VI MOUNTAINS 215 



are no mere accidents, but that for every 

 mountain chain, for every peak and valley, 

 there is a cause and an explanation. 



The origin of Mountains is a question of 

 much interest. The building up of Volcanoes 

 is even now going on before our eyes. Some 

 others, the Dolomites for instance, have been 

 regarded by Richthofen and other geologists 

 as ancient coral islands. The long lines of 

 escarpment which often stretch for miles across 

 country, are now ascertained, mainly through 

 the researches of Whitaker, to be due to the 

 differential action of aerial causes. The gen- 

 eral origin of mountain chains, however, was 

 at first naturally enough attributed to direct 

 upward pressure from below. To attribute 

 them in any way to subsidence seems almost 

 a paradox, and yet it appears to -be now well 

 established that the general cause is lateral 

 compression, due to contraction of the under- 

 lying mass. The earth, we know, has been 

 gradually cooling, and as it contracted in doing 

 so, the strata of the crust would necessarily be 

 thrown into folds. When an apple dries and 

 shrivels in winter, the surface becomes covered 



