Benoit, Justin-Mirande René

(b. Montpellier, France, 28 November 1844; d. Dijon, France, 5 May 1922)

physics.

As director of the Bureau International des Poids et Mesures from 1889 to 1915, René Benoit played a large role in standardizing units of length, temperature, and electrical resistance for the scientific world.

Benoit’s early training was in medicine, in compliance with the wishes of his father, Justin Benoit, a distinguished surgeon and dean of the faculty at the medical school of Montpellier. No sooner had René received his medical doctorate (1869), however, than he turned to his first interest, physics, and entered the laboratory of the École des Hautes Études. Here he conducted a series of experiments on the temperature dependence of electrical resistance in metals and received his doctoral ès sciences in 1873. Four years of work in the electrical industry followed, after which the Bureau International des Poids et Mesures offered him an assistant directorship.

The bureau was hardly three years old when Benoit arrived, and its main concern was the preparation of prototype standard units for its member nations. The new appointee was charged with determining the best method of measuring lengths. This involved a detailed study of thermal expansion, the various devices for measuring dilation, and the relative merits of different thermometers. Once the standard lengths were set up, Benoit played a large role in their verification and in establishing their relation to other standard units, such as the English yard.

The distribution of the first set of prototype lengths in 1889 coincided with Benoit’s appointment us director of the bureau. In this capacity he became deeply involved in research to determine the relationship between the standard meter and various wavelengths of light, work that was carried out primarily by A. A. Michelson in 1891 and by C. Fabry and A. Perot in 1906. He was also associated with the standardization of twenty-four-meter Jaderin surveying wires and with the determination of the standard ohm.

Along with the directorship of the bureau, Benoit held the honorary position of president of the Société Française de Physique, correspondent of the Académie des Sciences, honorary fellow of the Physical Society of London, and officer of the Legion of Honor. On his retirement in 1915, due to failing health and eyesight, his colleagues at the bureau made him honorary director as a token of their esteem.

BIBLIOGRAPHY

1. Original Works. Benoit’s published works are cataloged in Poggendorff, III, 107; IV, 98; V, 93; VI,278; and in the Royal Society Catalogue of Scientific Papers, VII, 139; IX, 191; XIII, 449.

His thesis for his doctorat ès sciences is Études expérimentales sur la résistance électrique des métaux et sa variation saus l’influence de la température (Paris, 1873), Devices for measuring dilation are discussed in “Mesures de dilation et comparaison des règles métriques,” in Mémories et travaux di Bureau international des poids et mesures, 2 (1883), C.1–C.174, C.i–C.clxvii; and 3 M1884). C.1–C.44, C.1- C.i–C.xlvi. Benoit’s work in determining the standard ohm is presented in Détermination de l’ohm (Paris, 1884), written with E.E. N. Mascart and F.G. Nerville; and Construction d’étalons prototypes de résistance électrique(Paris, 1885). An account of the relative merits of different thermometers is “Études préliminaires sure les thermomètres...,” in mémories et travaux du Bureau international des poids et mesures, 7 (1890), 10-13. Research on the relationship between the standard meter and various wavelengths of light is presented in “Nouveles déterminations de mètre en longueurs d’ondes lumineuses,” in Comptes rendus de l’Académie des sciences, 144 (1907), 1082. For an idea of his work as director of the bureau, see his “Rapports règlementaires du directeu du Bureau international des poids et mesures,” Procès-verbaux des séances du Comité international des poids et mesures, in each volume from 1890 to 1915.

II. Secondary Literature; The most complete biography of Benoit is Charles Édourd Guillaume, in Procès-verbaux des séances du Comité international des poids et mesures, 20 ; (1923). For shorter works, see Nature, 109 (1922), 820; and Dictionnaire de biographie française, V, 1442.

Eugene Frankel