HISTORY OF OPTICS 



CHAPTER XL 



EPOCH OF YOL'XG AND FRESXEL. 



Sect. i. Introduction. 



nillE man whose name must occupy the most distinguished place ir. 



the history of Physical Optics, in consequence of what he did in 



reviving and establishing the uudulatory theory of light, is Dr. Thomas 



Young. He was Lorn in 1773. at Milverton in Somersetshire, of 



O ' 7 



Quaker parents ; and after distinguishing himself during youth by the 

 variety and accuracy of his attainments, he settled in London as a phy- 

 sician in 1801 ; but continued to give much of his attention to general 

 science. His optical theory, for a long time, made few proselytes ; 

 and several years afterwards, Auguste Fresnel, an eminent French 

 mathematician, an engineer officer, took up similar views, proved their 

 truth, and traced their consequences, by a series of labors almost inde- 

 pendent of those of Dr. Young. It was not till the theory was thus 

 re-echoed from another land, that it was able to take any strong hold 

 on the attention of the countrymen of its earlier promulgator. 



The theory of undulations, like that of universal gravitation, may 

 be divided into several successive steps of generalization. In both 

 cases, all these steps were made by the same persons ; but there is this 

 difference ; all the parts of the law of universal gravitation were 

 worked out in one burst of inspiration by its author, and published at 

 one time ; in the doctrine of light, on the other hand, the different 

 steps of the advance were made and published at separate times, with 

 intervals between. We see the theory in a narrower form, and in 

 detached portions, before the widest generalizations and principles of 

 unity are reached ; we see the authors struggling with the difficulties 

 before we see them successful. They appear to us as men like our- 

 selves, liable to perplexity and failure, instead of coming before us, as 

 Xewton does in the history of Physical Astronomy, as the irresistible 

 and almost supernatural hero of a philosophical romance. 



