PRéVOST, LOUIS-CONSTANT

(b.. Paris, France, 4 June 1787; d. Parts, 16 August 1856)

geology.

After deciding against a career in law, his stepfather’s profession, Prévost studied medicine but under the influence of Cuvier and Brongniart turned to geology. During a residence in Austria he studied the Tertiary strata of the Vienna basin; and in 1820, following his return to a teaching post at the Paris Athenée, he showed that these strata were much younger than those of the Paris basin and were thus more closely related to the present condition of the earth’s surface. In 1823-1824 he collaborated with Lyell in comparing the Tertiary and “Secondary” strata on both sides of the English Channel. As early as 1809 Prévost had been skeptical of Cuvier’s and Brongniart’s interpretation of the Parisian strata. In 1827 he argued that the strata with marine and freshwater fossils did not alternate in the succession but were lateral equivalents and therefore did not prove that periodic incursions of the sea had occurred over the continent. Prévost argued instead that all the strata had been formed within a single saltwater gulf analogous to the present English Channel, the freshwater fossils being present because of the outflow of large rivers similar to the present Seine. This work emphasized the importance of interpretations based on analogy with present conditions and thus made Prévost a supporter of Lyell’s, whose Principles he later intended to translate.

In 1830 Prévost was one of the founders of the Société Géologique de France (serving as president in 1834, 1839, and 1851); and in 1831 he was appointed, w th Cuvier’s support, to a new chair of geology at the Sorbonne. In the same year he accompanied an official expedition to study a new volcanic island off Sicily. Returning through Italy, he became convinced, like Lyell, that volcanoes are formed solely by the accumulation of ejected material and not, as Leopold von Buch and his followers maintained, by elevation from below. His views on both sedimentation and vulcanism placed him in an unorthodox position, especially within French geology. He opposed the paroxysmal dynamics of Cuvier and later of Élie de Beaumont, emphasizing instead the efficacy of “actual causes.” But he also questioned the validity of d’Orbigny’s use of fossils simply as indices of geological age, stressing instead their importance as indicators of ecological conditions that might have recurred at many periods. Yet despite this Lyellian approach, Prévost was explicitly influenced at the theoretical level by Deluc. Seeing geological history as a process of gradual withdrawal of the sea from the present continents, Prévost rejected the idea that powerful forces within the earth were capable of producing substantial elevation. Prévost was elected to the Academic des Sciences in 1848, having been an unsuccessful candidate in 1835 for the place vacated at Cuvier’s death.

BIBLIOGRAPHY

I. Original Works. Prévost’s principal publications are “Sur la constitution physique et géognostique du bassin à l’ouverture duquel est située la ville de Vienne en Autriche,” in Journal de physique, de chimie, et d’histoire naturelle, 91 (1820), 347-364, 460-473; “De l’importance de l’étude des corps organisés vivants pour la géologie positive … ,” in Mémoires de la Société d’histoire naturelle de Paris, 1 (1824), 259-268; “Observations sur lesschistes oolithiques de Stonesfield en Angleterre, et sur les ossements de mammifère qu’ils renferment,” in Annales des sciences naturelles, 4 (1825), 389-417; “Les continents actuels, ont-ils été, a plusieurs reprises, submergés par la mer?” in Mémoires de la Societé d’histoire naturelle de Paris, 4 (1828), 249-346;’’Notes sur l’île Julia, pour servir à l’histoire de la formation des montagnes volcaniques,” in Mémoires de la Société Géologique de France, 2 (1835), 91-124; “Essai sur la formation des terrains des environs de Paris,” in Académie des sciences. Section de géologie et minéralogie, Candidature de M. Constant Prévost (Paris, 1835), 93 124, which includes “Les continents actuels” and later notes and a valuable autobiographical summary of his work; “Sur la théorie des soulèvements,” in Bulletin de la Société Géologique de France, 11 (1840), 183-203; and “Sur la chronologic des terrains et le synehronisme des formations,” ibid.. 2nd sen, 2 (1845), 366-373.

II. Secondary Literature. A brief account of Prévost’s life and work is given in Hoefer, ed., Nouvelle biographie générale, XLI (Paris, 1862), 15-17.

M. J. S. Rudwick