(b. Paris, France, 5 September 1787; d. Paris, 9 December 1850)
Educated at the École Polytechnique and the École Normal Supérieurein Paris, Beudant began his career as répétiteur at the latter institution, leaving this post to become professor of mathematics at Avignon (1811) and then professor of physics at Marseilles (1813). During these years his primary interests were zoology and paleontology, tastes he acquired while studying with Gilet de Laumont. He studied species of coelenterates and mollusks, trying to determine whether freshwater varieties could adapt to saltwater and whether marine forms could have originated from freshwater fauna. Some of his observations were included in “Mémoire sur la possibilité de faire vivre des mollusques fluviatiles dans les eaux salées et des mollusques marins dans les eaux douces…”
Louis XVIII appointed Beudant as assistant director of his cabinet of mineralogy in 1814, charging him with the task of cataloguing the enormous mineralogical collection of the Comte de Bournon, which was to be moved to Paris from England the following year. This work directed Beudant’s attention from natural history to mineralogy and geology, with which he was thereafter concerned. In 1818 he was sent by the state on a scientific expedition to Hungary, where he gathered masses of important data that were published in his three-volume Voyage minéralogique et geólogique en Hongrie (1822).
In 1820 Beudant became professor of mineralogy and physics on the Faculty of Sciences at the Sorbonne but resigned the chair of physics so that Ampàre might have it. In 1839 he left the university and became inspecteur général des études, which was equivalent to being supervisor for the entire French educational system. He held this position until his death. In 1841 he wrote a grammar of the French language that was favorably received by his contem-poraries.
Mineralogical investigations, particularly experiments with carbonates and other salts, revealed to Beudant a principle of the combination of mineral substances that he expressed in Beudant’s law. Essentially, he found that some compounds dissolved in the same solution would precipitate together, forming a crystal whose properties they determined in common. The interfacial angles of this new crystal would have a value intermediate between the angles of the original compounds, proportional to the quantity of each. The same idea had been put forth by Robert Boyle in “The Origine of Form and Qualities” (1666). Beudant was rather conservative about the generality of his proposition, although Delafosse enthusiastically maintained that it should apply to all crystals.
The generalization of this idea, the law of isomorphism, was proposed by Mitscherlich in 1819.
I. Original Works. Beudant published a great number of papers in geology, mineralogy, zoology, and paleontology. The most important are “Mémoire sur la possibilité de faire vivre des mollusques marins dans les eaux salées et des mollusques marins dans les caux douces, considérée sous le rapport de la géologie,” in Journal de physique, 83 (1816), 268–284, and “Recherches sur les causes qui déterminent les variations des formes cristallines d’une même substance minérale,” in Annales de chimie, 8 (1818), 5–52. Among his texts are Voyage minéralogique et géologique en Hongrie pendant l’année 1818. 3 vols. (Paris, 1822); Traité élémentaire de minéralogie (Paris, 1824); Traité éléemenlaire de physique (Paris, 1824); Nouveaux éléments de grammaire française (Paris, 1841); and Cours élémentaire de minéralogie et de géologie (Paris, 1842).
II. Secondary Literature. Articles on Beudant are in Dictionnaire de biographie française, V (1951). 358–359, and Larousse grande dictionnaire du XIX siècle, III (Paris, 1867), 656.
Martha B. Kendall