44 
NATURE FOR ITS OWN SAKE 
Shadow 
complica- 
tions. 
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 ght 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 
hnes 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 
isa 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 
