Translated extract of a letter, from Antoni van Leeuwenhoek to the Royal Society Observations of the compound eye of a beetle and calculations about the number of facets; observations through the human cornea; observations of the legs, cornea and ommatidia of a drone fly; observations of the brain of a gnat Translation of EL/L3/5 Translated extracted printed in 'Philosophical Transactions', vol 20, no 240, p 169 1698