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, strata of 10,000 ft. to 20,000 ft. in thickness, which, if straightened out, would give a flat area of that thickness, and of 200 miles in length, have been buckled and folded so as to occupy only a length of 130 miles! The former tight-fitting skin of horizontal rock layers has "had to" buckle to that extent here (and in the same way in other mountain ranges in other parts of the world), because the whole terrestrial sphere has shrunk, owing to the gradual cooling of the mass, whilst the crust has not shrunk, not having lost heat.