Letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft Signed letter Experiments using cinnabar (mercury sulphide); experiments with gunpowder; experiments with saltpetre (potassium nitrate); concerning the lengths of cannons; experiments with crab's eyes (lime contained in the stomach wall of crayfish) Original figures now no longer exist English translation see EL/L1/80 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 5, p 355 Translated extract printed in 'Philosophical Transactions', vol 17, no 200, p 754 22 January 1686