The Evolution of Optics. 265 



of light, and in his hands the wave-theory fell but little 

 short of that positive demonstration which it was destined 

 to receive years after from Young and Fresnel. 



Newton urged against the wave-theory that, were it true, 

 light should bend round opposing obstacles, as do the waves 

 of sound, and this objection Young for the first time satis- 

 factorily answered. 



From a- careful study of the phenomena of sound, he was 

 led to a comprehension of the phenomenon of the interfer- 

 ence of light- waves. He showed that such a bending of the 

 waves as Newton had suggested did take place, but that 

 the light was destroyed by the mutual interference of the 

 waves. He showed that light added to light under certain 

 circumstances could produce darkness, just as sound added 

 to sound may produce silence. 



There is, perhaps, no man of equal merit so little known 

 and appreciated as Dr. Thomas Young, whose name is so 

 intimately associated with the development of the undula- 

 tory theory of light. In Music, Art, Literature, and Sci- 

 ence he was illustrious. The unraveling of the puzzle of 

 the Egyptian hieroglyphics was an achievement upon which 

 any man might have rested his claim to distinction, yet this 

 was but one of Young's interests. 



The wave-theory of light has proved a key for the un- 

 locking of Nature s language. It has done for the science 

 of optics what Young's reading of the Rosetti stone did for 

 the meaningless hieroglyphics; it has made all the phe- 

 nomena of light intelligible ; it has reduced a jumble of 

 curious facts to an eloquent demonstration of scientific 

 truth. Yet Young was scarcely known to his contempo- 

 raries. It was sufficient to say, " "Who is this man that pre- 

 tends to be greater than Newton ? " and the upstart and his 

 work became objects of popular contempt. But the theory 

 could not be thus snuffed out, although Young might be 

 temporarily deprived of his due share of credit. 



About this time Fresnel, a young French engineer, was 

 pursuing investigations which led to similar results. He 

 likewise demonstrated the truth of the wave-theory, and to 

 him is usually assigned the honor of its discovery, but, be it 

 said to his credit, he fully acknowledged Young's claim to 

 priority. 



The labors of Young and of Fresnel served to establish the 

 wave-theory of light, than which few more important hy- 

 potheses have ever been enunciated. It embraces at once 

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