Letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft Signed autograph Observations of protozoa in rain water; observations of air bubbles in rain water; observations of the circulation of blood in an eel Read to the Royal Society on 27 May 1702 English translation see EL/L3/45 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 14, p 135 English translation printed in 'Philosophical Transactions', vol 23, no 279, p 1152 28 April 1702