266 THE POPULAR SCIENCE MONTHLY. 



he delivered in the Academy on photometry and polarization, and 

 which wore collated by Langier and published with his works. A 

 final experiment, which was made under his direction a short time 

 before his death, was to determine the relative velocity of light 

 through the air and through water. Upon it was thought to hang one 

 of the crucial arguments as between the corpuscular and undulatory 

 theories. The result — determining that light moves more swiftly 

 through the air — was in harmony with the undulatory theory. 



Arago's contributions to scientific literature are to be found scat- 

 tered as special papers recording his experiments, or brief treatises, in 

 the "Memoirs of the Academy of Sciences," the "Menioires de la So- 

 ciete d'Arcueil," the " Annales de Physique et de Chimie," the " An- 

 nuaire du Bureau des Longitudes," where his "Scientific Notices" 

 appeared, and in the reports of his lectures of the observatory, which 

 are embodied in the " Popular Astronomy." They were never arranged 

 by him, but were collected after his death, and published in 1856-'57, 

 in fourteen volumes, of which the " Popular Astronomy " forms the 

 principal part. His chief work in science was in making special inves- 

 tigations, resulting often in brilliant discoveries, which served as the 

 foundation and support of accepted theories. Besides this, he pos- 

 sessed a rare gift, which his friends and biographers claim to be an 

 equal and a specific title of glory, of making scientific truths and con- 

 ceptions comprehensible to the multitude, and this without sacrificing 

 the dignity of science. He was a member of all the learned societies 

 of Europe, and the particular friend of many foreign scientific men. 



The best part of Arago's time was given, according to M. Jamin, 

 to the duties of his professorship in the Polytechnic School. " In this 

 often exacting position, he did not cease to be the object of affection 

 for his good heart, and of admiration for the vigor of his teaching, the 

 ease of his elocution, and the lucidity of his demonstrations. A for- 

 mer pupil himself, he loved his young comrades. It might be affirmed 

 that he was an example to them by his thorough uprightness, judicial- 

 mindedness, disinterestedness, and patriotism, qualities which he com- 

 municated, and which became as it were permanent characteristics of 

 thai admirable school. He defended it on every occasion, extolled it 

 and looked at everything in its light. "Whoever had come out from it 

 was sure of kindness from him. On occasions of difficulty, when a gen- 

 eral excitement threatened the discipline and future of the school, the 

 pupils would go to the observatory for advice and protection, and 

 were sure of getting them. lie excited like admiration and found like 

 esteem at the observatory." His weakness was, that he was subject to 

 transitory fits of passion, which passed away and left no lasting trace. 



