Constantijn Huygens wrote Letter L-082 to Leeuwenhoek that his son Christiaan’s new book Dioptrica is about to be published

This letter is known only by reference in another letter.

In this letter, Constantijn Huygens writes to Leeuwenhoek that his son Christiaan’s new book Dioptrica is about to be published.

The third part of Christiaan Huygens’s La Dioptrique on telescopes and microscopes was not published until 1685. For an explanation of the delay, see notes 5 and 6 to Leeuwenhoek’s Letter L-084 of 15 May 1679 to Constantijn Huygens, Collected Letters, vol. 3.

Huygens’s previous letter to Leeuwenhoek is Letter L-076 of 23 December 1678 about little animals in pepper-water and the scales on the wings of butterflies. Leeuwenhoek responded directly to each of Huygens’s concerns in Letter L-077 of 28 December 1678. In Letter L-081 of 27 April 1679, also written to Huygens before the present letter, he discussed the size of particles of water and compared the size of microorganisms to a grain of sand; he included his mathematical reasoning.

Leeuwenhoek replied to the present letter with Letter L-085 of 20 May 1679, in which he continued his discussion in Letter L-081, this time speculating on microscopic and submicroscopic dimensions, leading to the conclusion that the component parts (molecules) of water are unimaginably small.

Huygens’s next and last letter is Letter L-167 of 17 December 1685, in which he praises the historican importance of Leeuwenhoek’s discovery of sperm. Leeuwenhoek did not reply to that letter, but he included it in its entirety within Letter L-199 of 24 August 1688.