Wrote Letter L-054 of 1677-03-23 to Henry Oldenburg about the quantity of little creatures in one drop of water

March 23, 1677
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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 four folio pages, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1854. Early Letters L1.25). A Latin translation of the letter, sent to London by Leeuwenhoek, is also preserved at the Royal Society (MS. 1855. Early Letters L1.26).

An excerpt was published in Philosophical Transactions, vol. 12, no. 133, dated 23 April 1677. See Publication history below.

Leeuwenhoek wrote this letter to Henry Oldenburg about his method of counting so vast a number of living creatures in one drop of water. He announced further observations on this subject. He also complained about not getting published. He was replying to Oldenburg's Letter L-053 of 22 February (12 February O.S.) and Letter L-053 of 4 March (22 February O.S.)

The methodology for calculating the number of living organisms in a drop of water. States that he sends a Latin translation of his letter (see EL/L1/26).

He also included a Latin translation with his Dutch letter (Royal Society EL/L1/26). See the fragment labeled 21a in the photo below.

The photo below of Leeuwenhoek's handwritten manuscript is from the first of the four volumes of Leeuwenhoek's original letters in the archives of the Royal Society. The photo was taken by Mike Peel < MikePeel.net > and is available on Wikimedia Commons.