]ad been originally my own. The blast from electrified [poin]ts and even the blowing of the candle I find mentioned by Nollet.5 But he did not pursue the experiment, and he argues very weakly from it. I am ashamed when I think of the experiment with mephitic air, but I made use of every precaution I could think of, and others were deceived as well as myself.

I was yesterday favoured with a letter from Mr. Canton. Please to present my compliments to him. Tell him I thank him for the curious particulars it contains, and that I shall, with great pleasure, make the use of them that he desires, as well as strictly conform to every thing else that he requests of me. I sincerely ask his pardon for my hasty misapprehension of his observations on hot air, but I think he will find that I have not made that mistake in the history.6 When I have made some more experiments on hot air and on effluvia, I will write to him again.

I shall not forget the motto of your seal.7 I consider Mr. Wilson’s performance in the same light that you do.8

If electrics naturally contain more of the electric fluid than other bodies, should not red hot glass, as it cools, draw the fluid from the bodies with which it is in contact? I placed a piece of red hot glass and let it cool upon a very smooth piece of insulated copper, without perceiving any such effect.

I hope you will be able to procure me Beccaria.9 I am sorry that Wilke’s piece1 is not complete. I greatly admire. Æpinus.2 I hope you will make very free with the blank page of my mss. I shall be sorry if I find but little in it. I am much obliged to [torn] explanation of two latin terms. If [torn] take of that kind, I hope you will [torn] sometime inclused French words in brac[kets] doubtful of my rendering of them. I am, with the greatest gratitude and re[spect] Dear Sir Your most obliged humble servant

J Priestley

Addressed: To / Do[ctor Frankli]n / at Mrs Stephens’s in Craven street / in the Strand / London

[Note numbering follows the Franklin Papers source.]

9Neither of BF’s letters mentioned here has been found. Many of the persons, books, and experiments discussed in the present letter have received editorial comment in the notes to Priestley’s letter to BF of March 25, 1766; above, pp. 199–202. It should be read in conjunction with this letter. These letters and those of the same period to other electricians in London are conveniently printed as a group in Robert E. Schofield, ed., A Scientific Autobiography of Joseph Priestley (1733–1804), (Cambridge, Mass. and London, [1966]), pp. 12–49.

1Perhaps the “histoire de l’électricité,” by either Abbé de Mangin or Thomas-François Dalibard, which Priestley requested in his letter of March 25.

2Part v of Priestley’s History of Electricity is devoted to electrical machines. His own machine is described on pp. 530–4 with an accompanying plate.

3A work described in Priestley’s History, facing p. 736, as “Boulanger’s Traité de la cause et des phenomenes de l’electricité, 1750, Paris.” Priestley noted that he had “seen no more than one part of this treatise, which I had of Dr. Watson. How many more parts there are of the whole work, I have not been informed.”

4Marcasites: crystallized iron pyrites.

5Jean-Antoine Nollet, one of BF’s earliest and most notable scientific antagonists; see above, IV, 423–8. Priestley cited his “Conjettures sur les causes de l’electricité des corps, Paris, 1745” and his “Essai sur l’electricité des corps, 1746, 1754, Paris” in the bibliography to his History.

6For Canton’s experiments on the relationship between heat and the conductivity of electricity in which he differed with Edward Delaval, see above, X, 23–6, 74–5. Priestley summarized the Canton-Delaval controversy in his History, pp. 237–45.

7The Franklin arms, above, ii, facing 230, contained the motto: “Exemplum adest ipse homo”—the example presents the man himself.

8BF must have considered Benjamin Wilson’s electrical work incomprehensible, as Priestley confessed that he had in his letter of March 25; see above, p. 201.

9Giambatista Beccaria, professor of experimental physics at Turin, and one of BF’s defenders in his controversy with Nollet; see above, V, 395 n. In the bibliography to his History, facing p. 736, Priestley noted that BF had sent him a copy of Beccaria’s Dell’ elettricismo artificiale e naturale (Turin, 1753).

1Johanne Carolus [Johan Carl] Wilcke, Disputatio physica experimentatis de electricitatibus contrariis (Rostock, 1757).

2Franz Ulrich Theodor Aepinus, professor of physics at St. Petersburg; see above, VIII, 393–5; X, 204–5, 266–7.

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