Benjamin Franklin Papers

To Benjamin Franklin from William Henly, [after 25 May 1774?]

From William Henly

ALS (incomplete): American Philosophical Society

[After May 25?, 17745]

[Missing] ourselves without making Mr. W—s experiment. But to be serious; unluckily for that Gentleman I have drawn no conclusion from his favourite experiment, except it be this, that a point will not invite a stroke of lightning upon it, at 12 times the distance of a knob.6 The chains happen’d to be both of the same wire, and length.7 Whoever doubts whether the ends of the bars at St. Pauls pass through the pavement, may please to take a walk to the stone gallery and see. Mr. Gould did not discover the amazing smell of sulphur till the next day after the stroke. He keeps a snuff shop.8

[He] told Mr. Bell he was of opinion St. Pauls had not [been stru]ck,9 I am Dear Sir most cordially yours

W Henly

[Note numbering follows the Franklin Papers source.]

5Henly was writing about Wilson’s Further Observations upon Lightning, a note on which immediately precedes this letter and explains our dating. He might have been referring to the paper read before the Royal Society the previous February, which became the pamphlet (above, XX, 166–7); but his remark about the chains, so similar to his marginal comment on the pamphlet quoted below, makes us think that the letter came after publication.

6Wilson’s favorite experiment was the one by Henly discussed above, XIX, 261 n.

7In his pamphlet Wilson attacked Henly for not giving the exact length of the two chain conductors used in the experiment, because extra links in one could have skewed the results to support Henly’s theory. “None but Mr. W —,” Henly wrote in the margin of his copy, “would ever have supposed them otherwise than they really were, viz made of the same wire, and of a length exactly equal” (p. 4). BF acquired the copy with Henly’s marginalia, and it is bound with his own copy in the Yale University Library.

8Richard Gould was Dean’s verger of St. Paul’s: Gent. Mag., LVI (1786), 440. The morning after a storm in 1772 (above, XIX, 426 n) he had examined the conductors in the Cathedral and found them badly discolored; at the same time, he added later, he had noticed the smell of sulphur (now known to be that of ozone), which accompanies a discharge. On this evidence Wilson concluded that the building had been struck: Observations upon Lightning … (London, 1773), pp. 13–14. Henly thought the conclusion preposterous: the smell could not have survived for eighteen hours in the open air and, even if it had, could not have been detected by a man who kept a snuff shop. Phil. Trans., LXIV (1774), 148–51; Henly’s marginalia cited above, p. 25.

9For our conjecture about Bell’s identity see above, XIX, 442 n. He had visited the Cathedral to investigate Gould’s observations: Henly’s marginalia just cited, p. 23.

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