Pezenas, Esprit

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(b. Avignon, France, 28 November 1692; d. Avignon, 4 Febuary 1776)

hydrography, astronomy, physics.

Pezenas was the son of E. F. Pezenas, a notary and court clerk, and Gabrielle de Rivieres. He entered the Jesuit collège in Avignon at the age of ten and began his novitiate when he was seventeen. At the conclusion of his studies he taught first in Lyons and then at the Jesuit college in Aix. (He taught physics in 1724 and 1726, logic in 1725, and metaphysics in 1727.) In 1728 Pezenas was named professor of hydrography at the Ecole Royale d’Hydrographie at Marseilles and was assigned to teach the galley officers. He held this post until the school was closed in 1749, when he was appointed director of the Observatoire Ste-Croix in Marseilles, a Jesuit establishment that later became Observatoire Royal de la Marine. In 1763, upon the suppression of the Jesuit order in France, Pezenas retired to Avignon, where he died at the age of eighty-three. He was a member of the Academie de Marine and, from 1750, a corresponding member of the Académie Royale des Sciences.

Besides giving highly regarded lectures, Pezenas published a number of works on hydrography and sailing. Notable among these were treatises on piloting, a work on gauging barrels and ships, and several treatises on nautical astronomy in which he set forth innovations in the use of such instruments as the vernier, the azimuth compass, and the octant. His interest in the determination of longitudes led to several papers on the subject. Assigned to design and estimate the cost of a canal that would supply Marseilles with water taken from the Durance River, he conducted the necessary surveying. Meanwhile, he had also become increasingly interested in astronomical observation. He paid for some of his observatory equipment, and in 1749 the king granted him the services of two associate astronomers, both Jesuits. He presented his first observations (including the determination of the latitude of Marseilles) in 1731 in the Memoires de Trevoux (Memoires pour servir a l’histoire des sciences et des beaux arts); the others appeared in Histoire de l’Academie Royale des Sciences.

Pezenas played a major role in the diffusion in France of important works by English scientists, especially in mathematics and optics. Although his scientific achievements were modest, Pezenas was an effective popularizer who made skillful use of the scientific and technical knowledge of his time.


I. Original Works. Pezenas’s main publications are listed in J. M. Quérard, La France littéraire, VII (Paris, 1835), 111–112; Poggendorff, II, 422–423; and A. de Backer, A. de Backer, and C. S. Sommervogel, Bibliothéque de la Compagnie de Jésus, VI (Brussels-Paris, 1845), 647.

His principal works are Éléments de pilotage (Marseilles, 1733); Pratique du pilotage (Marseilles, 1741); La théorie et la pratique du jaugeage (Avignon, 1749); Astronomie des marins... (Avignon, 1766); and Histoire critique de la découverte des longitudes (Avignon,1775). In addition, several of his papers are in Memoirés de mathématique et de physique rédigés à l’Observatoire de Marseille, 2 vols. (Avignon, 1755-1756).

Among the most important translations by Pezenas are C. Maclaurin’s Traité des fluxions, 2 vols. (Paris, 1749), and Éléments d’algèbre (Paris, 1750); J. T. Desaguliers’s Cours de physique expérimentale, 2 vols. (Paris, 1751); H, Baker’s Traité du microscope (Paris, 1754); John Ward’s Guide des jeunes mathématicines (Paris, 1756); J. Harrison’s Principes de la montre... (Avignon, 1767); R. Smith’s Cours complet d’optique, 2 vols. (Avignon, 1767); and W. Gardiner’s Tables de logarithmes (Avignon, 1770).

II. Secondary Literature. Besides the bibliographical articles cited above, the principal studies of Pezenas’s life and work are the following, listed chronologically: J. Lalande, “Éloge du P. Pezenas,” in Journal des scavans (1779), 569–571, repr. in Bibliographie astronomique (Paris, 1803), see index; J. B. Delambre, in Biographie universelle, XXXIII (1823), 563–565, also in new ed., XXXII (1861), 663–664; P. Levot, in F. Hoefer, ed., Nouvelle biographie générale, XXXIX (1862), cols. 791–792; and B. Aoust, in Mémoires de l’Académie des sciences, lettres et beaux-arts de Marseille, ser. 2, 20 (1870), 1-16. Details concerning various aspects of Pezenas’s work can be found in R. Taton, ed., Enseignement et diffusion des sciences en France au XVIIIe siècle (Paris, 1964), see index.

Juliette Taton