JACOBI, KARL GUSTAV JACOB (1804–1851), German mathematician, brother of Moritz Hermann *Jacobi. Born in Potsdam, he was a child prodigy. He studied philosophy, philology, and mathematics at the University of Berlin, and in 1825 became a lecturer in mathematics. He and his brother converted to Christianity in order to remove any possible bar to government posts. His career was also helped by the famous mathematician Friedrich Gauss. A brilliant teacher, Jacobi was invited to Koenigsberg, where he became a professor at the age of 23. Overwork, together with financial difficulties caused by his father's death, brought him to a state of near collapse requiring a long convalescence. Jacobi met Sir William Rowan Hamilton, the great Irish mathematician, and, as a result of this meeting, he continued Hamilton's work in the field of dynamics. After a short and unhappy involvement in politics which cost him his royal grant, he returned to his original work. On the recommendation of Baron Alexander von Humboldt, the German naturalist, the grant was again awarded him. By 1849 Jacobi was the leading mathematician in Europe after Gauss. He died in Berlin of smallpox. Jacobi's works on differential equations and the calculus of variations serve as the mathematical basis for modern physics. His collected works, Gesammelte Werke, were published by the University of Berlin in eight volumes (1881–91).
L. Koenigsberger, Karl Gustav Jacob Jacobi (Ger., 1904); E.T. Bell, Men of Mathematics (1937), index.