Benjamin Franklin Papers

From Benjamin Franklin to Jean-Baptiste LeRoy, 22 June 1773

To Jean-Baptiste LeRoy

ALS (draft): American Philosophical Society

London, June 22. 1773

However glad I am of the Occasion, I forbore indulging my self in the Pleasure of congratulating by the first Post my dear double Confrere, on his Election into our Royal Society; because Mr. Walsh undertook to give you the Information,5 which would make a Second Expence unnecessary, and I saw I should soon have this opportunity by the favour of M. Poisonnier.6 I rejoice in the Event, as you seemed anxiously concern’d about it, and we have done ourselves Honour, in distinguishing and associating a Merit so universally known and acknowledg’d.

I am pleas’d to hear you are engag’d in the Consideration of Hospitals.7 I wish any Observations of mine could be of Use to you, they should be at your Service. But ’tis a Subject I am very, little acquainted with. I can only say, that if a free and copious Perspiration is of use in Diseases, that seems, from the Experiments I mention’d to M. Dubourg,8 to be best obtain’d by light covering and fresh Air continually changing: The Moisture on the Skin when the Body is warmly covered, being a Deception and the Effect not of greater Transpiration, but of the Saturation of the Air included under and in the Bedclothes, which therefore can absorb no more, and so leaves it on the Surface of the Body. From those Experiments I am convinc’d of what I indeed before suspected, that the Opinion of Perspiration being check’d by Cold is an Error, as well as that of Rheums being occasion’d by Cold. But as this is Heresy here, and perhaps may be so with you, I only whisper it, and expect you will keep my Secret. Our Physicians have begun to discover that fresh Air is good for People in the Small Pox and other Fevers. I hope in time they will find out that it does no harm to People in Health.

We have nothing new here in the philosophic Way. I shall like to hear how M. Lavoisier’s Doctrine supports itself as I suppose it will be controverted.9 With the greatest Esteem, I am ever, Dear Sir Yours most affectionately

B Franklin

Enclos’d I send you some Pamphlets relative to our American Affairs for your Amusement. Sir Jno Pringle bids me present his Compliments. He interested himself much in the Election.

M. Le Roy.

[Note numbering follows the Franklin Papers source.]

5LeRoy, a leading member of the Académie royale des sciences, had been elected to the APS in January: above, XIX, 278. On Sept. 5, 1772, he had been nominated for the Royal Society by some of its French members; a number of F.R.S. in England, including John Walsh and BF, supported the nomination, and he was elected on June, 10, 1773. From the letter of nomination in the Royal Society. Walsh doubtless brought the letter when he returned to England on Sept. 17 (above, XIX, 295 n), and wrote LeRoy after the election.

6For Poissonnier see above, XIX, 328 n. He also took Dubourg a letter from BF and a packet from Rush; see below, BF to Dubourg, June 29, and to Rush, July 14.

7BF must be referring to a LeRoy letter, now lost, later than that of April 19. As a physician the Frenchman was particularly interested in the condition of hospitals, a matter that was at the moment much to the fore. The Hôtel-Dieu in Paris had been partially burned in December, 1772, and the following May the King had ordered the hospital transferred to two others. These developments led LeRoy to work on a project, which dragged on for years and never came to fruition, for rebuilding the Hôtel-Dieu on a novel design. Louis S. Greenbaum, “Tempest in the Academy: Jean-Baptiste Le Roy, the Paris Academy of Sciences and the Project of a New Hôtel-Dieu,” Archives internationales d’histoire des sciences, XXIV (1974), 122–40.

8In his first letter to Dubourg above, March 10; see also Rush to BF, May 1.

9The “Doctrine” was indeed controversial, and turned out to be epoch-making. Priestley’s work, about which LeRoy had been skeptical the previous autumn (above, XIX, 308), stimulated Lavoisier in his now famous experiments on combustion; they demonstrated that substances which increase in weight when burned do so by absorption from the atmosphere. His sealed note of this discovery, deposited with the Académie in November, 1772, was opened and read on May 5, 1773, after further experiments had confirmed its findings. Douglas McKie, Antoine Lavoisier … (New York, [1952]), pp. 101–3. Those findings were irreconcilable with the phlogiston theory, of which Priestley was the outstanding protagonist; hence BF’s interest in the controversy.

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