César-François Cassini

César-François Cassini (1714–1784), known as Cassini de Thury or Cassini III, was a French astronomer and geodesist, the son of Jacques Cassini. He belonged to the celebrated Cassini dynasty of astronomers, which directed the Paris Observatory for more than a century. His scientific career began at the height of the debate between Cartesians and Newtonians over the shape of the Earth. He took part in the geodetic operations conducted by his father in 1733–1734, then carried out a new measurement of the Paris meridian between 1739 and 1740, reaching the opposite conclusion to Jacques Cassini's: the Earth is flattened at the poles, in accordance with Newtonian predictions. This correction paved the way for the cartographic undertaking that was his principal work: the production of the first general map of France, drawn up by systematic triangulation and covering the entire territory. More than an astronomer, Cassini III established himself above all as a great geodesist and a leading cartographer. In 1771, he was appointed Director General of the Paris Observatory, with hereditary entitlement to the official residence, a privilege that until then had not been transferable. He died of smallpox on 4 September 1784.