Engraved by Robt. Hart.
LA GRANGE.
From a Bust in the Library of the
Institute of France.
Under the Superintendance of the Society for the Diffusion of Useful Knowledge.
London, Published by Charles Knight, Pall Mall East.
The father of Lagrange, luckily perhaps for the fame of his son, was ruined by some unfortunate speculation. The latter used to say, that had he possessed fortune, he should probably never have turned his attention to the science in which he excelled. He was placed at the College of Turin, and applied himself diligently and with enthusiasm to classical literature, showing no taste at first for mathematics. In about a year he began to attend to the geometry of the ancients. A memoir of Halley in the Philosophical Transactions, on the superiority of modern analysis, produced consequences of which the author little dreamed. Lagrange met with it, before his views upon the subject had settled: and immediately, being then only seventeen years old, applied himself to the study of the modern mathematics. Before this change in his studies, according to Delambre[[7]], after it, according to others, but certainly while very young, he was elected professor at the Royal School of Artillery at Turin. We may best convey some notion of his early proficiency, by stating without detail, that at the age of twenty-three we find him—the founder of an Academy of Sciences at Turin, whose volumes yield in interest to none, and owe that interest principally to his productions,—a member of the Academy of Sciences at Berlin, an honour obtained through the medium of Euler, who shortly after announced him to Frederic of Prussia as the fittest man in Europe to succeed himself,—and settling, finally, a most intricate question[[8]] of mathematics, which had given rise to long discussions between Euler and D’Alembert, then perhaps the two first mathematicians in Europe. He had previously extended the method of Euler for the solution of what are called isoperimetrical problems, and laid the foundation for the Calculus of Variations, the most decided advance, in our opinion, which any one has made since the death of Newton.
[7]. Éloge de Lagrange, Mémoires de l’Institut. 1812.
[8]. The admissibility of discontinuous functions into the integrals of partial differential equations.
In 1764 he gained the prize proposed by the Academy of Sciences for an Essay on the Libration of the Moon; and in 1766, that for an Essay on the Theory of the Satellites of Jupiter. In the former of these we find him, for the first time, using the principle of virtual velocities, which had hitherto remained almost a barren truth, but which he afterwards made, in conjunction with the principle known after the name of D’Alembert, the foundation of the whole of mechanical science.
In 1766, Euler, intending to return to St. Petersburg, resigned the situation which he held at the Court of Berlin, that of director of the physico-mathematical class of the Academy of Sciences. Frederic offered this place to D’Alembert, who refused it for himself, but joined with Euler in recommending Lagrange. The King of Prussia acceded to their suggestion, and Lagrange was invited to establish himself at Berlin, with a salary equivalent to 6,000 francs.
Lagrange remained at Berlin till after the death of Frederic. He here married a lady who was related to him, and who came from Turin at his request. She died after a lingering illness of several years, marked by the most unceasing attention on the part of her husband, who abandoned his pursuits to devote himself entirely to her during her illness. Nevertheless the period of his sojourn at Berlin is perhaps the brightest of a life, most years of which, from the age of eighteen to that of seventy, were sufficient to ensure a lasting reputation. He here laid the foundation of his Theory of Functions, of his general method for determining the secular variations of the planetary orbits; and here he wrote his Mécanique Analytique.
At the death of Frederic, he found that science was no longer treated with the same respect at the Court of Berlin. He had found from the commencement of his stay there, that foreigners were looked upon with dislike, and his spirits had not recovered the loss of his wife. Many advantageous offers were made to him by different courts, and among the rest by that of France. Mirabeau, who was then at Berlin, first pointed out to the ministers of Louis XVI. the acquisition which was in their power. Lagrange removed to Paris in 1787, and remained there till his death.
He was then weary of his pursuits, and it is said that his Mécanique Analytique, which he had sent from Berlin to be printed in Paris, lay unopened by himself for more than two years after its publication in 1788. He employed himself in the study of ecclesiastical and other history, of medicine, botany, and metaphysics. When the discoveries of the chemists changed the theory and notation of their science, or rather created a science where none existed before, he threw himself upon the new study with avidity, and declared that they had made it easy; as easy as algebra.
In 1792, being then fifty-six years of age, he married Mlle. Lemonnier, daughter of the astronomer of that name, and daughter, grand-daughter, and niece of members of the Academy of Sciences. This lady well deserves honourable mention in every memoir of Lagrange, for the affectionate care which she took of his declining years.