XV 

 GREAT QUESTIONS IN LITTLE 



I. THE ETHER 



TO speak of invisible rays of light seems a con- 

 tradiction of terms, and so it would be were 

 light rays an objective reality instead of an experi- 

 ence of our consciousness. The dark, or heat, rays 

 of the spectrum are as real as the light rays, but we 

 see them not because our eye is not attuned to 

 them, or in their key. It is said that the Leyden 

 jar emits rays that obey all the laws of optics, but 

 the eye is no wiser for it. Light is created in the 

 eye, as sound is born in the ear. Certain vibrations 

 in the ether give us a sensation that we name 

 "light"; certain vibrations in the air give us sensa- 

 tions that we call "sound." All the color in nature 

 is the result of what the vibrations reflected from 

 objects do to the eye, just as all we call sound is the 

 result of what certain mechanical disturbances in 

 the air do to the ear. There is no color in the dark 

 and there is no sound in a vacuum. We can set up 

 a mechanical disturbance in the air, but we cannot 

 set up a mechanical disturbance in the ether, be- 

 cause the ether is not a tangible body. It defies 

 all our definitions of tangible bodies. No device or 

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