138 



COLOR 



132. Pure, Simple Colors Things as they Seem. To the 



eye white light appears a simple, single color. It reveals its 

 compound nature to us only when passed through a prism, 

 when it shows itself to be compounded of an infinite number 

 of colors which Sir Isaac Newton grouped in seven divisions : 

 violet, indigo, blue, green, yellow, orange, and red. 



We naturally ask ourselves whether these colors which 

 compose white light are themselves in turn compound ? To 

 answer that question, let us very carefully insert a second 

 prism in the path of the rays which issue from the first prism, 

 carefully barring out the remaining six kinds of rays. If the 

 red light is compound, it will be broken up into its constit- 

 uent parts and will form a typical spectrum of its own, just as 

 white light did after its passage through a prism. But the red 

 rays pass through the second prism, are refracted, and bent 

 from this course, and no new colors appear, no new spectrum 

 is formed. Evidently a ray of spectrum red is a simple 



color, not a compound 

 color. 



If a similar experi- 

 ment is made with the 

 remaining spectrum 

 rays, the result is 

 always the same : the 

 individual spectrum 

 colors remain simple, 



Green, blue, pure Colors. T '// e 



individual spectrum 



FlG. 88. Violet and green give blue, 

 and red give white. 



colors are groups of simple, pure colors. 



133. Colors not as they Seem Compound Colors. If one 

 half of a cardboard disk (Fig. 88) is painted green, and the other 

 half violet, and the disk is slipped upon a toy top, and spun rap- 

 idly, the rotating disk will appear blue ; if red and green are 



