Translation of a letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft 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 Translation of EL/L1/79 Extract printed in 'Philosophical Transactions', vol 17, no 200, p 754 1686