Wrote Letter L-040 of 1676-10-09 to Henry Oldenburg about little animals in various waters and spice infusions, the relationship of their shape to taste, and whether there were little animals in the air

October 9, 1676
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Text of the letter in the original Dutch and in English translation from Alle de Brieven / The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren

The original manuscript on 18 folio pages, written by a copyist and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1851. Early Letters L1.22). On the last page of text, Oldenburg wrote, "receu le 9. Octob. st. v. 1676. / Resp. le 16. Oct. d'avoir / receu cette lettre, par / M. Leibnitz, mais non pas / encor considere." Oldenburg's English translation is Early Letters L1.23.

An excerpt was published in Philosophical Transactions, vol. 12, no. 133, dated 25 March 1677. See Publication history below.

Leeuwenhoek wrote this letter to Henry Oldenburg about

  • his discovery of five different micro-organisms - one possibly bacteria - in pepper-infused water
  • his experiments with rain-, well-, moat-, sea-, and river-water, and infusions of various spices
  • an account of the structure of a peppercorn, wheat, ginger; whether or not there are organisms in the air.

This is Leeuwenhoek's most famous letter, the one that made his name known world-wide. The bulk of Dobell's "Little Animals" is devoted to a translation and annotation of it.

He began it by noting that he had not received a reply to his two previous letters. The rest of the letter is 145 observations of 19 different series of liquids, about half of them infused with various spices.

Other than the observation from the previous September, they were all conducted from mid-April to the end of September, 1676. Some of the observations were one-time only. Many series lasted for a month or two. The longest spanned 18 weeks. With such a quantity of data, how should he organize it?

A month later, Leeuwenhoek wrote to Constantijn Huygens (AB/CL 28), enclosing a copy of much of this letter of October 9:

I have couched my observations in the form of a journal, merely that they be better credited in England and elsewhere, the more so because the Secretary, Mr. Oldenburg, wrote to tell me some time ago that there actually are learned gentlemen in Paris and elsewhere who do not believe what I saw.

The letter was written in a hand other than his, probably from his notes. It would take hours to make a fair copy of such a long letter, and Leeuwenhoek was suddenly busy with managing Vermeer's estate. That appointment as curator at the end of September may well have been what caused him to stop his series of observations and give his notes to a copyist.