VIII 
PRIMAL ENERGIES 
OW puny and meagre is the utmost power man 
can put forth, even by the aid of all his 
mechanical appliances, when compared with the 
primal earth forces! Think, or try to think, of the 
force of pressure that causes the rock-strata to 
buckle or crumple or bend — layers of rock, thou- 
sands of feet thick, made to fold and bend like the 
leaves of a book —vast mountain-chains flexed and 
foreshortened, or ruptured and faulted as the bend- 
ing of one’s body wrinkles or rips one’s clothes. 
Think of the over-thrusts and the folding and shear- 
ing of the earth’s crust. The shrinking of the earth 
squeezes the rocks to an extent quite beyond our 
power of conception. “So overpowering has been 
the horizontal movement in some cases,” says 
Dana, “that masses of rock thousands of feet in 
thickness have been buckled up and sheared, or, 
simply yielding to pressure, have sheared without 
folding, and been thrust forward for miles along a 
gently inclined plane. These great reversed faults 
are termed over-thrusts or thrust-planes. Some- 
times such thrust-planes occur singly, at other times 
the rocks have yielded again and again, great sheets 
having been sliced off successively, and driven for- 
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