Cassini de Thury, César-François

Alternate Name

Cassini III

Born Thury near Clermont, (Oise), France, 17 June 1714

Died Paris, France, 4 September 1784

Cassini de Thury was best known as a cartographer and was a key figure in the controversy over the shape of the Earth. He was the son of Jacques Cassini (Cassini II) and Suzanne-François Charpentier de Charmois. César-François was educated at the family home in the Paris Observatory by his granduncle Giacomo Maraldi . Elected to membership of the Académie des sciences in 1735, he succeeded his father as director of the Paris Observatory.

Cassini began his career just as the controversy over the shape of the Earth reached its peak, with the Cartesian concept seemingly in the ascendancy. At this stage he was loyal to the family’s Cartesian leanings, that the Earth is elongated along the line of its poles. In 1733/1734, he, with others, assisted his father to determine the arc of the great circle perpendicular to the meridian of Paris, a survey necessary for the mapping...