Gmelin ,.I. Johann Georg, a German naturalist, born in Tubingen, June 12,1709, died there, May 20, 1755. In 1731 he became professor of chemistry and natural history in St. Petersburg. In 1733 - '43 he made a scientific journey through Siberia. In 1747 he returned to Tubingen, and in 1749 was appointed professor of botany and chemistry there. His Reisen durch Sibirien (4 vols., Gottingen, 1751-'2) and Flora Sibirica (4 vols., St. Petersburg, 1749-70) are his principal works. II. Samuel Gottlieb, a German botanist, nephew of the preceding, born in Tubingen about 1744, died at Akhmetkent, in the Caucasus, July 27, 1774. He was professor of botany in St. Petersburg, and travelled extensively through southern Russia and the adjacent countries. While on his way from Derbend to Kisliar, he was seized and imprisoned by the khan of the Kaitak tribe, and died of privation and ill treatment. His chief works are Historia Fucorum (1768), and Reisen durch Russland zur Untersuchung der drei Naturreiche (4 vols., 1770-84), of which the concluding part is by Pallas. III. Johann Friedrich, nephew of Johann Georg, born in Tubingen, Aug. 8, 1748, died in Gottingen, Nov. 1, 1804. In 1771 he became professor of natural history and botany at Tubingen, and in 1778 professor of medicine and chemistry at Gottingen. He published, among other works, Onomatologia Botanica completa (10 vols., 1771-'8); Allgemeine Geschichte der rnineralischen Gifte (1777); Allgemeine Geschichte der Pflanzengifte (1777); and Geschichte der Chemie (3 vols., 1797-9). He was also the editor of the 13th edition of Linnaeus's Systema Naturoe. IV. Leopold, a German chemist, son of the preceding, born in Gottingen, Aug. 2, 1788, died in Heidelberg, April 13, 1853. He was educated at Gottingen, Tubingen, and Vienna, and from 1817 to 1851 was professor of medicine and chemistry at Heidelberg. In 1820 he made with Tiedemann a series of experiments on digestion, the result of which was published in his Die Verdauuug (2 vols., 1826-'7). His principal work is his Handbuch der theoretischen Chemie (3 vols., 1817-19; 5th ed., completed by Schloss-berger, List, and Liebig, 7 vols., 1853-'62). There is an English translation of this work, by Henry Watt (9 vols., London, 1848-'55).