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THE POPULAR SCIENCE MONTHLY. 



things, and construct a symbolic idea which represents our planet, but 

 we never grasp the reality in the immensity of its proportions. 



Light is a force, and science holds that it is made up of impulses. 

 Nature has been shown to conform all kinds of dynamical effects to 

 rhythmical pulsing, or wave-like action and the impulses of light are 

 held to be of the same kind. There are, at any rate, measurable 

 effects which are unequal in the different colored lights, and the scale 

 has been determined. In an inch of violet light it is shown that there 

 are no less than 57,000 waves, a statement in which there is nothing 

 extraordinary or impossible, as Nobert, the German optician, is in the 

 habit of ruling his microscopical test-glasses at rates all the way from 

 100,000 to 200,000 per inch. But, when we are told that the ray 

 enters the eye at the rate of 185,000 miles per second, and — as each 

 inch contains 57,000 waves — that when we are looking at a violet ob- 

 ject there are 699,000,000,000,000 beats upon the retina each second, 

 the statement baffles all imagination : we may accept, but cannot under- 

 stand it. In the attempt to penetrate the nature of light we are lost 

 in the mysteries of the infinite. Yet the modes of its action have been 

 determined, and they furnish the most splendid example we know of 

 the inflexibleness and exactitude of what are called the laws of Na- 

 ture. 



Fig. 2. 



Image fobmed by a Hole in a Cabd. 



Man is placed in the midst of the universe, and is designed to have 

 knowledge of it. He is impressible to outward agencies, and possesses 

 a grand cerebral treasury -house for storing up these external impres- 



