LAGRANGE, 1:1'griiNzW. .TosF.rn-Lorts (1736-1S12). The greatest French tician of the eighteenth century. Ile was born at Turin. his father being War Treasurer to the King of Sardinia. Lagrange was educated at the College of Turin. At first he became interested in speculative philosophy, but his extraordinary mathematical ability soon made it clear that the proper domain of his activity was mathematics. At nineteen he communicated to Euler his solu tion of the famous isoperimetrie problem, which had led him to establish the principles of the calculus of variations. The result was that Lagrange at once took a place among the fore most savants of Europe. He was soon wade pro fessor of mathematics in the artillery school at Turin, and in 175S he founded the society which subsequently became the Royal Academy of Turin. In 1764 he received the prize offered by the Academy of Sciences at Paris for an in vestigation on the libration of the moon; in 1766 he was likewise successful in a question concerning the theory of the satellites of J pi t yr, and in the same year was called to take Euler's place as director of the Academy of Ber lin, which position he occupied for twenty years. Ile then went to Paris, and became a member of the Academy. During the Revolution he was at the head of the commission which had in charge the establishment of the decimal system, and was also a member of the bureau for reward ing useful inventions. On the establishment of
the Evole Polyteehnique (1797) Lagrange was made professor there. After the Revolution he was made professor in the newly established Eeole No-male. Under Napoleon he was made a member of the Senate and given the rank of count. In pure mathematics Lagrange is noted for his contributions to the theory of series, the theory of numbers, differential equations, the numerical solution of equations, and the cal culus of variations. Ms astronomical work was, however, quite as remarkable. His most noted work is analytique (1788; 3d ed. 1853-55; German trans. by Servus, 1887). His other works are: Theorie des fonetions wady tiques, eontenant les prineipes du caleul diffe rentia (1797; 3d ed. 1847: German trans. IT arlison. ; Traits de la resolution des equations nuin('riques (1798; 3d. ed. 1826); LecOlIR .cur le eatenl des fouctions (180G) : Lec tures on Elonentary• Mathematics (trans. by McCormack, Chicago, 1898) ; besides a large number of memoirs. His complete works, in' fourteen volumes, were published at Paris in 1866-92. 11 is manuscripts were purchased in 1815 and given to the Institute by Carnot. La grange's name is connected with numerous inathe matieaI theorems. For his biography, consult Delambre, in Lagrange's' (Ent:7-es, vol. i. (Paris, 1866 )