Februaby S, 1895.] 



SCIENCE. 



151 



and closing his remarkable career at the 

 ripe age of seventy-seven. 



Little seems to he known of the ancestry 

 and early life of Laplace. It appears, how- 

 ever, that he was the son of a farmer and 

 that he had achieved some local distinction 

 as a teacher of mathematics at the age of 

 eighteen, when he went np to Paris with 

 such letters of recommendation as he conld 

 get, and applied for a position in the go\ern- 

 nient schools. He appealed to d'Alembert, 

 who was then the leading mathematician at 

 the French capital, but d'Alembert, it is 

 siiid, gave no heed to either the application 

 or the recommendations of the aspirant for 

 office. Thereupon the unknown Laplace 

 wrote the gi-eat geometer a letter on the 

 principles of mechanics which brought an 

 immediate reply. ''You needed no intro- 

 duction or recommendation," said d'Alem- 

 bert, '■ A'ou have recommended j'ourself ; 

 my support is your due." Through the in- 

 fluence of d'Alembert, Laplace was soon 

 given a professor.«hip of mathematics in the 

 militarj' school of Paris, and his scientific 

 career was thus begun. He was not yet 

 twenty-five years of age when lie made one 

 of the most important advances in the his- 

 tory of dynamical astronomy toward the 

 solution of the gi-and problem of the stability 

 of the solar system. By this step be became 

 at once the peer of his older and eminent 

 contemporaries. Euler, d'Alemljert, and La- 

 grange. From this time on until his death 

 in 1827, his indefatigable labors and pene- 

 trating insight brought to light a continuous 

 series of brilliant discoveries. The history 

 of dynamical astronomj-, indeed, for the lialf 

 century ending witli 182.5, is essential!}' the 

 history of the work of Laplace as recorded in 

 his Mi'canlrjur Giede. A pei-sistent and lofty 

 enthusiasm for the system of the world is dis- 

 played in all his works; his latest writings 

 even being no less inspii-ing than his earli- 

 est. His zeal recognized no bounds. " He 

 would have completed the science of the 



skies," says Fourier, '• had that science been 

 capable of completion." He died at the age 

 of seventy-eight, and his last words were 

 worthy of the philosopher he was. " What 

 we know is very little; what we are ignor- 

 ant of is immense." 



Poisson.the youngest of this famous trio, 

 was forty-five years younger than Lagrange 

 and thirty-two j'eai-s younger than La- 

 place. He was born of humlile parent- 

 age at Pitbiviers, in 1781, his father at 

 that time being a petty government ofiicial. 

 While yet an infant, Poisson was con- 

 fided to the care of a neighboring peasant- 

 woman, at whose hands he received rather 

 startling treatment for one who was des- 

 tined to become famous in the annals of 

 science. Poisson relates that his father 

 came one day to see how his son was 

 getting on, and was horrified to find that the 

 peasant-nurse had gone to the fields, leaving 

 the child suspended from the ceiling by a 

 small cord at a height just sufficient to se- 

 cure immunity from the teeth of the swine 

 which, it seems, had ft'ce access to the 

 house. In relating this novel incident in 

 his early life, Poisson used to say that " a 

 gymnastic effort carried me incessantly 

 from one side of the vertical to the other; 

 and it was thus, in my tenderest infancy, 

 that I made my prelude to those studies of 

 the pendulum that were to occupj' me so 

 much in my mature age," 



As the youth gi-cw up, receiving the bare 

 elements of education from his father, the 

 qui'stion was raised in his family as to what 

 calling he should follow. It was suggested 

 that he should become a notary, but the 

 better judgment of the family councils de- 

 cided that the l)usiness of a notary required 

 too much intellectual capacity for the young 

 man, and it was therefore determined to 

 make a surgeon of him. He was appren- 

 ticed to an uncle who practiced the art of 

 blood-letting and l)listering of tliat day, 

 and who set the beginner at work pricking 



