Credit: ©The Royal Society
    Image number: RS.15724

    The number of 'little animals' in a water drop

    Date
    20 May 1679
    Creator
    Antoni van Leeuwenhoek (1632 - 1723, Dutch) , Naturalist
    Object type
    Archive reference number
    Manuscript page number
    p1
    Material
    Dimensions
    height (page): 231mm
    width (page): 173mm
    Subject
    Biology
       > Anatomy
    Content object
    nature
       > animal
    Description
    A copy of a letter written by Antoni van Leeuwenhoek to Constantijn Huygens (senior). This is the copy that Van Leeuwenhoek made and sent to the Royal Society.

    The drawing shows a cubic inch ('cubicq duijm'), and his calculation on the same page is his estimation about the number of 'little animals' that can be found in a cubic inch of water. Van Leeuwenhoek bases his calculations on his observations of about 300 'little animals' in a water drop the size of a normal grain of sand.
    Object history
    The manuscript of the letter to Constantijn Huygens is lost. The present letter is an autographic copy sent by Leeuwenhoeck to the Royal Society in London. In the Leiden University Library there is a second copy, dated 21 May 1679, written by the same person who wrote the copy of the postscript to the letter of 25 April 1679. (Alle de brieven van Antoni van Leeuwenhoek, ed. by a committee of Dutch scientists, 17 vols [ongoing] (Amsterdam: Swets & Zeitlinger, 1939- ), III (1948), 52-67 (letter 47) (p. 53).)
    Related fellows
    Antoni van Leeuwenhoek (1632 - 1723, Dutch) , Naturalist
    Associated place
    <The World>
       > Europe
          > Netherlands
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