36 ORGANIC EVOLUTION CONSIDERED 



consisting of all the colors of the rainbow, and invis- 

 ible rays beyond the violet, all arranged in definite 

 order according to their rates of vibration. 



As in music the different notes depend on different 

 rates of vibration of air, so the different colors are 

 due to the different rates of the vibrations of ether. 



We know from experience that many notes may be 

 sounded at once and all be audible to the ear. The 

 air as a medium responds readily at the same time 

 to many different rates of vibration, so that the ear 

 can distinguish them as separate notes. 



So ether responds to the many rates of vibration 

 which are necessary to produce the heat and light and 

 actinic rays that reach us from the sun. We some- 

 times speak of the seven colors of the rainbow, but 

 this is simply a convenience, for the number is indef- 

 initely great. They shade so gradually one into 

 another in the rainbow that it is impossible for the 

 eye to draw definite lines between them. This vast 

 number of colors, together with the multitude of 

 rates of vibrations that represent the different de- 

 grees of heat and of actinic rays, show that the 

 motions of the ether, as represented in the rays of the 

 sun, are inconceivably complex. 



And when in addition to this we remember the fact 

 that hundreds of thousands of stars have been seen, 

 and that in order to see them the ether must respond 

 at one and the same time to separate vibrations from 

 all of these bodies scattered through infinite space, 

 the methods of vibration become infinitely complex. 



Instead of waves like those of sound, varying from 

 half an inch to 70 feet in length, we find from forty 

 thousand to sixty thousand waves in the length of one 

 inch. How infinitely delicate must be the organ of 

 sight that it may appreciate such extremely small 

 disturbances of a medium so subtle and attenuated 



