THE ROCKY MOUNTAIN REGION. 5 



ately along the Pacific coast and the narrow vallevs of some of the princi- 

 pal streams, are but trivial. The rivers descend so rapidly from the upper 

 regions that few of them are of value as highways of commerce; the valleys 

 proper are narrow: treeless plains, cold, arid table lands, and desolate 

 mountains are the principal topographic features. The more conspicuous 

 of these are the mountains; lone mountains, single ranges and great groups 

 of ranges or systems of mountains prevail. Owing to great and widely 

 spread aridity, the mountains are scantily clothed with vegetation, and the 

 indurated lithologic formations are rarely masked with soils, and the rocks, 

 as they are popularly called, are everywhere exposed; hence all these mount- 

 ains are popularly known as the Rocky Mountains. But there is more 

 than one system of mountains, and later writers wishing to be more definite 

 speak of the Cascade Mountains, the Coast ranges, the Sierra Nevada, the 

 Wasatdi Mountains, &c. But in an important sense the region is a unit; 

 it is the generally elevated region of the United States; it is the principal 

 region of the precious metals ; it is the region without important navigable 

 streams: it is the arid land of our country where irrigation is necessary to 

 successful agriculture. But above all it is the rocky region; rocks are 

 strewn along the valleys, over the plains and plateaus ; the canon walls 

 are of naked rock; long escarpments or cliffs of rock stand athwart the 

 country, and everywhere are mountains of rock. It is the Rocky Mountain 

 region. There is a necessity for popular purposes for some general name 

 and this one so appropriate will doubtless continue to be used, and it would 

 seem best not to attempt to confine its application to any more restricted 

 area ; but as our geographic and geological knowledge increases so that we 

 are able to reasonably and appropriately define distinct ranges and systems 

 of mountains within this great group, other distinctive names should be given 

 t< such ranges and grouj 



Influenced by this consideration, in speaking of the mountains that stand 

 about the Plateau Province I shall use names for certain systems which 

 seem appropriate to characterize them as distinct from other systems within 

 the #reat Rocky Mountain region. 



The eastern affluents of the Colorado River have their sources in the 

 lofty mountains that stand as walls abut the crreat parks of Southern \Vyi- 



