TIIE BLUE SKY 
49 
into black space, but the color gradations are so 
subtle that we donot perceive the changes from 
one to another. Clouds help us somewhat in 
increasing the feeling of depth, for they are 
perspective points five or six miles on the way 
at least. Sometimes a pillar of cumulus will 
rise in the air thirty thousand feet from base to 
top, and tracing this upward the eye may see 
far above it the drift clouds of the stratus, and 
still higher, like specks upon the blue, the fine- 
spun fibres of the cirrus. This will give some 
idea of distance, though it is not entirely satis- 
factory. The view from Alpine peaks, where 
we are already twelve thousand feet up, and see 
still far above us against a violet sky the white 
spirals of the ice clouds, is not more satisfactory, 
save that in the thinner and clearer air the feel- 
ing of space is greater, and the sky becomes 
more of a blue wilderness than a domed roof. 
We comprehend the breadth and reach of the 
sky perhaps as little as its depth. Our horizon 
is an apparent circle as our zenith is an imagin- 
ary point. The circle is twenty, fifty, or from 
high ground perhaps seventy miles in diameter, 
but we always see its outside limit—the com- 
plete circle—no matter how vast the view. No- 
where is the eye so hemmed in, nowhere does 
Through 
the clouds. 
Sky reach, 
