MICHEL-LéVY, AUGUSTE

(b. Paris, France, 7 August 1844; d. Paris, 27 September 1911)

geology, mineralogy.

The greater part of Michel-Lévy’s scientific work was accomplished in collaboration with Ferdinand Fouqué. Jointly they introduced into France the study of rocks by microscopical petrography and artificially synthesized many igneous rocks in order to determine the conditions necessary for the production of their mineral constituents. In addition Michel-Lévy, working with feldspars, founded the method of statistical research on the constituents of rocks. He was the first to demonstrate the importance of birefringence in petrographic studies, and he determined this optical constant for a large number of minerals. In the field Michel-L7eacute;vy devoted twenty years to the study of the eastern part of the Massif Central, of the Morvan Massif, and of the western Alps.

Michel-Lévy’s father was a noted military hygienist and president of the Académic de Médecine. Independently wealthy, Michel-Lévy was raised in an intellectual atmosphere devoted to both science and literature. As a result he won numerous prizes in the general concours from 1859 to 1861 and entered the école Polytechnique in 1862. He ranked first there and at the école des Mines, from which he graduated in 1867. Michel-Lévy entered the service of the Carte Géologique in 1870 and was its director from 1887 until his death. In 1879 he was appointed engineer of mines of the first class; he became chief engineer of this division in 1883; and he attained the highest rank, inspector general in 1907. He was elected to the Académic des Sciences in 1896. In addition Michel-Lévy was a member of the administrative council of the Conservatoire National des Arts et Métiers, of the national council of hygiene of France, and of the council of public hygiene for the department of the Seine.

Together with Fouqué and Alfred Lacroix, Michel-Lévy pioneered the science of microscopical petrography in France. His two-volume work, Minéralogie micrographiqueé: Roches éruptices françaises (1879), written with Fouqué, demonstrated the results of this method to French scientists. In it they also employed a new classificatory system for volcanic rocks, using as criteria mineralogical composition, structure, and chemical composition. In 1880, with Lacroix, Michel-Lévy published Tableaux des minéraux des roches; and in 1889 they produced Les minéraux des roches which described the optical and chemical methods of studying minerals in thin sections and the microscopical features of rock-forming minerals. Michel-Lévy’s Étude sur la determination des feldspaths dans les plaques minces (1894) was a significant contribution to the microscopic study of feldspars in thin sections.

From 1878 to 1882 Michel-Lévy and Fouqué worked to synthesize igneous rocks artificially, believing that if they could determine the peculiar conditions surrounding the rocks’ genesis, they might arrive at important geological conclusions. Despite the meager equipment of the laboratory at the Collège de France in which they carried out their experiments, they produced rocks having the mineralogical composition and structure identical with most of the volcanic rocks found in nature. They published jointly twenty-two articles and a book, Synthèse des minéraux et des roches (1882), which incorporated the results of their work. Their most important conclusions were that the degree of crystallinity depended largely upon the rate of cooling and that rocks of distinctly different mineralogical compositions would be formed from the same magma, depending upon the conditions of crystallization. Their failure to reproduce the trachytes and rhyolites demonstrated that in order to obtain the characteristic elements of these rocks, the presence of mineralizers was necessary to lessen the viscosity of the magma and to allow crystallization.

The principal result of Michel-Lévy’s fieldwork in geology was in distinguishing the two successive phases of folding and dislocation of the Massif Central toward the end of the late Paleozoic. His analysis of the dislocations superimposed on the eastern portion of the Massif Central caused him to trace them to the east and to search for their influence on the tectonic movements and volcanic phenomena of the Tertiary. In conjunction with this research he mapped Clermont-Ferrand, studied the lavas of the neighboring regions, and explored and mapped portions of the western Alps.

BIBLIOGRAPHY

Michel-Lévy’s chief publications treating the application of optical methods to the study of minerals in thin sections are Minéralogie micrographique: Roches éruptives françaises 2 vols. (Paris, 1879), written with F. Fouqué Tableaux des minéraux des roches (Paris, 1880), written with A. Lacroix; Les minéraux des roches (Paris, 1889), written with A. Lacroix; and Étude sur la détermination des feldspaths dans les plaques minces (Paris, 1894). In petrography he collaborated with F. Fouqué in Synthèse des minéraux et des roches (Paris, 1882) and also published Structures et classifications des roches éruptives (Paris, 1889). In addition he published either alone or jointly some 150 articles on geological or mineralogical subjects, and he contributed 10 maps to the Carte Géologique.

A biography is Alfred Lacroix, Notice historique sur Auguste Michel-Lévy (Paris, 1914), which includes a complete bibliography.

John G. Burke