Benjamin Franklin Papers

To Benjamin Franklin from Emanuel Mendes da Costa, 20 July 1765

From Emanuel Mendes da Costa6

ALS: Historical Society of Pennsylvania

Royal Society house 20 July 1765


The Committee for Mr. Canton’s Experiments7 meet Again on Tuesday next 23 Instt at 11 O’Clock precisely to prosecute the same. I am Sir Your humble Servant

Emanuel Mendes da Costa8

[Note numbering follows the Franklin Papers source.]

6Emanuel Mendes da Costa (1717–1791), son of a London merchant, was trained as a notary, became a student of conchology, mineralogy, and fossils, and during his checkered career published several books and papers on these subjects. Elected F.R.S. in 1747 and F.S.A. in 1752, he was imprisoned for debt in 1754, but through the efforts of Peter Collinson and other friends was appointed clerk and assistant secretary of the Royal Society in 1763. “Detected in various acts of dishonesty,” he was dismissed in 1767 and spent the next five years in King’s Bench Prison. Many of his MSS are in the British Museum. DNB; Charles R. Weld, A History of the Royal Society (London, 1848), II, 562.

7John Canton’s experiments on the compressibility of water (above, XI, 244–6), refuted some earlier experiments and provoked criticism when reported to the Royal Society. Its Council appointed a committee of twelve, including BF, to observe a repetition of the experiments. Rough minutes of the committee and other records of the Society show that a quorum of the committee met at least nine times between June 17 and Nov. 21, 1765, at six of which meetings BF was present. On the last of these sessions the committee resolved by ballot that it found Canton’s experiments verified, that the hypothesis of the compressibility of water would account for the phenomena observed, and that no experiments or reasoning hitherto presented to the committee would account for these phenomena from any other cause. The Council of the Society thereupon voted unanimously, Nov. 28, 1765, to confer the Copley Medal for 1764 upon Canton for these experiments. Royal Society, M.S. 141; Council Minutes, V, 140–3; Journal Book, XXV, 651–60.

8On the verso is written in the hand of Robert Gilmor, Jr. (1774–1848), a Baltimore autograph collector: “Note to Dr. Franklin from the Secretary [sic] of the Royal Society—given to me by Mr. Sparks in 1827—R G.”

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