LAPLACE, PIERRE flION, Marquis de e 1749 1s271. The greatest of the French astrono mers. lie was born at Beaumont-en-.Auge (Calvados). His father, a poor farmer. was unable to give him any educational advan tages, but, probably through the generosity of friends, he was able to carry on his studies in the t ollege of Caen and the Shill:try School at Beaumont. Jn the latter institution he was for a short time a teacher of mathematics, but at the age of eighteen he resolved to try his fortune in Paris. 11a ving secured the at Idaho' of ITAletn Imrt (q.v.), then in the height of his power, lie was, on the latter'• recommendation, made professor of mathematics in the Ecole Scarcely twenty year- of age, his remarkable power of mathematical analysis had already be conic Manifest in his /,'«qo rehes .er• it caleul inh'gral (1766-0). These researches were fol lowed by a series of brilliant memoirs on the theory of probability, which immediately at tracted the attention of the scientifie world, and were the object of special commendation by the Academy of Sciences. As a result of their pub lieation, Laplace was in 1773 made an associate and in 1783 a member of this distinguished body. In 1784 he succeeded Bi(zout as examiner in the Royal Artillery Cor(ns. and in 1794 was made professor of analysis at the Ecole Normale. After the organization of the new institute, lie received. through the excellency of his style as shown in his tiystemc du monde, a place among 'the forty' of the Academy in 1816. and in 1817 was made its president. Laplace was not with out political ambition. and did hat hesitate to resort to flattery to secure place. Na 11(110011 made him Minister of the :Inte•ior in 1799, but after six weeks he was compelled to dismiss him with the epigrammatic remark that he carried the spirit of the infinitesimal into his administra tion. lle was recompensed. however. by a seat in the Senate, of which body he later became the vice-president, and chancellor in 1503. In 1:04 the Emperor also created him a count. Ills po litical views conveniently shifting, with the change of power, he received his reward from Louis by being elevated to the peerage with the title of marquis. Ile was a member 11795). and a little later became president. of the Bureau of Longitudes; was president of the commission for reorganizing the Ecole P(dyte•h nique; was a member of the eon mission to estab lish the metric system, a grand officer of the Legion of 'Honor. and a member of most of the prominent learned societies of the world. La place was indefatigable in his scientifie labors and richly deserved the honors which they to hint. Ile has justly been called 'the Newton of France,' the titanic geometer,' and `the greatest mathematieian of his age.' Self sutlieient in the presence of his fellows, lie was humble in his contemplation of the great domain in which he labored. his humility showing itself in the dying words aseribed to him: we know is little. what we do not know is immense." Laplace was celebrated ehielly for his labors in celestial meehanies, especially in relation to the lunar theory. the opposite inequalities of the
motions of Jupiter and Saturn, the question of the tides. and the general problem of the stabil ity of the solar system. The conciliation of the results of observations on the motions of Jupiter and Saturn, to the Newtonian theory, had baffled even Eider and it was the failure of such eminent predecessors that led him as a young man to study the subjeet. The results of his investigations were given when he was only twenty-three years old, in a memoir read before the Academy of Sciences, entitled Sur les solu tions particali(res des I'quat ions di 11YrtnlitlItS it sin' Ins riu'qualit es des This N‘a., by a series I if brilliant dis coveries in the planetary theory. It was in con nection with extended investigation that Laplace discovered in 1786 the del(endenee of the inoon's acceleration upon the secular changes in the eccentricity of the earth's orbit, the key .stone in the theory of the stability of the solar system. Ile also announced the laws of motion if the first three moons of Jupiter, in a form since known as the 'Laws of Laplace': (1) The sum of the mean movement of the first satellite and of twice the third equals three times that of the second: (2) the sum of the mean longitude of the first satellite and of double that of the second diminished by three times that of the third. equals 180°. Laplace's most celebrated treatise is the .111('eanique rag:sir (5 vols., 1799 1S23; trans. by Bowditch. 4 vols., Boston, 1829 39). The aim of this work was to give a (20111 plete solution of the great mechanical problem of the solar system. and to bring the results of ob servation into harmony with the Newtonian hy pothesis. The work will stand as one of the world's greatest contributions to scienee. At the same time it cannot be denied that it has two serious faults. In the first place. Laplace has justly been blamed for not recognizing the un questionable discoveries of his predece,mrs and contemporaries. inferentially appropriating them as his own. The second blemish on the work is the fact that there are many serious omissions in the theory. covered by the frequently recurring expression. 'lit is easy to sec.' These two defects in the work were in part removed by the admir able English translation mentioned above. La place's Expoxition du systolic du monde (1790) was called by Arago the ifecanique celeste, dis robed of its analytic attire. The work is more popular and clear, and is especially valnable for its condensed but masterly ri•suinc of the his tory of astronomy to the close of the eighteenth century. In this work appeared the famous nebular hypothesis (see COSMOGONY), an hy pothesis so foreign to Laplace's habit of mathe matical treatment as to lead him to the apolo geti• statement that it was suggested "with the mistrust whi•ll should inspire everything that is not a result of observation or calculation:" but to it he frequently alludes as highly probable.