From William Henly
ALS: American Philosophical Society
Wednesday [June?] 17th. [1772?7]
Having Received an Account from Dr. Priestley that he could not verify my Experiment of ascertaining the direction of the Electric Matter in its passage through flame, I took the Liberty to call at your House with my Apparatus, in order to shew it you both positively and negatively, but I found you was gone into the Country. I then call’d and shew’d it to Mr. Nairne8 who signed a short Account which I drew up before him, that he was perfectly well satisfied with the Experiment both negatively and positively, and that it was a full and Convincing demonstration of the truth of your Hypothesis,9 this attested Account I transmitted to Dr. P. I shall be glad of an Opportunity to shew it you at your own House, as I have no Machine.1 I will not take up more then 10 Minutes of your time—only do me the favour to tell me what day and Hour I shall wait on you, and I will certainly be with you at your Appointment. I hope to get my Cyllender replaced soon, when the Honour of your Company will greatly oblige Sir your most Obedient and Humble Servant
P.S. I was not aware of your going into the Country so soon.
Addressed: To / Dr: Franklin / Craven Street / Strand
7. The letter describes one of a series of experiments performed principally in 1771–72: Phil. Trans., LXIV (1774), 389. The only clue to its date is that it was just after Henly found that BF was out of town. Wednesday the 17th narrows the possibilities within the period to three: April or July, 1771, or June, 1772. We have no record that BF was in the country during either of the months in 1771. On June 17, 1772, when he was about to leave on his journey to the north, he drafted the preceding document. If he set out immediately thereafter, Henly could have missed him, gone on to see Nairne, performed and repeated the experiment for him, and written BF about it, all on the same day. This possibility rests on a tissue of conjectures, but we can find no other date that seems as plausible.
8. [Henly’s note:] We had another able witness present, and repeated the Experiment many times both ways, to all our satisfactions.
9. Henly subsequently published his experiment in Phil. Trans., LXIV (1774), 397–8. It substantiated BF’s theory (above, XVIII, 19 n) about the direction of flow of electric fluid in the discharge of a Leyden jar, and refuted Benjamin Wilson’s hypothesis (Phil. Trans., LI , 320) that flame stored or diminished the charge. See also Priestley, History, II, 204–5.
1. His glass cylinder was broken, as indicated below. Our guess is that BF did not arrange a meeting until the evening before Henly’s note to him below, under Oct. 28.