THE EARTH FRAME 
207 
its shape. All worlds are round. Nature is 
intent upon building for eternity, and it chooses 
the strongest building principle of all—the self- 
supporting globe. 
We cannot see upon the globe itself the great, 
sweeping lines that make the earth circle, but, 
as intimated some chapters back, we may gain 
some suggestion of them from certain sky 
curves. The upward and inward arch of the 
blue sky, the visible envelope of the earth, but 
repeats the curve of the earth itself. Nothing 
gives the feeling of the globe’s rotundity so ef- 
fectively as this ; and yet I have been told by 
many observant people that they could not see 
this curve of the heavens, that the blue looked 
to them perfectly flat, and that the monotone 
of the color, the brilliancy of the light, de- 
stroyed all sense of form. Perhaps the curve 
would be apparent to thém if they saw it cast 
upon the sky by the earth’s shadow instead of 
suggested in the illuminated blue. This can 
be seen almost any summer evening, when the 
sky is free of clouds and the sun has just fallen 
below the horizon. Facing to the north and 
looking at the zenith, we are aware of the light 
slowly fading out of the west. Everyone sees 
and knows that fading light, but few of us ever 
Earth lines. 
