Omalius D’halloy, Jean Baptiste Julien D

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(b. Liège, Belgium, 16 February 1783; d. Brussels, Belgium, 15 January 1875)


D’Omalius d’Halloy, who played a major role in the transition from the stratigraphic systems of Werner or Guettard to those of de la Beche and Murchison, was the only son of Jean Bernard d’Omalius d’Halloy, the son of an old and wealthy family, and Sophie de Thier de Skeuvre. Following his parents’ wishes, he was educated in the family tradition of law and public service. In 1801 he was sent to Paris, where they expected him to become acquainted with literature, art, and theater. But Paris was also the scientific center of Europe, and d’Omalius was attracted to the natural sciences. In 1803. over parental protests, he began serious scientific study, attending the lectures of Lacépède, the zoologist; Antoine de Fourcroy, the chemist; and Cuvier.

D’Omalius made his first geological tour in the Ardennes and Lorraine in 1804, In 1805-1806 he traveled throughout France, including the Belgian provinces, making the observations for his first important paper, “Essai sur la géologie du nord de la France” (1808), which established his scientific reputation. In this publication d’Omalius began, on the Continent, stratigraphic subdivision of the major Wernerian classes by superposition and paleontological criteria. This type of subdivision was later associated in England with the work of Bakewell and Smith and in America with that of Maclure and Eaton. The success of the essay led Coquebert de Montbret, head of the Bureau of Statistics of France, to engage d’Omalius to prepare a geological map of the Empire. This work was begun in 1809 and completed in 1813, but new administrative duties prevented d’Omalius from preparing the map for publication until 1823. In 1813 he presented to the Institut de France a “Mémoire sur I’etendue géographique du terrain des environs de Paris,” extending and significantly modifying the work on the Paris basin begun by Cuvier and Brongniart.

Political events ended the first period of d’Omalius’ scientific career. From 1813 to 1830, with his father’s urging, d’Omalius served in a succession of public offices: mayor of Brabant (1813); superintendent of Dinant (1814), then secretary general of Liáge; and governor of the province of Namur, Netherlands (1815-1830). A notable achievement of his administration was the Code administratif de la province de Namur (1827), on which he worked for several years. The establishment of Belgian independence in 1830 ended his governorship of Namur and allowed him to resume his scientific career. He never again entirely gave up science for public service, although in 1848 he was elected to the Belgian senate from Dinant, holding office until his death. From 1851 to 1870 he was vice-president of the senate.

In the first period of his scientific career, from 1804 to 1813, d’Omalius worked in stratigraphy and mineralogy. His Essai of 1808 opposed Wernerian geology by arguing that the inclination of strata is not due to deposition and that, in the same basin, inclined strata are older than horizontal strata. He also distinguished ten terrains among the strata of northern France. In his Observations sur un essai de carte géofogique de la France, des Pays-Bas et des contrées voisines (1823), d’Omalius brought the local descriptions of the geology of France into a uniform and sophisticated stratigraphic column, one that, in conjunction with the parallel efforts of Alexandre Brongniart, enjoyed wide acceptance and formed the basis for the development of Continental stratigraphy in the first half of the nineteenth century.

After returning to geology in 1830, d’Omalius was more speculative than in the earlier period. He also wrote about ethnology and defended the theory of evolution. His controversial views grew out of his conservative refusal to accept complete uniformitarianism in geology. In papers and in his textbook, Éléments de géologie (1831), d’Omalius argued that contemporary geological processes are not capable of having produced all formations. Reasoning from the traditional hypothesis that the earth was originally a hot mass cooling slowly, he insisted that the deepest structures—Werner’s primitive terrain, which he renamed plutonic terrain—had been formed by heat agencies no longer intensely active. Even in later epochs, when upper strata were formed by deposition in water, heat remained a secondary cause. Thus d’Omalius believed that many deposits of sand in Belgium had been ejected from the hot interior. These views, which he strongly defended in the 1840’s and 1850’s, when uniformitarianism was being accepted by the scientific community, were d’Omalius’ resolution of the contest between Werner’s and Hutton’s thories, which influenced his early career. In 1833, with the aim of completing an introduction to the science that he called “inorganic natural history,“ he published a 900-page tome on astronomy, meteorology, and mineralogy, the Introduction à la géologie.

While d’Omalius nominally eschewed hypotheses, he early adopted the catastrophic idea of craters of elevation, and he was one of the first to accept glacial concepts. D’Omalius was, in 1831, an early defender of the theory of organic evolution, rejecting Cuvier’s theory of successive creations as a “purely gratuitous hypothesis” (Elements de geolgie, pp. 526–527). He believed that species are not absolutely fixed, but change in response to changes in environment. Domestication, in which man alters species by controlling nutrition, for instance, is strong analogical evidence for similar processes in nature. While he rejected the notion that man had developed from a polyp, he did believe that the human species had evolved to some extent, suggesting that if man had existed at the beginning of the coal age, then at that time he must have possessed lungs permitting him to live in an atmosphere with more carbon dioxide than his lungs now allow. Contemporary man’s racial differentiation similarly resulted from changes in environment.

In his later years d’Omalius was reluctant to accept Charles Darwin’s theory of the origin of species. He agreed that natural selection occurs and alters species to a small degree, but he did not think natural selection is powerful enough to explain the major developments in paleontological series. He continued to believe that only environmental changes were sufficient to make major alterations in species.

D’Omalius’ evolutionary views were undoubtedly inspired by Lamarck and Geoffroy St.-Hilaire, whose famous debate with Cuvier over evolution had occurred in 1830, but they also derived from a fundamental belief in vital forces. D’Omalius thought that the hypothesis of physical-chemical forces was unable to explain living phenomena; rather, he believed that “each form of living being is determined by a special force” (“;Quatrieme note sur les forces naturelles,” in Bulletin de l’Académic royale des sciences… de Belgique, 32 [1871], 48–49). He conceived of the vital forces as analogous to the director of an industrial plant who oversees the assembly of a product according to his design. The vital forces thus directed organic responses to environmental change, thereby making evolution possible. This concept of vital force was compatible with the concept of an immortal soul—a matter of importance to d’Omalius, who was a practicing Catholic.

D’Omalius d’Halloy was a member of the Royal Academy of Sciences, Letters, and Fine Arts of Belgium and a foreign member of the Academy of Sciences (Paris).


I. Original Works. Most of d’Omalius’ articles were published in the Journal des mines and the Annales des mines, its successor; and the Bulletin and mémoires of the Royal Academy of Sciences, Letters, and Fine Arts of Belgium. Scattered pieces of correspondence are listed in the Catalogue genéralé des manuserits des hihliotheques publiques en France,48, 55; and “Paris: Tome II,” passim.

His most important works are “Essai sur la géologie du nord de la France,” in Journal des mines, 24 (1808), 123 158, 271–318, 345–392, 439–466; “Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines,” in Annales des mines, 7 (1823), 353–376; Éléments de géologie (Paris, 1831); Introduction à la géologie on première partie des éléments d’histoire naturelle inorganique, comprenant des notions d’astronomie, de météorologie et de mineralogie (Paris, 1833); and Coup d’oeil sur la géologie de la Belgique (Brussels, 1842).

II. Secondary Literature. The best biographical memoir is J. Guequier, “Omalius d’Halloy,” in Biographie nationale … de Belgique16 (1901), 157–166, with partial bibliography. There is a detailed biography by Jules Gosselet, in Bulletin de la Société géologique de France6 (1878), 453–467, which succeeds the major study by E. Dupont, “Notice sur la vie et les travaux de J. B. J. d’Omalius d’Halloy,” in Annuaire de l’Academie royale de Belgique, 42 (1876), 181-296, with a complete bibliography.

Ronald C. Tobey

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Omalius D’halloy, Jean Baptiste Julien D

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