Origin of Mountians. 438 
appears to have been a true geanticlinal elevation of the Rocky 
Mountain mass, itself mainly, if not wholly, a combination of 
synelinoria. 
that only feeble flexures of vast span are possible, even if the 
lateral pressure from contraction had not also declined in force. 
4. How was the lateral thrust from the direction of the ocean 
made to differ in its action or results from that from the 
opposite direction ? 
The fact of a difference in the effects of the lateral thrust 
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greatest on the border of the largest oceans. 
But has this greater effectiveness of lateral thrust from the 
direction of the ocean been due to a proportionally greater con- 
traction and subsidence of the oceanic crust than the continental 
—the sinking causing the oceanic arch to pre against the sides 
of the basin. I formerly made this the chief means of moun- 
tain lifting; and now, while not giving it so great prominence, 
