Bochart De Saron, Jean-Baptiste-Gaspard

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Bochart De Saron, Jean-Baptiste-Gaspard

(b. Paris, France, 16 January 1730; d. Paris, 20 April 1794)

astronomy.

Bochart, whom Laplace aptly described as an enlightened amateur scientise, followed family tradition by choosing a legal career and by having a keen interest in astronomy. His prominent name, his scientific competence, and his generosity to academicians (e.g., he financed the publication of Laplace’s Théorie du movement et de la figure élliptique des planètes) led to his election, in 1779, as an honorary member of the Académie des Sciences and to his appointment, after the death of Camus, as one of the directors of Jacques Dominique Cassini’s project, the Carte de France. He approached science with concrete images rather than with abstractions, through mechanics rather than through mathematics, and with practical interests rather than with theoretical ones.

At an early age Bochart successfully tried his hand at making reflecting telescopes, and astronomical instruments then became his passion. He spared neither his free time nor his wealth in creating one of Europe’s largest and finest collections. Renowned craftsmen constructed his instruments: for example, John Dolland made an early achromatic telescope for him, and Jesse Ramsden, a very accurate degree cutting machine. Bochart placed his collection at the disposition of the academicians: Jean Delambre, Pierre Méchain, Guillaume Le Gentil, Achille Dionis du Séjour, and Charles Messier.

Bochart calculated the orbits of comets on the basis of observations furnished by his long-time collaborator, Messier. The observed positions were few and close togehter; this presented special difficulties for Bochart, who used Boscovich’s method, which he simplified and mechanized in his calculations. His predictions vastly aided Messier in finding the comets after they had disappeared behind the sun. The supposition that Bochart was forced to make when trying to calculate the orbit of Herschel’s comet—discovered in 1781—played an important role in identifying it as the planet Uranus. He supposed that it followed a circular orbit with a radius equal to twelve times the distance of Saturn from the sun. This proved accurate, and Laplace then calculated the precise elliptical orbit. Bochart, who became the First President of the Parliament of Paris a few months before the outbreak of the French Revolution, lost his head during the reign of terror of the Committee of Public Safety.

BIBLIOGRAPHY

I. Original Works. Bochart’ astronomical observations are in Mémories de l’Académie Royale des Sciences, année 1769, 421, 429; ibid., année 1770, 232; année 1774, 19; ibid., année 1775, 217; and ibid., année 1776, 450. An orbital calculation is “Comèt observée en 1779,” in Connaissance des Temps pour… 1782 (paris, 1779), 395.

II. Secondary Literature. More information on Bochart and his work may be found in Jacques Dominique Cassini, “Découverte de la planèt Herschel” in Connaissance des temps… 1786 (Paris, 1783), 3–4; Cassini published his eulogy of Bochart separately and in Mèmories pour servir à history des sciènces (paris, 1810), 373–391; J-J. DeLalande. “Historic de l’astronomic pour 1794,” in Connaissance des temps… pour l’ année sextile VIIe (Paris, 1797), 282–318, esp. 310–311 for a eulogy of Bochart, which was also published in DeLalande’s Bibliographie astronomique (Paris, 1803), 752–754. Boscovich gives his method in “De orbits cometarum deteminandis, ope trium observationum parum a se invicem remotarum,” in Mémories de mathématique et de physique (Académe des Sciences), VI (paris, 1774), 198–215, 401–434. Detailed information on Bochart’ family is given in P. Humbert, “Les astroonomes françs de 1610 à 1667,” in Société d’Études Scientifiques et Archéologiues de Draguignan, Mémories, 63 (1942), 1–72; L. Moréri, s.v. Bochart, Le grand dictionnarie historique (paris, 1759).

Robert M. Mckeon