MOUNTAINS 325 
one of the theories does this, that there are so many 
explanations before us. In a book of this scope it 
will be impossible to do justice to the various theories 
of mountain development, and so we must be con- 
tented with the mere statement of the most prominent 
theory, and the reasons why to a very large number 
of geologists it seems the best hypothesis yet offered. 
It must be understood that there are arguments against 
it, that many do not accept it, and that it is merely 
a theory, or perhaps not more than a hypothesis. 
Fie. 194. 
Imitation mountain folds produced artificially by subjecting layers of wax 
to a pressure from one side. 
As originally stated, this contractional hypothesis 
was, that as the molten interior of the earth slowly 
cooled, it contracted, and the solid outer crust wrinkled 
in its constant attempt to surround the molten inner 
sphere, which was ever becoming smaller. With the 
general abandonment of the theory that the interior of 
the earth is molten, this hypothesis needed modification ; 
but it is still essentially the same, if we merely substi- 
tute for the globe of molten rock, a highly heated, 
but solid interior. About this, the solid crust, which 
