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it could force them momentarily from their positions beneath 
the sea level. But if we suppose a mass of rocks acting 
from beneath by an expansive tendency, there is no difficulty 
in comprehending how a range of mountains might be 
forced upwards, and sustained there. When we consider 
the submergence of the mountains, we have a very difficult 
problem to explain. Mountains could not sink unless they 
had a vacant space into which to sink, and how is this 
vacant space to be obtained? We could only obtain a 
vacant space by assuming the withdrawal of the cause that 
produced the elevation ; by the shrinking up of the rock 
that had expanded, if we grant an expansion, or by the 
perpetual shrinking, if we grant only the sinking probability. 
The sinking theory obliges us to make very many guesses 
and assumptions, and is more intricate than the elevation, 
which requires but one cause to be continued to produce all 
the effects. Assuming for a moment, that as the interior 
of the earth is of a density equal to nearly treble that of 
granite, there is an effort going on to relieve this density, 
then it would follow as a mathematical law, that the exerted 
force would act with the greatest intensity upon that 
portion of the earth's surface which was nearest to the 
centre, and thus, other conditions being the same, that 
portion of the land which was at the time the bed of the 
deepest sea, would be acted upon with greater power than 
the land which was farther removed from the centre, and 
thus by a self-adjusting system the various portions of the 
earth would be raised in turn, and would become mountains, 
plains, valleys, or ocean beds, and thus the transferral of 
the water would be effected. 
Geology, fortunately, is a science which rests upon facts, 
an examination of which will probably render us inde- 
pendent of mere probabilities, and may yield us some sub- 
stantial evidence connected with the subject under discussion. 
