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 LAPLACE heat, his discovery of the cause of the discre- pancy between the theoretical and observed velocity of sound, his rules for barometrical measurement, and his theories regarding capil- lary attraction, tides, and atmospheric refrac- tion, show that in some of the most impor- tant branches of general physics his mind was not less actively and profitably employed than in mathematical analysis. The crowning glo- ry of his scientific career was his Mecanique celeste, a book which has been truly said to have had no predecessor, and which must wait for a second Laplace to arise ere it finds a rival. In it he sought to digest on a uniform scientific basis the abundant materials relating to the application of analysis to physical astronomy, which had been accumulating during nearly a century, and which, written in various lan- guages, with differing notations and in vari- ous stages of scientific progress, presented a mass of matter not only difficult of access, but almost incomprehensible to any but the most recondite student. The result of his labors appeared in 16 books, published in 5 vols. 4to, with four supplements, between 1799 and 1825, and arranged as follows : vol. i. : book i., " On the General Laws of the Equilibrium of Motion ;" book ii., " On the Law of Uni- versal Gravitation and the Motion of the Cen- tres of Gravity of the Heavenly Bodies ;" vol. ii. : book iii., " On the Figure of the Heavenly Bodies ;" book iv., " On the Oscillations of the Sea and the Atmosphere ;" book v., " On the Motions of the Heavenly Bodies around their Proper Centres of Gravity " (Paris, 1799 ; re- published in 1829-'30) ; vol. iii.: book vi., " On the Theory of the Planetary Motions ;" book vii., " On the Theory of the Moon," and supplement i., " On the two great Inequalities of Jupiter and Saturn " (Paris, 1804) ; vol. iv. : book viii., " On the Theory of the Satellites of Jupiter, Saturn, and Uranus;" book ix., "On the Theory of Comets ;" book x., " On differ- ent Points relative to the System of the World," and supplements ii. and iii., comprising the "Theory of Capillary Action " (Paris, 1805); vol. v. : book xi., " On the Figure and Ro- tation of the Earth ;" book xii., " On the At- traction and Repulsion of Spheres, and the Laws of the Equilibrium and Motion of Elas- tic Fluids ;" book xiii., " On the Oscillation of the Fluids which cover the Planets;" book xiv., " On the Motions of the Heavenly Bodies around their Centres of Gravity ;" book xv., " On the Motions of the Planets and Comets ;" book xvi., " On the Motions of the Satellites," and supplement iv., " On the Development in Series of the Radical which expresses the Mu- tual Distance' of two Planets " (Paris, 1823-'5). " Within this immense programme," says Pro- fessor Nicol, "placed as if parenthetically, one finds the most striking notices on almost every important problem of mechanical physics, any one of which would have made the fortune of an ordinary mathematician." In consequence, however, of his almost total neglect to refer to the labors of his predecessors or contempora- ries in this, and indeed in all his works, it is difficult for the student to know how much of it belongs to Laplace and how much to oth- ers ; and he has therefore, not without appar- ent reason, been sometimes considered more of a compiler than a discoverer. The name of Lagrange, his great contemporary and friend, is rarely mentioned, and one of the latter's finest analytic discoveries is on one occasion cursorily referred to as " the formula No. 21 of the second book of the Mecanique celeste.' 1 ' 1 In like manner the claims of Taylor and Mac- laurin to the theorems passing under their names are ignored, while his references to him- self are innumerable. With all needful resto- rations and acknowledgments, however, almost any one of the original researches of Laplace contained in the Mecanique celeste is sufficient to stamp him as one of the greatest of mathe- maticians. The only translation of this work is that by Dr. Bowditch of Salem, Mass., with full commentaries, published at Boston. (See BOWDITCH, NATHANIEL.) Mrs. Somerville's " Mechanism of the Heavens " is a summary of a portion of the work. Laplace's remaining works consist of his Theorie analytique des prolabilites, the most mathematically profound treatise on the subject which has yet appeared, and containing his celebrated method for the approximation to the values of definite in- tegrals (Paris, 1812; 3d ed ;, 1820, with four supplements); his Exposition du systeme du monde (2 vols. 8vo, 1796 ; 6th ed., containing a eulogium on the author by Baron Fourier, 4to, 1835), "a resume of all modern astronomy, un- surpassed for perspicuity and elegance in any scientific literature," translated by Prof. Pond; and over 40 important memoirs, principally on astronomical subjects, published between 1772 and 1823. Of the three works above named, an edition in 7 vols. 4to (Paris, 1843-'7) was published under government auspices. He died after a short illness. It is commonly related that his last words were : " What we know is of small amount; what we do not know is enormous." But De Morgan states, apparently with authority, that the last words of the great astronomer were different. During his illness, says De Morgan, " he thought much on the great problems of existence, and often muttered to himself, Qu'est ce que c'est que tout cela ! Af- ter many alternations, he appeared at last so permanently prostrated that his family applied to his favorite pupil, Poisson, to try to get a word from him. Poisson paid a visit, and after a few words of salutation said : * I have good news for you. A letter has been received at the bureau of longitudes from Germany, an- nouncing that M. Bessel has verified by obser- vation your theoretical discoveries upon the satellites of Jupiter.' Laplace opened his eyes and answered with deep gravity : * Man pursues nothing but chimeras.' He never spoke again." He has been accused of holding materialistic views ; but his writings give no evidence of a