GENERAL FEATURES OF THE EARTH. 



19 



1:1 



Fig. 10. 



(b.) Composition of mountain-chains. — (1.) Mountain-chains have 

 been stated to include several mountain-ridges ; and even the ridges 

 often consist of subordinate parts sim- 

 ilar in arrangement. In the great 

 chain of western North America, — the 

 Rocky Mountains, — about the summit 



. 2 : o 



there are, in general, two prominent 

 ranges ; then, west of the summit, l : 2 

 within 100 to 150 miles of the coast, 

 there is the Washington Range, in- * " " 

 eluding the Cascade of Oregon and the 1 '. 5 

 Sierra Nevada of California, each with l : 6 

 peaks over 14,000 feet in height: 

 between this range and the summit there are in many parts several 

 ridges more or less important ; and between it and the coast other 

 ridges make up what has been called the Coast Range. The Appa- 

 lachians also, although but a small chain, consist of a series of nearly 

 parallel ridges. In Virginia there are, beginning at the east, the Blue 

 Ridge, the Shenandoah Ridge, and the Alleghany, besides others inter- 

 mediate. 



(2.) The ridges of a chain vary along its course. After continuing 

 for a distance, they may gradually become lower and disappear ; and 

 while one is disappearing another may rise to the right or left ; or 

 the mountain may for scores of leagues be only a plateau without a 

 high ridge, and then new ranges of elevations appear. The Rocky 

 Mountains exemplify well this common characteristic, as is seen on 

 any of the recent maps. The Sierra Nevada dies out where the Cas- 

 cade Range begins ; and each has minor examples of the same princi- 

 ple. The Andes are like the Rocky Mountains ; only the parts are 

 pressed into narrower compass, and the crest ranges are hence con- 



li 



Figs. 11 to 16. 



12 



13 



hi,. 



14 



15 



tinuous for longer distances. The Appalachian ridges are rising and 

 sinking along the course of the chain. The high land of the south- 

 west terminates in New York ; and just east stands the separate line 



