Robert Hooke wrote Letter L-068 to Leeuwenhoek about how he verified Leeuwenhoek’s observations of little animals in a pepper infusion

February 11, 1678

Hooke dated the letter in Old Style. 1 February in London was 11 February in Delft. The Royal Society copyist erroneously gave it the date of 1 December 1677. In the Royal Society’s Early Letters, this letter is dated 1 February 1677/8 O.S. with the note, “Listed in ‘Catalogue of Manuscript Letters’ as December 1677.”

Hooke wrote to Leeuwenhoek about how he verified Leeuwenhoek’s observations of little animals in a pepper infusion as well as an account of other little animals observed in the infusions of several grains in rain water. He noted that the president and members of the Royal Society were surprised and satisfied.

On 15 November 1678 O.S., Hooke was finally able to show the members of the Royal Society little animals in pepper water, just as Leeuwenhoek had reported a year earlier in his letter of 9 October 1676. See Birch, The History of the Royal Society of London, vol. III, p. 352. For Hooke’s more complete account of the events related to L. during the Society’s meetings of November 1677, see The Hooke Folio Online, CELL/RS/HF_107-112.

Leeuwenhoek would instead send his next six letters to the Royal Society to Nehemiah Grew. See the Remarks to Grew’s Letter L-066 of 11 January 1678 for an overview of their correspondence.


The manuscript is to be found in London, Royal Society, Early Letters H3.54, 1 page. A copy is to be found in the Royal Society’s Letter Book Original, supplement 4 GH, pp. 367-68. It was never published.

A Letter from Mr. Hooke to Mr.Leeuwenhoek verifying his Observations of Anmalcula in Pepper Water, and adding an account of others observed in the Infusions of several Grains in Rain Water.


London, Dec'r 1: 1677

    The papers you directed to the Lord BROUNKER were read at a full meeting of the Royal Society, and very kindly accepted by the members thereof: and they have ordered me to return you both their thanks for so freely communicating your observations, and also an account of what hath been here done in order to verify your observation concerning the small animals you have first discovered in pepper water .

    Having steeped then in rain water, pepper, wheat, barly, oats, peas and several other grains, and having fitted up some microscopes, which had lain a long while neglected, I having been by other urgent occasions diverted from making further inquiries with that instrument; I began to examine all those several liquors and though I could discover divers very small creatures swimming up and down in every one of these steepings, and even in rain itself, and that they had various shapes and differing motions; yet I found none so exceedingly filled and stuffed as it were with them, as was the water in which some corns of pepper had been steeped. Of this the president and all the members present were satisfied, and it seem’d very wonderfull that there should be such an infinite number of animals in so imperceptible a quantitiy of matter: that these animals should be so perfectly shaped and endowed with such curious organs of motion as to be able to move nimbly, to turn, stay, accelerate and retard their progress at pleasure. And it was not less surprizing to find that these were gigantick monsters in comparison of a lesser sort which almost filled the water.

    Sir, what further discoveries my time will permit to make I shall by the next send you. In the mean time (not doubting but that you have many already by you, and that you will daily increase them) I do hereby assure you that if you please to communicate any other to the Royal Society by mine or any other hand, you will very much oblige them, and more particularly, your very great admirer and honorer .


    You may please to direct your letter thus: To Mr. ROBERT HOOKE Secretary of the Royal Society at Gresham College, in London.