306 A Short History of Astronomy [CH. xi. 



to a large number of papers on astronomy and mathematics, 

 three important books on pure mathematics,* and at the 

 time of his death had not quite finished a second edition 

 of the Mecanique Analytique, the second volume appearing 

 posthumously. 



238. Pierre Simon Laplace, the son of a small farmer, 

 was born at Beaumont in Normandy in 1749, being thus 

 13 years younger than his great rival Lagrange. Thanks 

 to the help of well-to-do neighbours, he was first a pupil 

 and afterwards a teacher at the Military School of his 

 native town. When he was 18 he went to Paris with a 

 letter of introduction to D'Alembert, and, when no notice 

 was taken of it, wrote him a letter on the principles of 

 mechanics which impressed D'Alembert so much that he 

 at once took interest in the young mathematician and 

 procured him an appointment at the Military School at 

 Paris. From this time onwards Laplace lived continuously 

 at Paris, holding various official positions. His first paper 

 (on pure mathematics) was published in the Transactions 

 of the Turin Academy for the years 1766-69, and from this 

 time to the end of his life he produced an uninterrupted 

 series of papers and books on astronomy and allied de- 

 partments of mathematics. 



Laplace's work on astronomy was to a great extent 

 incorporated in his Mecanique Celeste, the five volumes 

 of which appeared at intervals between 1799 and 1825. 

 In this great treatise he aimed at summing up all that had 

 been done in developing gravitational astronomy since the 

 time of Newton. The only other astronomical book which 

 he published was the Exposition du Systeme du Monde 

 (1796), one of the most perfect and charmingly written 

 popular treatises on astronomy ever published, in which 

 the great mathematician never uses either an algebraical 

 formula or a geometrical diagram. He published also in 

 1812 an elaborate treatise on the theory of probability or 

 chance,t on which nearly all later developments of the 

 subject have been based, and in 1819 a more popular 

 Essai Philosophique on the same subject. 



r * Theorie dcs Fonctions Analytiqucs (1797); Resolution dcs 

 Equations Numeriques ( \ 798) ; Lemons sur le Calcul dcs Fonctions 

 (1805). f Theorie Analytique des Probabi life's. 



