César-François Cassini de Thury

Cassini de Thury was born in Thury-sous-Clermont, in the Oise department, the second son of Jacques Cassini and Suzanne Françoise Charpentier de Charmois.[1] He was a grandson of Giovanni Domenico Cassini, and would become the father of Jean-Dominique Cassini, Comte de Cassini.[2]

In 1739, he became a member of the French Academy of Sciences as a supernumerary adjunct astronomer, in 1741 as an adjunct astronomer, and in 1745 as a full member astronomer.

In January, 1751 he was elected a Fellow of the Royal Society.[3]

He succeeded to his father's official position in 1756 and continued the hereditary surveying operations.[4] In 1744, he began the construction of a great topographical map of France, one of the landmarks in the history of cartography. Completed by his son Jean-Dominique, Cassini IV and published by the Académie des Sciences from 1744 to 1793, its 180 plates are known as the Cassini map (fr).

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 French Academy of Sciences.

His chief works are: La méridienne de l’Observatoire Royal de Paris (1744), a correction of the Paris meridian; Description géométrique de la terre (1775); and Description géométrique de la France (1784), which was completed by his son ("Cassini IV").

César-François Cassini de Thury died of smallpox in Paris on 4 September 1784.

• La méridienne de l’Observatoire Royal de Paris (1744)
• Description géométrique de la terre (1775)
• Description géométrique de la France (1784)
• César-François Cassini de Thury (1775). Relation d'un voyage en Allemagne. Paris: Imprimerie Royale.

D. Aubin, Femmes, vulgarisation et pratique des sciences au siècle des Lumières : Les Dialogues sur l’astronomie et la Lettre sur la figure de la Terre de César-François Cassini de Thury, Brepols (2020)

• Cassini projection

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Cassini". Encyclopædia Britannica (11th ed.). Cambridge University Press.

• List of online works available on Gallica
• Cassini map online on EHESS site
• cartocassini site, gathers old maps and allows for various manipulations, notably finding all Cassini maps in Gallica
• Cassini map in Géoportail (IGN)
• Cassini map superimposed over Google Maps' map of France - David Rumsey
• Paris Observatory digital library