naturally enough, how such a heap of beds as
I have described can take the shape of mountains like Snowdon.

Look at any sea cliff in which the strata are twisted and set on
slope. There are hundreds of such in these isles. The beds must
have been at one time straight and horizontal. But it is equally
clear that they have been folded by being squeezed laterally. At
least, that is the simplest explanation, as may be proved by
experiment. Take a number of pieces of cloth, or any such stuff; lay
them on each other and then squeeze them together at each end. They
will arrange themselves in folds, just as the beds of the cliff have
done. And if, instead of cloth, you take some more brittle matter,
you will find that, as you squeeze on, these folds will tend to snap
at the points of greatest tension or stretching, which will be of
course at the anticlinal and synclinal lines--in plain English, the
tops and bottoms of the folds. Thus cracks will be formed; and if
the pressure goes on, the ends of the layers will shift against each
other in the line of those cracks, forming faults like those so
common in rocks.

But again, suppose that instead of squeezing these broken and folded
lines together any more, you took off the pressure right and left,
and pressed them upwards from below, by a mimic earthquake. 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, lik