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CHAPTER XXII 



NOTHIXG can be in appearance more simple and uncom- 

 pounded, or, as it is scientifically expressed, more appar- 

 ently homogeneous, than pure white light. It was the 

 celebrated Sir Isaac Newton who first called the attention 

 of mankind strongly to the fact that a beam of such light 

 can be separated into many component parts, strikingly 

 different from each other in their powers and properties in 

 relation to human vision. It has since been discovered 

 that the radiation from the sun, which was formerly 

 thought to consist of simple beams of light and heat, is 

 infinitely more complicated than even Newton imagined, 

 who only separated the beam of light into the seven prin- 

 cipal colors. 



The discovery of Newton was this: "When light passes 

 out of a rare medium like air into a dense one like glass, 

 or water, or ice or reversely, from any such substance 

 into air, if it enters or emerges obliquely, the ray is bent 

 a little out of the direct line, as you see very clearly when 

 you hold a pole or stick in an oblique position, with the 

 lower end of it in the water. The stick, seen from above, 

 appears bent at the place where it enters the water, on ac- 

 count of the rays which come from that part of it which 

 lies under the water being turned somewhat downward as 

 they emerge, and thus are made to enter the eye as if they 

 came from higher points within the water than they actu- 

 ally do come from. 



For, as has already been explained, things always appear 



