4 



THE NEW KNOWLEDGE. 





ether by a decided negation of belief in its existence. But 

 the fact of the matter is that if this thing " ether " is not 

 visible to the eye of sense it is visible to the eye of the mind, 

 which is much less liable to err. To demonstrate this, 

 place a little instrument known as the radiometer up in the 

 sunlight. This instrument consists of a 

 glass bulb containing a partial vacuum in 

 which hangs poised a tiny mill wheel of 

 aluminum. On the impact of the sunlight 

 the wheel at once begins to revolve, and 

 soon attains a velocity so great that the 

 eye is unable to distinguish the separate 

 vanes. Now the eye of the mind is applied : 

 Something, therefore, flies 93,000,000 of 

 miles from the sun and causes that wheel 

 to revolve, and that something must be 

 the radiations of light and heat. With re- 

 gard to the nature of these radiations we 

 are positively shut up to one of two ex- 

 planations. 



The light and heat proceeding from the sun consist 

 either of particles or of waves. There is no other explana- 

 tion conceivable. 



The first assumption, that they consist of particles, is 

 known as the " corpuscular theory," and was killed out- 

 right and buried years ago after a battle royal. The second 

 assumption, that of waves, known as the undulatory theory, 

 meets with universal acceptance. It is the only complete 

 explanation of all the known facts. The radiations from 

 the sun, therefore, that moved our mill wheel consist of 

 waves; and now comes the inevitable back- thrust of the 

 mind, waves of what? 

 Once convinced that light consists of waves, the mind 



Fig. 1. 



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