A HISTORY OF SCIENCE 



To Hooke's contemporary, Huygens, who was the 

 originator of the general doctrine of undulation as the 

 explanation of light, Young renders full justice also. 

 For himself he claims only the merit of having demon- 

 strated the theory which these and a few others of his 

 predecessors had advocated without full proof. 



The following year Dr. Young detailed before the 

 Royal Society other experiments, which threw addi- 

 tional light on the doctrine of interference; and in 1803 

 he cited still others, which, he affirmed, brought the 

 doctrine to complete demonstration. In applying this 

 demonstration to the general theory of light, he made 

 the striking suggestion that "the luminiferous ether 

 pervades the substance of all material bodies with little 

 or no resistance, as freely, perhaps, as the wind passes 

 through a grove of trees." He asserted his belief also 

 that the chemical rays which Ritter had discovered 

 beyond the violet end of the visible spectrum are but 

 still more rapid undulations of the same character as 

 those which produce light. In his earlier lecture he 

 had affirmed a like affinity between the light rays and 

 the rays of radiant heat which Herschel detected below 

 the red end of the spectrum, suggesting that "light 

 differs from heat only in the frequency of its undu- 

 lations or vibrations those undulations which are 

 within certain limits with respect to frequency affect- 

 ing the optic nerve and constituting light, and those 

 which are slower and probably stronger constituting 

 heat only." From the very outset he had recognized 

 the affinity between sound and light; indeed, it had 

 been this affinity that led him on to an appreciation 

 of the undulatory theory of light. 



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