Translation of a letter, from Antoni van Leeuwenhoek to the Royal Society Observations of the colony-forming flagellate 'Anthophysa vegetans' from Delft canal water; observations of dissolving silver in aqua fortis (nitric acid and sulphuric acid) and gold in aqua regia (mixture of nitric acid and hydrochloric acid); observations of the forms in which gold is precipitated from the solution; reasons why there is little duckweed on the surface of water in cold weather Translator mistakenly wrote that the letter was from John Chamberlayne Original is EL/L3/49 English translation printed in 'Philosophical Transactions', vol 23, no 286, p 1430 1703