CESAR FRANgOIS CASSINI or CASSINI DE THURY (1714-1784), son of Jacques Cassini, was born at the observatory of Paris on June 17, 1714. He succeeded to his father's official employments, continued the hereditary surveying operations, and began in the construction of a great topographical map of France. The post of director of the Paris observatory was created for his benefit in 1771, when the establishment ceased to be a dependency of the Academy of Sciences. Cassini de Thury died at Thury on Sept. 4, 1784. His chief works are : Meridienne de l'observatoire de Paris 0744), Description geometrique de la terre (I775), and Description geometrique de la France (1784).