MOBIUS, AUGUST FERDINAND Ger man astronomer and mathematician, was born at Schulpforta on Nov. 17, 179o. At Leipzig, Gottingen and Halle he studied for four years, and in 1815 became professor of astronomy at Leip zig, being chosen director of the university observatory, which was erected (1818-1821) under his superintendence. He died on Sept. 26, 1868. His doctor's dissertation, De computandis occultationibus fixarum per planetas (Leipzig, 1815), established his reputation as a theoretical astronomer. Die Hauptsdtze der Astronomie (1836), Die Elemente der Mechanik des Himmels (1843), may be noted amongst his other purely astronomical publications. His labours in pure mathematics appear for the most part in Crelle's Journal from 1828 to 1858. These papers are chiefly geometrical, many of them being developments and applications of the methods laid down in his great work, Der barycentrische Calcul (Leipzig, 1827), which, as the name im plies, is based upon the properties of the mean point or centre of mass. (See ALGEBRA : Universal.) This work abounds in sug
gestions and foreshadowings of some of the most striking dis coveries in more recent times—such, for example, as are con tained in H. Grassmann's Ausdehnungslehre and Sir W. R. Hamil ton's Quaternions. Mobius was a leader in the introduction of the powerful methods of modern projective geometry.
His Gesammelten Werke were published at Leipzig, (4 vols., 1885 1887).
(2) Theodor, son of the last-named, Scandinavian authority, born at Leipzig, June 22, 182 I . Among many papers and writings, his Catalogas librorum islandicorum et Norvegicorum aetatis mediae (1856) and V erzeichnis der auf dem Gebiet der altnordi schen Sprache and Literatur 1855 bis 1879 erschienenen Schrif ten (188o) as keys to Scandinavian bibliography, and his Edda Ausgabe as a text-book, are perhaps the most valuable to students. He died in Leipzig, April 25, 189o.