Letter, from Juan Cruzado to Henry Oldenburg Cruzado discusses: - a new place for the prime meridian of the globe - testing the equal revolution of the natural day with his pendulum clock - ascertaining the moon's place on land and at sea - the longitude of Seville These points are reiterated in EL/C2/2 Read to the Royal Society on 28 October 1675 Printed as by "a Spanish Professor of mathematics" in 'Philosophical Transactions', vol 10, no 118, p 425 20 August 1675