CONTORTIONS OF ROCK-STRATA 9 



incredible. Close to one great precipice of orderly 

 horizontal layers you see the whole series suddenly 

 turned up at right angles, and the same strata which 

 were horizontal have become perpendicular. But that is 

 not the limit, for the upturned strata are seen actually to 

 turn right over, and again become horizontal in a reversed 

 order, the strata which were lowest becoming highest, and 

 the highest lowest. The rock is rolled up just as a flat 

 disc of Genoese pastry — consisting of alternate layers of 

 jam and sponge-cake — is folded on itself to form a 

 double thickness. The forces at work capable of treating 

 the solid rocks, the 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, dnd 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 measure- 

 ment from crest to hollow, protruding from the general 



