Reference Work Entry

Biographical Encyclopedia of Astronomers

pp 363-364


Camus, Charles-Étienne-Louis

  • Monique GrosAffiliated withUPMC, Paris 06, and CNRS, UMR 7095, Institut d’astrophysique de Paris Email author 

Born Crécy-en-Brie near Paris, France, 25 August 1699

Died Paris, France, 4 May 1768

As a member of the Académie royale des sciences, Charles-Étienne-Louis Camus took an active part in the scientific life of eighteenth-century Paris and is particularly known for his participation in the astronomical and geodesic program to define the shape of the Earth. He also contributed to clockmaking and mechanics.

Camus was the son of a surgeon. From an early age, he showed a special gift for mathematics, while being clever with his hands, making and repairing iron or wood objects. He persuaded his parents to let him study in the Collège de Navarre in Paris. After leaving the college, Camus continued mathematical studies on his own, later with the aid of Pierre Varignon, a member of the academy. He also began studies in geometry, civil and military architecture, mechanics, and astronomy.

In 1727 Camus presented a dissertation to the academy on ships’ masts; this work was appreciated by the academy, which decided to include it among the works to be published. Camus also was rewarded with half the prize money. On 5 August 1727 the academy elected him an adjoint-mécanicien member. In the following year, Camus submitted a memoir in favor of the idea of vis viva, which was then being debated. Until 1730, the academy records refer to him as the abbé Camus. He must have left the priesthood about that time, as he married Marie-Anne-Marguerite Fourrier in 1733. They had four daughters, only the eldest of whom reached adulthood.

In 1730 Camus was appointed as a professor of geometry in the Royal Academy of Architecture, being named its secretary 3 years later. In 1733 Camus presented a memoir on toothed wheels and the gears, which was a generalization of some work previously presented by Philippe de La Hire . He also showed talent in dealing with clock and watch-making questions. In 1733 Camus and Alexis-Claude Clairaut were both elected as associate members of the Académie royale des sciences.

During these years, the French scientific establishment debated the shape of the Earth and planets. As previous measurements by Giovanni Cassini disagreed with the Newtonian theory, the academy ordered two expeditions to measure the length of a degree along the meridian, one to Peru(now Equator) (1735) and one to Lapland (1736–1737). Camus participated in the latter, which was led by Pierre de Maupertuis . The abbé Réginald Outhier ’s account of the expedition, Journal d’un voyage au Nord, en 1736 & 1737, appeared in Paris in 1744. It recounts Camus’ efforts as a clockmaker, mechanic, and engineer, all of which were invaluable to the success of the expedition into these distant and inhospitable areas. Camus erected the expedition’s lodgings, assembled and regulated its measuring devices, and manufactured clocks for various experiments.

As the Lapland results were equivocal, further expeditions were arranged. Camus and his partners of the Lapland team made observations to determine again the length of the arc of the meridian in the vicinity of Amiens made by Jean Picard in 1669/1670. Camus, with the astronomers Pierre Bouguer, César Cassini de Thury, and Alexandre Pingré , was among the eight academicains commissioned by the Royal academy of Science to operate and verify the meridian degree length between Paris and Amiens already measured by Abbot Jean Piccard in the 1669–1670’s; especially the lenght of the base of the triangulation operations, between Villejuive and MontlhÕry was measured again in 1756. He was too involved in the operations of the Carte de France (known as the Cassini Map).

In 1745 Camus undertook, along with Jean Hellot, some metrological work. From that time Camus was heavily involved in the routine work of the academy, examining memoirs and machines submitted to it, attending meetings, undertaking evaluation missions, and participating in different projects. In 1763, Camus was in the official delegation of the Academy who went to London to visit John Harrison and examine his timepieces.

Camus was designated as a pensioner–geometer member in the academy in 1741, as sous–directeur in 1749 and 1760, and directeur in 1750 and again in 1761. In 1745 he was appointed by the academy to be an examiner in the royal engineering schools, a position that led him to write a mathematics textbook. The first three parts, on arithmetic, geometry, and mechanics, were published; the drafts concerning hydraulics were found in his home after his death. This textbook, even with some defects, was used widely in French engineering schools. Camus was elected to the Royal Astronomical Society in 1765.

Camus caught a bad flu during the winter of 1766 as he traveled to Metz to organize an examination; he was recovering when the news of his daughter’s death late in 1767 came to him. Camus was reported to be an upright man, apolitical, plain in discussion, although sometimes quick to retort. Although not a scientist of the first rank, Camus was an important participant in the work to establish the figure of the Earth.

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