D'Alembert
Collier's New Encyclopedia (1921)
JEAN LE ROND (dälon-bār'), a French mathematician and encyclopædist; born in Paris, Nov. 16, 1717; was the natural son of Madame de Tencin and the Chevalier Destouches; and was brought up by the wife of a poor glazier; but his father, without publicly acknowledging the paternity, secured to him an allowance of 1,200 francs a year. At 12 the boy entered the College Mazarin, where he soon showed his lifelong passion for mathematical studies. His first distinction was admission at 23 to the Academy of Sciences. Two years later appeared his "Treatise on Dynamics," which reduces all the laws of motion to the consideration of equilibrium, thereby marking an epoch in mechanical philosophy. Later works were: "General Cause of Winds," which gained the prize of the Academy of Berlin, 1746, and which contains the first conception and use of the Calculus of Partial Differences; "Equilibrium and movement Fluids" (1744); "Precession of the Equinoxes and Change of the Axis of the Earth" (1749); and "The Several Important Points in the System of the Works" (8 vols His "Mathematical World" (1754). vols. 1761-1780) contain an immense number of memoirs, some on new subjects, some containing developments of his previous works. D'Alembert did not confine himself to physical science. For the great "Encyclopédia" planned by Diderot he wrote the famous "Preliminary Discourse," a noble tribute to literature and philosophy. Besides numerous articles in the "Encyclopédia" (the mathematical portion of which he edited), he published books on philosophy, literary criticism, the theory of music, and a treatise "On the Destruction of the Jesuits" (1765), which involved him in controversy. He became secretary to the Academy in 1772, and thereafter he wrote the lives of all the members deceased between 1700 and that year-one of the most pleasing of his works. His literary works have been published by Bossange (5 vols., 1821). He died Oct. 29, 1783.
What Has Changed in the Last Century
The life Collier's set out in 1921 is still the life scholars tell: the foundling left at the church of Saint-Jean-le-Rond, the unacknowledged son of Mme de Tencin, the "Treatise on Dynamics" of 1743 and the "Preliminary Discourse" to Diderot's Encyclopédie. What has grown is his standing as a mathematician rather than as a man of letters: d'Alembert's principle remains a standard tool in mechanics courses, and his 1747 solution of the vibrating-string problem is now credited as the first general solution of a partial differential equation, the wave equation, whose operator carries his initial. A full critical edition of his complete works has been in progress in France since the late twentieth century, drawing on correspondence Collier's editors never saw. Otherwise the entry reads much as it did in 1921.
Written for this edition, 2026.