Benjamin Franklin Papers

From Benjamin Franklin to Joseph Priestley, 4 May 1772

To Joseph Priestley

ALS (draft): American Philosophical Society

London, May 4 1772

Dear Sir,

I think with you that there cannot be the least Occasion for my explaining your Method of impregnating Water with fix’d Air to Messrs. Banks and Solander, as they were present and I suppose are as well acquainted with it as my self; however I shall readily do it if they think it necessary. I am glad you intend to improve and publish the Process.1

You must go half an Inch farther with your Spark to exceed what I show’d here with my Philada Machine in 1758 to Lord Charles Cavendish and others, who judg’d them to be nine Inches. My Cushion was of Buckskin with a long damp Flap, and had a Wire from it thro’ the Window down to the Iron Rails in the Yard; the Conductor of Tin 4 feet long and about 4 Inches Diameter. So powerful a Machine had then never been seen in England before, as they were pleas’d to tell me. A Machine was made from mine for Mr. Symmer, and was afterwards in the Possession of Lord Morton. A more convenient Construction I have never since seen, except that of yours.2

I intend soon to repeat Barletti’s Experiments,3 being provided with the Requisites, and shall let you know the Result.

I should be glad to see the French Translation of your Book. Can you conveniently lend it to me when you have perus’d it? I fancy it was translated at the Request of Abbé Nollet by a Friend and Disciple of his as I know there was one (whose Name I have forgotten,) that us’d to translate for him Extracts of English Electrical Books.4 The Abbe’s Machine was a very bad one, requiring three Persons to make the smallest Experiment, one to turn the great Wheel, and one to hold Hands on the Globe. And the Effect after all but weak.5 Delor had a similar one, and invited me to see him exhibit to the Duchess of Rochefoucault, but the Weather being a little warm, he could perform nothing, scarce obtaining a Spark.6 This Inconvenience must have occasioned their Making fewer Experiments, and of course his not being so easily convinced. M. Le Roy, however, got early possession of the Truth, and combated for it with Nollet; yet I think the Academy rather favoured the latter.7 Le Roy will I suppose now confute this Translator, for I have just seen a Letter of his to Mr. Magelhaens, thanking him for sending so excellent an Electric Machine to France; (it is one of the Plate ones) which he has improv’d so as to produce the positive and negative Electricities separately or together at the same time, de façon (says he) qu’on peut faire toutes les Experiences possibles sur l’une ou l’autre de ces deux Electricités. Enfin on etoit si eloigné de connoitre les Phenomenes de ces deux Electricités ici, faute de Machines commodes de les démontrer, que beaucoup des Gens ont été etonnés de voir avec quelle évidence ils etablessent la distinction de ces deux electricités. &c. This Letter is of the 5th Instant.8 My best Wishes attend you and yours. I am ever, with great Respect, my dear Friend, Yours most sincerely

B F.

Dr Priestly

1“Fixed” or “factitious” air often meant any “air,” or gas, released by heat or chemical action from its fixed state in a substance, but for Priestley the term meant what we now call carbon dioxide. In the spring of 1772 he explained his method of “impregnating” or carbonating water to Sir George Savile, who put him in touch with the Admiralty. The method might sweeten water on a long voyage, it was thought, and perhaps reduce scurvy; and the Admiralty wished to use Cook’s second circumnavigation, which was about to begin, to test an antiscorbutic. Priestley demonstrated his method to the College of Physicians, which approved; he was then instructed to furnish the ships’ commanders and surgeons with details of the process, and on May 7 he did so. Soon thereafter he published his procedure in Directions for Impregnating Water with Fixed Air … (London, 1772). F. W. Gibbs, Joseph Priestley … (New York, 1967), pp. 57–60; Jack Lindsay, ed., Autobiography of Joseph Priestley … (Bath, [1970]), p. 95. Priestley assumed that Banks and Solander would go on the voyage; see his letter, which should be dated May 8, in Schofield, Scientific Autobiography, p. 131. In fact they did not go; see the annotation of Hume to BF above, Feb. 7.

2For Priestley’s description of his own machine see his History, II, 112–16; BF does not seem to have left any account of his “Philadelphia Machine.” Robert Symmer, F.R.S. (d. 1763), had differed with BF on electrical theory, but had asked for and received a copy of his machine; it was in Lord Morton’s hands by 1768. I. Bernard Cohen, Franklin and Newton … (Philadelphia, 1956), pp. 543–6; above, XV, 93 and n.

3Carlo Barletti, Nuove sperienze elettriche secondo la teoria del Sig. Franklin et le produzioni del P. Beccaria … (Milan, 1771).

4BF was right. The translator, Mathurin-Jacques Brisson (1723–1806), was Nollet’s successor at the college in Navarre; he was indeed a disciple, and by the time of the Abbé’s death in 1770, BF later remarked, was the only disciple. Autobiog., p. 244. In his Histoire de l’électricité traduite de l’anglois de Joseph Priestley … (3 vols., Paris, 1771) Brisson revived the old feud between his master and BF by arguing in a note (I, 21 n) that the former had first equated lightning with electricity.

5Priestley had the same opinion of the machine: History, II, 107–8.

6Delor and Dalibard, in 1752, had first publicized BF’s electrical theories in France by repeating his experiments. Ibid., I, 381–6; above, IV, 362, 424. We have found no other reference to Delor’s failure before the Duchess; it may have happened during either of BF’s visits to Paris, in 1767 or 1769.

7For the long dispute in the Académie des sciences see Cohen, op. cit., pp. 508–9.

8Jean-Hyacinthe de Magalhaens or Magellan (1723–90) was a former monk turned natural scientist and instrument-maker. DNB. He had a wide circle of scholarly friends and correspondents, for whom see Henry Guerlac, Lavoisier—the Crucial Year … (Ithaca, N.Y., [1961]), pp. 36–43. The machine that Jean-Baptiste LeRoy received from him provided further means of confirming BF’s theories; LeRoy described it at some length in a paper in the Mémoires of the Académie des sciences for 1772 (Paris, 1775), pp. 499–512. See also Walsh to BF below, June 21.

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