They
would rise; and as they rose leave open space between them. Now if
you could contrive to squeeze into them from below a paste, which
would harden in the cracks and between the layers, and so keep them
permanently apart, you would make them into a fair likeness of an
average mountain range--a mess--if I may make use of a plain old
word--of rocks which have, by alternate contraction and expansion,
helped in the latter case by the injection of molten lava, been
thrust about as they are in most mountain ranges.
That such a contraction and expansion goes on in the crust of the
earth is evident; for here are the palpable effects of it. And the
simplest general cause which I can give for it is this: That things
expand as they are heated, and contract as they are cooled.
Now I am not learned enough--and were I, I have not time--to enter
into the various theories which philosophers have put forward, to
account for these grand phenomena.
The most remarkable, perhaps, and the most probable, is the theory of
M. Elie de Beaumont, which is, in a few words, this:
That this earth, like all the planets, must have been once in a state
of intense heat throughout, as its mass inside is probably now.
That it must be cooling, and giving off its heat into space.
That, therefore, as it cools, its crust must contract.
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