LAGRANGE, JOSEPH LOUIS French mathematician, was born at Turin, on Jan. 25, 1736.„ He was of French extraction, his great-grandfather, a cavalry captain, hav ing passed from the service of France to that of Sardinia, and settled in Turin under Emmanuel II.
Lagrange was educated at Turin college and his early tastes were more classical than scientific. His interest in mathematics was aroused by the chance reading of a memoir by Halley (Phil. Trans. xviii. p. 96o). He then began unaided a course of study pursued with such effect that at the age of 18 he was appointed professor of geometry at the artillery academy. During the fol lowing year he sent to Euler a method of dealing with the isoperi metrical problem out of which grew the calculus of variations. In 1758 Lagrange, aided by the marquis of Saluces and G. F. Cigna, founded the society which was later incorporated as the Turin Academy of Sciences. To the five volumes of its memoirs (Miscellanea Taurinensia) he contributed many papers.
By 1761 Lagrange was recognized as the greatest living mathe matician; but, owing to his intense application in the nine previ ous years, his health now broke down, and, although partially restored by rest, his nervous system was permanently impaired. In 1764 he was awarded the prize offered by the Paris Academy of Sciences for an essay on the libration of the moon, in which he uses his now well known equations. This success encouraged the academy to propose, in 1766, as a problem the theory of the Jovian system. The prize was again awarded to Lagrange ; and he won the same distinction in 1772, 1774 and 1778. He visited Paris and there met Clairaut, D'Alembert the Abbe Marie, and others. In 1776 Lagrange, on the recommendation of Euler and D'Alembert, went to Berlin to fill the post at the academy vacated by Euler; at the invitation by Frederick the Great who expressed the wish of "The greatest king in Europe" to have "the greatest mathematician in Europe" at his court. Lagrange lived in Berlin
for 20 years, during which time he communicated many memoirs to the Berlin academy dealing with algebra, mechanics and as tronomy, and produced his great work Mecanique analytique, which testifies to his genius for generalization and analysis. A publisher for this work was found by Legendre, in 1788, in Paris.
After the death of Frederick the Great, Lagrange accepted Louis XVI.'s invitation to Paris. Here he was given apartments in the Louvre, was continually honoured, and was treated with respect throughout the Revolution. In 1792 he married the daughter of the astronomer Lemonnier, and, although she was much younger than he, the union proved a very happy one. In 1793 he was made president of the commission for the reform of weights and measures, and in 1795 appointed professor in the Ecole Normale, Paris; the school, however, was closed after a few months. In 1797 he became a professor in the newly f ounded Ecole Polytechnique, and his lectures were as elegant and original as his writings. The same year he published Theorie des fonctions analytiques, which followed the lines of his lectures given on differential calculus. In 1810 he began the revision of his Mecanique analytique, but died on April to, 1813, before it was completed. He was buried in the Pantheon, the funeral oration being given by Laplace and Lacepecle. Lagrange was a very modest man, and had a great dislike of controversy.