From William Alexander
ALS: American Philosophical Society
Auteuil 26 Sept 1778
The inclosed Paper Contains a short sketch of Dr. Blacks Doctrine of Latent heat.5 It is there applied only to a few phenomena but the Dr. has experiments to shew that it is also the Cause of vapour, and He Explains How Evaporation Generates Cold, and the whole Theory of fluidity. After you have red this short paper, When you meet with my B[rothe]r6 He will give you the Extent of the Doctrine and Inform you of the Experiments by which It is supported.
This Paper I got from one of Dr. Blacks Students for the use of Monsieur De Morveaux.7 I am with the most thorough Attachment Dear Sir Your most obedient humble Servant
Addressed: A Monsieur / Monsr Franklin / a Passy
Endorsed: W Alexander
Notation: 26. Sept. 1778.
5. Dr. Joseph Black (1728–99), professor of medicine and chemistry at the University of Edinburgh, and member of the eminent scientific societies of Europe, whose theory of latent heat formed the basis of modern thermal science. The theory was formulated as early as 1762, but never published; Black taught it in his lectures. DNB. BF had met him in Edinburgh in 1771 (XIX, 50) but there is no evidence that the two scientists corresponded.
6. Alexander John, for whom see XXIV, 199 n.
7. Louis-Bernard de Guyton de Morveau, the famous French chemist. Alexander had sent BF an advance copy of his most recent book the previous year: XXIII, 415, 440.