César-François Cassini de Thury (17 June 1714 – 4 September 1784), also called Cassini III or Cassini de Thury, was a French

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

and

cartographer Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an ...

Biography

Cassini de Thury was born in

Thury-sous-Clermont Thury-sous-Clermont (, literally ''Thury under Clermont'') is a commune in the Oise department in northern France. See also * Communes of the Oise department The following is a list of the 679 communes of the Oise department of France. The ...

, in the

Oise Oise ( ; ; pcd, Oése) is a department in the north of France. It is named after the river Oise. Inhabitants of the department are called ''Oisiens'' () or ''Isariens'', after the Latin name for the river, Isara. It had a population of 829,41 ...

department, the second son of

Jacques Cassini Jacques Cassini (18 February 1677 – 16 April 1756) was a French astronomer, son of the famous Italian astronomer Giovanni Domenico Cassini. Cassini was born at the Paris Observatory. Admitted at the age of seventeen to membership of the French ...

and Suzanne Françoise Charpentier de Charmois. He was a grandson of

Giovanni Domenico Cassini Giovanni Domenico Cassini, also known as Jean-Dominique Cassini (8 June 1625 – 14 September 1712) was an Italian (naturalised French) mathematician, astronomer and engineer. Cassini was born in Perinaldo, near Imperia, at that time in the ...

, and would become the father of Jean-Dominique Cassini, Comte de Cassini. In 1739, he became a member of the

French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at ...

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 Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemati ...

. He succeeded to his father's official position in 1756 and continued the hereditary

surveying Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ...

operations.Jonathan Powell, ''From Cave Art to Hubble: A History of Astronomical Record Keeping'', (Springer Nature Switzerland AG, 2019), 115 In 1744, he began the construction of a great topographical map of France, one of the landmarks in the history of

cartography Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an i ...

. Completed by his son Jean-Dominique, and published by the

Académie des Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at ...

from 1744 to 1793, its 180 plates are known as the

Cassini map The Cassini Map or Academy's Map is the first topographic and geometric map made of the Kingdom of France as a whole. It was compiled by the Cassini family, mainly César-François Cassini (Cassini III) and his son Jean-Dominique Cassini (Ca ...

( 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), an

arc measurement Arc measurement, sometimes degree measurement (german: Gradmessung), is the astrogeodetic technique of determining of the radius of Earth – more specifically, the local Earth radius of curvature of the figure of the Earth – by relating the la ...

correction of the

Paris meridian The Paris meridian is a meridian line running through the Paris Observatory in Paris, France – now longitude 2°20′14.02500″ East. It was a long-standing rival to the Greenwich meridian as the prime meridian of the world. The "Paris meri ...

( Dunkirk-Collioure arc measurement (Cassini de Thury and de Lacaille)); ''Description géométrique de la terre'' (1775); and ''Description géométrique de la France'' (1784), which was completed by his son (""). César-François Cassini de Thury died of

smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) c ...

in Paris on 4 September 1784.

Works

*''La méridienne de l’Observatoire Royal de Paris'' (1744) *''Description géométrique de la terre'' (1775) *''Description géométrique de la France'' (1784) *

Bibliography

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)

References

External links

List of online works
available on Gallica
Cassini map online on EHESS site

cartocassini site
gathers old maps and allows for various manipulations, notabl

Cassini map in Géoportail (IGN)

* ttps://bibnum.obspm.fr/ Paris Observatory digital library {{DEFAULTSORT:Cassini De Thury, Cesar Francois 1714 births 1784 deaths Giovanni Domenico Cassini Scientists from Paris 18th-century French astronomers 18th-century French cartographers Members of the French Academy of Sciences Fellows of the Royal Society Deaths from smallpox Infectious disease deaths in France French geodesists