204 COLOR. 



are capable respectively of exciting the green or the blue 

 sensation in our minds when they actually enter our eyes. 

 That they are not green or blue themselves, but only have 

 the power of exciting these sensations in us, is evident from 

 the fact that, when we look out at a window through the 

 air, although the blue rays, as we call them, are coming 

 down through it all the time from the sky above, and the 

 green ones coming up through it from the grass below, we 

 see no blue or green unless we turn our eyes toward the sky 

 or the ground. In other words, the r&ys have no blueness 

 or greenness in themselves, but only have the power of 

 producing the peculiar sensations to which we give those 

 names when they enter our eyes and take effect upon the 

 sensitive organization of the retina. 



It is substantially the same with transparent substances 

 of different colors. Green glnss, for example, absorbs all 

 those portions of the solar ray which have not the power 

 of producing in us the sensation of green, while they allow 

 those that have this power to pass. Accordingly, any 

 thing that we see through such glass appears tinged with 

 green. 



Thus the color of any substance, transparent or opaque, 

 depends upon the part of the solar ray which it reflects or 

 transmits. And this is the philosophy of color, as at pres- 

 ent understood. 



