44 



NATURE FOR ITS OWN SAKE 



of countenance. A pure color in nature is 

 always more or less bleached, grayed, silvered, 

 or gilded changed at least from its original 

 estate by these conditions. "What might be 

 the green of a maple-tree lighted by sunlight 

 alone is one thing ; what it is lighted by sun- 

 light, sky-light, and reflected light from the 

 earth, not to mention atmospheric influence, 

 is quite another thing. When all the factors are 

 considered, we have anything but a pure green 

 in the tree. It is, doubtless, a mingling of many 

 hues that favors the mauve, the rose, and the 

 lilac shadows. But then, again, they seldom 

 appear unless the day is hot and the air thick, 

 which leads one to think that atmospheric re- 

 flection plays some part in their production. 

 The cause can be conjectured only, but there is 

 no doubt about the effect. The colored shadow 

 is a reality, though its recent discovery finds 

 people still somewhat sceptical about it. 



We have seen that clear light is favorable to 

 the sharp-cut shadow, and that when the light 

 is more widely diffused by atmosphere, or in- 

 creased by reflection, the shadow begins to 

 lighten, to become vague and soft on the edges, 

 and to be enveloped by a penumbra. When the 

 light is still more widely diffused and broken 



