190 PROCEEDINGS OF THE AMERICAN ACADEMY 



wrote from Milan : " The Mecanique Celeste seems to me called to 

 give a new splendor to the age in which we live." On August 12, 

 1812, he wrote from Witepsk: "There was a time when I should 

 have read with interest your Traite da Calcul des Probabilites. To- 

 day, I must limit myself to testifying to you the satisfaction I experi- 

 ence every time I see you communicate new works which perfect and 

 extend the first of the sciences and contribute to the glory of the 

 nation. The advancement and perfectionatiou of mathematics are 

 bound to the prosperity of the state." 



Arago did not imitate the political subserviency of Laplace, much as 

 he admired his genius. In early life he went to Spain with Biot, to 

 complete a geodesic operation. This expedition, though full of adven- 

 ture and danger, had a successful issue, by giving a more precise value 

 to the magnitude of the earth. On his return he was made a member 

 of the Paris Academy when scarcely twenty-three years old. His sci- 

 entific career was brilliant, and in 1830 he replaced Fourier as Perpet- 

 ual Secretary. In 1 848 he espoused the cause of the second republic, 

 with Louis Bonaparte as President. After the second coup d'etat, he 

 refused to take the oath of allegiance to the new government, required 

 of all officials. Nevertheless, he was allowed to retain the post of as- 

 tronomer in the Bureau de Longitude, the new Emperor " making an 

 exception in favor of a savant whose works had thrown lustre on 

 France, and whose life his government would regret to embitter." As 

 Minister of the Marine, Arago had originated and carried an act for 

 abolishing slavery in the French colonies. Being urged to delay the 

 change and make it gradually, he declared, " I will not postpone till 

 to-morrow an act which sets free the oppressed." 



Poisson was of humble origin, but rose to be Peer of France. He 

 befriended Arago, who was five years younger, and who describes him 

 in his youth as of delicate complexion, slight figure, and childish man- 

 ner. At the age of eighteen, he submitted to his teacher, Lagrauge, 

 some amelioration in the method of demonstrating the binomial the- 

 orem, which his teacher read publicly in his lectures, and said he 

 should adopt. Laplace wished to know a geometer who had made 

 such a beginning. Poisson was one of the earliest and the most 

 powerful in applying Fourier's definite integrals and periodic series 

 to physical problems. He extended the conclusions of Lagrange and 

 Laplace on the stability of the solar system, adding millions of years 

 to its probable duration. As there was no vacancy in the French 

 Academy in his proper section, he was placed in that of Physics. 

 Afterwards much of his work was upon physical problems, such as 



