THE HARDENING OF ROCKS 



the land ; the heavier parts must always roll towards the 

 lighter. The action would be as resistless as the slow 

 moving onward motion of those masses of ice called 

 glaciers ; or as the movement of the great ice plains in 

 Greenland; or of those ice plains which in Antarctic 

 regions are always spreading towards the sea. 



There are two views of it. There is the outward 

 pressure of the regions where the sediments of rock are 

 being laid down. There is the inward pressure towards 

 the regions which have lost soil. Sometimes these two 

 actions may conspire. A region where great denudation 

 is taking place may send its waste material towards the 

 sea, where it is deposited near the coast and not far 

 from the highlands or mountains or plateaux which 

 founded the soil. The shallows near the shore become 

 a belt which is being loaded ; the big mountains near 

 by are a belt which is unloading; and thus there are 

 two strains set up together. It is not hard to see the 

 enormous crumpling effect which this would produce on 

 the lower strata one or two miles beneath the surface 

 of the sea and three or four miles below the topmost 

 crests of the mountains. These are circumstances which 

 may not be common ; but the reader will find a quite 

 sufficient explanation of some of the crumpling, and 

 many of the changes in composition and appearance of 

 the deep -sunk rocks, if he remembers the great pres- 

 sure over them, and the fact that the high regions may 

 be supposed always to have a tendency to slip towards 

 the lowlands. 



J36 



