Lecornu, Léon François Alfred

(b. Caen, France, 13 January 1854; d. St. -Aubin-sur-Mer, Calvados, France 13 November 1940)

mechanics, mechanical engineering.

Lecornu proved an exceptional student at the secondary school in Caen; in his final year he won the prize of honor in the annual concours général and easily passed the competitive entrance examinations for both the École Normale Supérieure and the École Polytechnique. He entered the latter in 1872 but two years later transferred to the école Superérieure des Mines and began to pursue two careers simultaneously—one professional, the other academic.

His first engineering assignments were in Rennes and in Caen. In 1893, when he returned to Paris, he was promoted to chief engineer in charge of the technical supervision of the railroads of western France. He rose in the Corps des Mines to the rank of inspector general first class and retired in 1924.

In 1880 Lecornu received a doctorat és sciences from the Sorbonne with his dissertation, “Sur l’équilibre des surfaces flexibles et inextensible.” In 1881 he joined the faculty of Caen as associate professor. After his move to Paris he was appointed répétiteur at the école Polytechnique (1896) and professor of mechanics at the école des Mines (1900) and at the école Poly Technique (1904). After retiring from the latter in 1927, he continued to teach at the école Nationale Supérieure d’Aéronautique until 1934

The tenor of Lecornu’s original work in mechanics is the application of the classical methods to the analysis of a variety of engineering problems. In his dissertation he established the relationship between the stresses and the geometrical characteristics of deformed surfaces. Applying his general theory to an ellipsoidal surface, he was able to determine the conditions of rupture of air balloons. A similar approach was used to analyze the stability of rotating millstones. Other representative studies are his papers on pendulums of variable length, on inertial errors in the steam engine indicator, on speed regulation, and on the dynamics of gear teeth.

Much of Lecornu’s writing was expository and didactic and was characterized by an informal, popular style. He wrote a number of textbooks on mechanics and mechanical engineering, and edited the multivolume Enctclopédie de mécanique appliqucée (Paris, 1924). In 1910 Lecornu was elected a member of the mechanics section of the Académie des Sciences, which he served as president in 1930. He received the Prix Ponce let (1900) and the Prix Montyon (1909), and was a commander of the Legion of Honor.

Lecornu also had two minor avocations: geology (he published extensively while a mining engineer in Normandy) and the piano.

BIBLIOGRAPHY

I. Original Works. Lecornu’s books are Régularisation du mouvement dans les machines (Paris, 1898); Les régulateurs des machines a vapeur (Paris, 1904); Dynamique appliquée (paris,1908); Théorie des moteurs legers (Paris, 1911); Cours de mécanique, professé á l’ école Polytechnique, 3vols. (Paris, 1914—1918);La mécanique: les idées et les faits (Paris, 1918); Théorie mécanique de l’ élasticité (Paris,1929); and propriétés générales des machines(Paris, 1930). Incomplete bibliographies of his scientific papers are given in Poggendorff, Iv , 855; V , 721; and VI , 1485; and in Royal Society Catalogue of Scientific papers, X , 544-545; and XVI , 664-655.

II. Secondary Literature. The principal source on Lecornu is the obituary by H. Vincent, in Comptes rendus hebdomadaires des séances de l’ Académie des sciences, 211 (1940), 493-498. Additional facts and a portrait are in N. Imbert, ed., Dictionnaire national des contemporains, I (Paris, 1936),378. The catalog of the Bibliothéque Nationale lists also a Notice sur les travaux scientifiques de M. Léon Lecornu (Paris, 1896).

Otto Mayr