he
foundations of the great mountains, in this way are gigantic beyond
measurement. This folding of the earth's crust is caused by the fact
that the "crust," or skin of the earth, has ceased to cool, being
warmed by the sun, and therefore does not shrink, whilst the great
white-hot mass within (in comparison with which the twenty-mile-thick
crust is a mere film) continually loses heat, and shrinks definitely
in volume as its temperature sinks. The crust or jacket of stratified
rock deposited by the action of the waters on the surface of the globe
has been compelled--at whatever cost, so to speak--to fit itself to
the diminishing "core" on which it lies. Slowly, but steadily, this
"settlement" has gone on, and is going on. The horizontal rock layers,
being now too great in length and breadth, adjust themselves by
"buckling"--just as a too large, ill-fitting dress does--and the Alps,
the Himalayas, and other great mountain ranges, are regions where this
"buckling" process has for countless ages proceeded, slowly but
surely. Probably the "buckling" has proceeded to a large extent
without sudden movement, but with a lateral pressure of such power as
ultimately to throw a crust of thousands of feet thickness into deep
folds a mile or so in vertical measurement from crest to hollow,
protruding from the general level both upwards and downwards, whilst
often the folds are rolled over on to each other.

[Illustration: Fig. 3.--Diagrams to show the "folding" of rock strata.
A. Normal horizontal position of the strata, _a_, _b_, _c_, _d_; _xy_,
horizontal line. B. Folding due to a shortening of the horizontal _xy_
by lateral pressure, acting in the direction of the arrow and due to
shrinkage. C. More extreme case of folding, in which a raised ridge is
made to fall over so as to bring the lowest layer _d_ above _a_, _b_
and _c_.]

This crumbling and folding has gone on at great depths--that is to
say, some miles below the surface (a mere nothing compared with the
8,000 miles diameter of the globe itself), though we now see the
results exposed, like the pastry folded by a cook. Immense time has
been taken in the process. A folding movement involving a vertical
rise of an inch in ten years would not be noticed by human onlookers,
but in 600,000 years this would give you a vertical displacement of
more than 5,000 ft. (nearly a mile!). It has been shown that in
Switzerland, along a line of country extending from Basle to Milan,
stra