20 PROCEEDINGS OP THE AMERICAN ACADEMY 



Faraday of the rotatory influence imparted to glass when exposed to 

 the constraint of electro-magnetic induction. 



Biot was the ablest champion of the corpuscular theory of light. 

 By his celebrated hypothesis of movable polarization, which fills the 

 entire volume of the Academy of Science for 1812, he succeeded in 

 giving a formal explanation to the phenomena of depolarization, and of 

 delaying for a time the triumph of the theory of undulations. In this 

 attempt he had the sympathy of Laplace and other prominent mathe- 

 maticians, who found the speculations of Biot more congenial to their 

 habits of thought than the theory of Fresnel. Arago, however, soon 

 entered the lists against Biot, and the discussion was carried on with 

 such bitterness that these distinguished physicists, once intimately asso- 

 ciated, were wholly estranged from each other. It may be inferred, 

 however, from the reflections of Biot in his Melanges Scientijiques et 

 Litteraires, that, if he were not altogether converted to the undulatory 

 theory of light, he could not but acknowledge the wonderful felicity 

 with which Fresnel had adapted it to the various classes of phenomena 

 with which experimental research had enriched the domains of optics 

 within the present century. 



Few salient points present themselves in the even tenor of a life 

 dedicated to the unostentatious pursuit of science, as that of Biot was 

 par excellence. In 1804, Biot and Gay-Lussac proposed to ascend in 

 a balloon to the higher region of the air, to measure the force of 

 terrestrial magnetism at gi'eat elevations, and to experiment upon 

 the chemical and electrical properties of the atmosphere at different 

 heights. By the instigation of Berthollet and Laplace, aided by the 

 influence of the great chemist Chaptal, who was then Minister of the 

 Interior, the government gave its support to the projected enterprise ; 

 and one of the celebrated balloons of Conte, which had survived Na- 

 poleon's campaign in Egypt, was intrusted to the scientific explorers, 

 and the artist who constructed it was placed at their disposal to pre- 

 pare it for its peaceful ascent. Supplied with a full complement of 

 barometers, thermometers, hygrometers, electrometer, and instruments 

 for measuring the magnetic force and dip, as well as frogs, insects, and 

 birds for galvanic experiments, the scientific voyagers embarked in 

 their aerial car on the 23d of August, 1804. They began their experi- 

 ments at the altitude of 6,500 feet, and continued them up to the alti- 

 tude of 13,000 feet, and with a success commensurate with their wishes. 

 The last part of the excursion, and especially the landing which they 



