444 HISTORY OF OPTICS. 



The mathematical treatment of the question on the 

 latter hypothesis was by no means easy. Young 

 was a mathematician of considerable power in the 

 solution of the problems which came before him : 

 though his methods possessed none of the analytical 

 elegance which, in his time, had become general in 

 France. But it does not appear that he ever solved 

 the problem of undulations as applied to fringes, 

 with its true conditions. He did, however, rectify 

 his conceptions of the nature of the interference ; 

 and we may add, that the numerical errour of the 

 consequences of the defective hypothesis is not 

 such as to prevent their confirming the undulatory 

 theory (KA). 



But though this theory was thus so powerfully 

 recommended by experiment and calculation, it met 

 with little favour in the scientific world. Perhaps 

 this will be in some measure accounted for, when 

 we come, in the next chapter, to speak of the mode 

 of its reception by the supposed judges of science 

 and letters. Its author went on labouring at the 

 completion and application of the theory in other 

 parts of the subject ; but his extraordinary success 

 in unravelling the complex phenomena of which we 

 have been speaking, appears to have excited none of 

 the notice and admiration which properly belonged 

 to it, till Fresnel's Memoir On Diffraction was deli- 

 vered to the Institute, in October, 1815. 



MM. Arago and Poinsot were commissioned to 

 make a report upon this Memoir ; and the former 



