Henry Oldenburg wrote to Leeuwenhoek acknowledging receipt of the letter of 1676-10-09

October 16, 1676

At the end of Leeuwenhoek's Letter 18 of 1676-10-09, Oldenburg wrote this note in French:

receu le 9. Octob. st. v. 1676.
Resp. le 16. Oct. d'avoir
receu cette lettre, par
M. Leibnitz, mais non pas
encor consideré.

st. v. - old style (Julian)

Oldenburg received Letter 18 when it was October 9 in London, October 19 in Delft. It thus took ten days to reach him. He responded a week later, on October 16, which was October 26 in Delft. He wrote that he received the letter but had not had time to study it in detail.

The reference to Leibniz is puzzling. Leibniz had recently arrived in England from Holland and was about to return to Germany via a visit to Spinoza in The Hague, only a few miles from Delft. Perhaps Oldenburg used the occasion to send his 16 October acknowledgement via Leibniz, who would have been very interested in the little animals that Leeuwenhoek reported in his letter of 9 October.