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D'ALEMBERT, dalliebie, the assumed MUM of JEAN LE 'ROND French mathematician and philosopher: b. 1717; d. 1783. He was the natural son of Chevalier Destouches and Madame de Tencin. As an infant he was left on the portico of the chapel of Saint Jean le Rond. His father contributed secretly toward his support and had him educated by the Jan senists at the College Mazarin, where he was especially brilliant in mathematics, physics and astronomy. At the age of 22 he published a work on the integral calculus and two years later a work on the refraction of solid bodies. His (1743) is an epoch in mechani cal philosophy. In it is elaborated his famous principle, "The impressed forces are equivalent to the effective force.* He was elected to the Academy of Sciences in 1741 and to the French Academy in 1754, becoming the perpetual secre tary of the latter in 1772. From 1751 to 1758 he was associated with Diderot in editing the 'Encyclopedic.) To it he contributed the gen eral introduction, sketching in broad outline the evolution of civilization, art and science. He

was invited by Fredrick II to become presi dent of the Berlin Academy, and by Catharine II of Russia he was offered 100,000 francs a year as tutor to her son. Because of his desire to live simply, he refused both offers. In his lastyears he was closely associated with Mlle. de l'Espinasse, and her death in 1776 was a shock from which he never recovered. D'Alembert ranks among the greatest geometri cians of his century, and holds a high place also in literature and philosophy. His great service to letters was his exposure of the evils of patronage and his fostering the independence of his class from social and political power. Consult Bertrand, 'D'Alembert) (Paris 1889); Condorcet, (Eloge de D'Alembert) (delivered before the Academy, 1784); Tallentyre, "D'Alembert the Thinker,* in his 'Friends of Voltaire) (London 1906). There is a partial edition of D'Alembert's by Bossange (Paris 1821).