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ALEMBERT, JEAN LE ROND

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Originally appearing in Volume V01, Page 540 of the 1911 Encyclopedia Britannica.
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ALEMBERT, See also:JEAN LE ROND D' (1717—1783), See also:French mathe- matician and philosopher, was See also:born at See also:Paris in See also:November 1717. He was a foundling, having been exposed near the See also:church of St Jean le Rond, Paris, where he was discovered on the 17th of November. It afterwards became known that he was the illegitimate son of the See also:chevalier See also:Destouches and Madame de See also:Tencin. The See also:infant was entrusted to the wife of a glazier named See also:Rousseau who lived See also:close by. He was called Jean le Rond from the church near which he was found; the surname Alembert was added by himself at a later See also:period. His See also:father,, without disclosing himself, having settled an See also:annuity on him, he was sent at four years of See also:age to a boarding-school. In 1730 he entered the See also:Mazarin See also:College under the Jansenists, who soon perceived Lis exceptional See also:talent, and, prompted perhaps by a commentary on the See also:Epistle to the See also:Romans which he produced in the first See also:year of his philosophical course, sought to See also:direct it to See also:theology. His knowledge of the higher See also:mathematics was acquired by his own unaided efforts after he had See also:left the college. This fact naturally led to his crediting himself with many discoveries which he after- wards found had been already established, often by more direct and elegant processes than his own. ALEMBERT 539 On leaving college he returned to the See also:house of his See also:foster-See also:mother, where he continued to live for See also:thirty years. Having studied See also:law, he was admitted as an See also:advocate in 1738, but did not enter upon practice. He next devoted himself to See also:medicine, but his natural inclination proved too strong for him, and within a year he resolved to give his whole See also:time to mathematics.

In 1741 he received his first public distinction in being admitted a member of the See also:

Academy of Sciences, to which he had previously presented several papers, including a Memoire sur le calcul integral. (1739). In his Memoire sur le See also:refraction See also:des See also:corps solides (1741) he was the first to give a theoretical explanation of the phenomenon which is witnessed when a See also:body passes from one fluid to another more dense in a direction not perpendicular to the See also:surface which separates the two fluids. In 1743 he published his Traite de dynamique, a See also:work famous as developing the See also:mechanical principle, known as "Alembert's Principle," first enunciated in 1742 (see See also:MECHANICS). In 1744 Alembert applied this principle to the theory of the See also:equilibrium and the See also:motion of fluids (Traite de l'equilibre et du mouvement des fluides), and all the problems before solved by geometricians became in some measure its corollaries. This See also:discovery was followed by that of the calculus of partial See also:differences, the first trials of which were published in his Reftexion sur la cause generale des vents (1747). This work was crowned by the Academy of See also:Berlin, and was dedicated to See also:Frederick the See also:Great, who made several unsuccessful attempts to induce him to See also:settle in Berlin. In 1763 he visited Berlin, and on that occasion finally refused the See also:office of See also:president of the Academy of Berlin, which had been already offered to him more than once. In 1747 he applied his new calculus to the problem of vibrating chords, the See also:solution of which, as well as the theory of the oscillation of the See also:air and the See also:propagation of See also:sound, had been given but in-completely by the geometricians who preceded him. In 1749 he furnished a method of applying his principles to the motion of any body of a given figure; and in 1754 he solved the problem of the precession of the equinoxes, determined its quantity and explained the phenomenon of the See also:nutation of the See also:earth's See also:axis. In 1752 he published an Essai d'une nouvelle theorie sur la resistance des fluides,which contains a large number of See also:original ideas and new observations: In 1746 and 1748 he published in the See also:Memoirs of the Academy of Berlin " Recherches sur le calcul integral," a See also:branch of mathematical See also:science which is greatly indebted to him. In his Recherches sur diferents points importants du systeme du monde (1754—1756) he perfected the solution of the problem of the perturbations of the See also:planets, which he had presented to the academy some years before.

Alembert's association with See also:

Diderot in the preparation of the Dictionnaire Encyclopedique led him to take a somewhat wider range than that to which he had previously confined himself. He wrote for that work the Discours preliminaire on the rise, progress and See also:affinities of the various sciences, which he read to the French Academy on the See also:day of his See also:admission as a member, the 18th of See also:December 1754. He also wrote several See also:literary articles for the first two volumes of the See also:Encyclopaedia, and to the remaining volumes he contributed mathematical articles chiefly. One of the few exceptions was the See also:article on " See also:Geneva," which involved him in a somewhat keen controversy in regard to Calvinism and the suppression of theatrical performances within the See also:town. During the time he was engaged on the Encyclopaedia he wrote a number of literary and philosophical See also:works which extended his reputation and also exposed him to See also:criticism and controversy, as in the See also:case of his Melanges de Philosophic, d'Histoire, et de Litteralure. His Essai sur la societe des Bens de lettres avec See also:les grands was a worthy vindication of the See also:independence of literary men, and a thorough exposure of the evils of the See also:system of patronage. He See also:broke new ground and showed great skill as a translator in his Traduction de quelques morceaux choisis de Trcite. One of his most important works was the Elements de Philosophic published in 1759, in which he discussed the principles and methods of the different sciences. He maintained that the See also:laws of motion were necessary, not contingent. A See also:treatise, Sur la destruction des restates (1765), involved him in a fresh controversy, his own See also:share in which was rendered very easy by the violence and extravagance of his adversaries. The See also:list of his more noteworthy literary works is completed by the mention of the Histoire des membees de l'Academie francaise, containing See also:biographical notices of all the members of the Academy who died between 1700 and 1772, the year in which he himself became secretary. Alembert was much interested in See also:music both as a science and as an See also:art, and wrote Elements de musique theorique et pratique (1779), which was based upon the system of J.

P. See also:

Rameau with important modifications and differences. Alembert's fame spread rapidly throughout See also:Europe and procured for him more than one opportunity of quitting the See also:comparative retirement in which he lived in Paris for more lucrative and prominent positions. The offer of Frederick the Great has already been mentioned. In 1762 he was invited by . See also:Catherine of See also:Russia to become See also:tutor to her son at a yearly See also:salary of See also:loo,000 francs. On his refusal the offer was repeated with the additional inducement of See also:accommodation for as many of his See also:friends as he See also:chose to bring with him to the See also:Russian See also:capital. Alembert persisted in his refusal, and the See also:letter of Catherine was ordered to be engrossed in the minutes of the French Academy. In 1755, on the recommendation of See also:Pope See also:Benedict XIV., he was admitted a member of the See also:Institute of See also:Bologna. A See also:legacy of £200 from See also:David See also:Hume showed the esteem in which he was held by that philosopher. Alembert continued to the end to See also:lead the quiet and frugal See also:life dictated by his limited means as well as his See also:simple tastes. His later years were saddened by circumstances connected with a romantic See also:attachment he had formed for Mademoiselle de See also:Lespinasse, whose acquaintance he made at the house of Madame du See also:Deffand, a noted resort of literary men and savants.

She nursed him assiduously during an illness he had in 1765, and from that period till her See also:

death in 1776 they lived in the same house without any See also:scandal. On her See also:part there seems to have been from first to last nothing more than warm friendship, but his feelings towards her were of a stronger See also:kind and her death deeply affected him. He never recovered his See also:elasticity of. See also:Spirits, though he continued to occupy himself with his favourite pursuits, and to frequent the society of his See also:brother philosophers. After the death of See also:Voltaire (1778), whose friend and correspondent he had been for more than thirty years, he was regarded as the 'eader of the philosophical party in the Academy. He died at Paris on the 29th of See also:October 1783. The See also:chief features of Alembert's See also:character were benevolence, simplicity and independence. Though his income was never large, and during the greater part of his life was very meagre, he contrived to find means to support his foster-mother in her old age, to educate the See also:children of his first teacher, and to help various deserving students during their college career. His cheerful conversation, his See also:smart and lively sallies, a singular mixture of malice of speech with goodness of See also:heart, and of delicacy of wit with simplicity of See also:manners, rendered him a pleasing and interesting See also:companion; and if his manner was sometimes See also:plain almost to the extent of rudeness, it probably set all the better an example of a much-needed reform to the class to which he belonged. The controversy as to the nature of his religious opinions, arising as it did chiefly out of his connexion with the Encyclopaedia, has no longer any living See also:interest now that the Encyclopaedists generally have ceased to be regarded with unqualified suspicion by those who See also:count them-selves orthodox. It is to be observed, moreover, that as Alembert confined himself chiefly to mathematical articles, his work laid him less open to charges of See also:heresy and infidelity than that of some of his associates. The fullest See also:revelation of his religious convictions is given in his See also:correspondence with Voltaire, which was published along with that with Frederick the Great in Bossange's edition of his works.

The scientific works of Alembert have never been published in a collected See also:

form. The most important of them have been mentioned above, with the exception of the Opuscules mathematiques (i761-178o), 8 vols. 4to. His literary and philosophical works were collected and edited by Bastien (Paris, 18os, 18 vols. 8vo). A better edition by Bossange was published at Paris in 1821 (5, vols. 8vo). The best See also:account of the life and writings of Alembert is contained in See also:Condorcet's Eloge, presented to the Academy and published in 1784.

End of Article: ALEMBERT, JEAN LE ROND

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