476 HISTORY OF OPTICS. 



speculations fell in better with the views of the 

 leading mathematicians of Paris. We may con- 

 sider as evidence of the favour with which they 

 were looked upon, the large space they occupy in 

 the volumes of the Academy for 1811, 1812, 1817, 

 and 1818. In 1812, the entire volume is filled 

 with a memoir of Biot's on the subject of moveable 

 polarization. This doctrine also had some advan- 

 tage in coming early before the world in a didactic 

 form, in his Traite de Physique, which was pub- 

 lished in 1816, and was the most complete treatise 

 on general physics which had appeared up to that 

 time. In this and others of this author's writings, 

 he expresses facts so entirely in the terms of his 

 own hypothesis, that it is difficult to separate the 

 two. In the sequel M. Arago was the most pro- 

 minent of M. Biot's opponents; and in his report 

 upon Fresnel's memoir on the colours of crystalline 

 plates, he exposed the weaknesses of the theory of 

 moveable polarization with some severity. The 

 details of this controversy need not occupy us ; but 

 we may observe that this may be considered as the 

 last struggle in favour of the theory of emission 

 among mathematicians of eminence. After this 

 crisis of the war, the theory of moveable polariza- 

 tion lost its ground ; and the explanations of the 

 undulatory theory, and the calculations belonging 

 to it, being published in the Annales de Chimie et 

 de Physique, of which M. Arago was one of the 

 conductors, soon diffused it over Europe. 





