Deluc I. Jean Andre, a Swiss physicist, born in Geneva, Feb. 8, 1727, died at Windsor, England, Nov. 7, 1817. He received an excellent education, and spent the first half of his life in commercial pursuits. During his numerous journeys of business he made, with the assistance of his brother Guillaume An-toine, a fine collection of objects of natural history. About 1773, obliged by commercial misfortune to leave his native city, he went to England, was elected a fellow of the royal society of London, and was appointed reader to the queen, which situation he held till his death. In the latter part of his life he made several tours in central Europe, passing six years in Germany, and after his return in 1806 made a geological tour in England. He received at Gottingen the appointment of honorary professor of geology. His principal writings treat of geology and meteorology; his first important work was Recherches sur les modifications de l'atmosphere (2 vols. 8vo, Geneva, 1772), which contains many valuable suggestions on the practical applications of barometers, thermometers, and hygrometers. He substituted mercury for spirits of wine in Reaumur's thermometer, and invented a portable barometer, establishing correct rules for determining by this instrument the height of mountains and the depth of mines.

Other papers on subjects connected with meteorology are scattered through the "Philosophical Transactions" from 1771 to 1792. Religious fervor is manifest in all his works, contrasting strikingly with the prevailing spirit of the age. His Let-tres physiques et morales sur l'histoire de la terre (6 vols. 8vo, the Hague, 1778-'80) treat particularly of the comparatively recent origin of the present continents and their mountains, and the difficulty of carrying back this origin to a period more remote than that assigned by the Mosaic chronology to the flood. His reverence for the Bible led him to attempt to explain all apparent contradictions between geological phenomena and the Mosaic account of creation. Though his conclusions are not now admitted in geology, he extended the limits of this science. In his " Elementary Treatise on Geology" (8vo, London, 1809), he opposes the system of Hutton and Playfair, which attributes the changes in the earth's structure to the action of fire. Cuvier ranks him among the first geologists of his age.

He contributed many papers to the Journal de Physique, the Journal des Mines, and the "Philosophical Magazine." He separated the chemical from the electrical effects of the voltaic pile, and constructed an ingenious but incomplete instrument, the dry electric column, for measuring the electricity of the air. He published also several volumes of his geological travels in England and northern and central Europe, and works on the Baconian philosophy, on the religious education of children, and on Christianity. II. Guillanme Antoinc, brother of the preceding, born in 1729, died in Geneva, Jan. 26, 1812. He travelled extensively, and at Vesuvius and Etna in 1756-7 made fine collections of volcanic products, fossil shells, and other objects of natural history. His papers on mineralogy and geology may be found in the Journal de Physique, 1798-1804; Bibli-otheque Britannique, 1801; and Mercure de France, 1806-7.