,9o8.| THE PHYSICS OF THE EARTH. 247 



" Thus, then, there are two types of mountains strongly contrasted, 

 mountains of the one type are formed by lateral pressure and crushing, of 

 the other type by lateral tension and strctehing. The one gives rise mainly 

 to reverse faults, the other always to normal faults. Alountains of the one 

 type are formed by upswelling of thick sediments, those of the other type 

 by irregular readjustment of crust-blocks. Mountains of the one type are 

 born of the sea, those of the other type are born on the land. We find 

 examples of the one type in nearly all the greatest mountains everywhere, but 

 especially in the Appalachian, the Alps and the Coast Range. The best 

 examples, perhaps the only examples, of the other type are the Basin ranges. 

 Some mountains, as the Sierra, the Wahsatch, and certainly some of the 

 Basin ranges, belong to both types. In their origin, they have formed in 

 the first way, but afterward have been modified by the second way. Thus 

 the first is the fundamental method, and the second only a modifying proc- 

 ess " (p. 277). 



These views of Leconte call for no special comment, beyond the 

 remark that normal fatilting itself is wholly tinexplained. If secti- 

 lar cooling were the catise, such fattlts otight to occur east of the 

 Rocky Motmtains as well as west of them. The important differ- 

 ence is that the Pacific Ocean was on the west pttshing up the land, 

 and a continental basin on the east, either dry or covered by shallow 

 water and therefore doing little or no pushing at all. In any case 

 the great plateaus of the west were certainly uplifted by the Pacific, 

 through the expulsion of lava under the land. In the Andes of 

 South America the plateaus are higher indeed, but also narrower 

 than those in North America, because in our continent the relief 

 resulting from the leakage of the ocean took a broader and less ele- 

 vated form. It is impossible for any one to dotibt the identity of 

 the forces which raised the Andes and their plateaus, the Himalayas 

 and their plateaus, and the Rocky [Mountains and the mountains and 

 plateaus of the Great Basin. The principle of continuity shows 

 clearly that the cause was everywhere one and the same. Several 

 American geologists have suggested vertical uplifts in the Great 

 Basin, from the way in which the crtist blocks are displaced ; but 

 heretofore no known cause for such movements could be assigned, 

 because it was held that secular cooling is the chief if not the onlv 

 cause operating in the development of the globe. 



§ 43. Viezi's of Rev. 0. Fisher. — The Rev. O. Fisher was the 

 first to show by long and patient research the total inadequacy of 

 secular cooling to account for the observed height of mountains. 



