THE EARTIT FRAME 
199 
earth. If it were not for them there would be 
more Saharas of desolation, and the green of 
the earth in many a tract now lovely in light 
and color, would take wings and vanish into 
space. It is color that gives the glow of life to 
the earth, and yet this great beauty might dis- 
appear without weakening in any way the frame 
or form of the globe. The earth could and 
would exist, and swing on in its orbit, were 
there no life, no light, no color upon it. The 
modelling of the mountains, the deep-incised 
river valleys, the flat spaces of the plains, the 
hollow depths of the ocean-beds, would remain 
substantially as to-day. For the material of 
which the earth is formed is so cohesive that 
its shape would probably hold for centuries 
after its seas had evaporated and its atmos- 
phere had passed away. The interior of the 
globe may be fire or rolling vapors, or simply 
solid matter; man speculates about it without 
absolute knowledge. But about the crust he is 
quite certain that it is rock formation, made 
in different ways and at different geological 
periods of the earth’s history. 
Doubtless, the whole globe was at one time 
covered with sea, and when the waters receded 
from the table-lands there was a hardening of 
The earth's 
skeleton. 
Its strength. 
