OHM. I. Georg Simon, a German physicist, born in Erlangen, March 16, 1787, died in Munich, July 7, 1854. He was the son of a locksmith, and in his boyhood worked in his father's shop. He studied at Erlangen, taught mathematics in various places, and in 1817 was appointed professor in the Jesuit college in Cologne. In 1818 he published a work on the elements of geometry. He devoted himself particularly to the investigation of the laws governing galvanic currents, and by a combination of mathematical and experimental investigation, carried on for many years, he at length discovered and established the law which forms the basis of the mathematical theory of electricity. (See Galvanism.) His discoveries were first announced in 1825-'6 in scientific journals, and more completely in his Die galvanische Kette, mathematisch bearbeitet (Berlin, 1827; translated into English in Taylor's “Scientific Memoirs,” vol. xi., London, 1841). The fundamental theorem of his doctrine is known as “Ohm's law.” In 1826 he resigned his professorship, and was director of the polytechnic school in Nuremberg from 1833 to 1849, when he was appointed professor of physics at Munich. In 1841 the royal society of London conferred upon him the Copley medal. He also published Elemente der analytischen Geometrie (Nuremberg, 1849), Grundzüge der Physik (1854), and other works. II. Martin, a German mathematician, brother of the preceding, born in Erlangen, May 6, 1792, died in Berlin, April 1, 1872. He studied at the university of Berlin, and in 1817 was appointed professor of mathematics and physics in the gymnasium at Thorn. In 1821 he removed to Berlin, and in 1839 became a full professor in the university. He delivered courses of lectures at the academy of architecture from 1824 to 1831, and at the schools of artillery and engineering from 1833 to 1852; and he also taught in the military school from 1826 to 1849. He published Versuch eines vollkommen consequenten Systems der Mathematik (9 vols., Nuremberg, 1822-'52); Lehrbuch der Mechanik (3 vols., Berlin, 1836-'8); Geist der mathematischen Analysis (2 parts, 1842-'5; the first part translated into English by A. J. Ellis, London, 1843); and Die Dreieinigkeit der Kraft (Nuremberg, 1856).