54 



Korth Platte iu North Park, Colorado, tlie two rivers flowing eastward 

 aud uniting in Nebraska. 



At the northwest the Big Horn, Yellowstone, aud Upper Missouri 

 Rivers rise within or near the Yellowstone Park, and find outlet 

 through the channel of the Missouri. Crossing the Continental Divide 

 westward, it is found that Clark's Pork of the Columbia, the Salmon 

 Eiver, and Lewis or Snake Eiver, also rise iu the same region, but, as 

 tributaries of the Columbia, send their waters to the Pacific Ocean. 



In the southwest the principal streams flowing into the lakes of the 

 Great Salt Lake Basin are the Bear, Weber, and Sevier. The Green 

 Eiver, which has its source iu the Wind Eiver Mountains, Wyoming 5 

 the Grand Eiver, which drains Middle Park, Colorado, and the San 

 Juan Eiver, which rises in the southern part of the same State, unite 

 in southern Utah and form the Colorado Eiver of the West. 



The Eio Grande and Arkansas Eivers drain the southeastern portion 

 of the Eocky Mountain region. They have a common origin in the 

 mountains of Colorado, but the first seeks an outlet directly in the Gulf 

 of Mexico, while the latter, at a point some 800 miles northeastward, 

 unites with the Mississippi river. 



Tlie Eio Grande, Arkansas, North and South Platte, and their main 

 afiliients, debouch upon high planes which slope rapidly to tlie south and 

 east; and while the most of these streams pass through deep canyons 

 in emerging from the mountains, they flow with a rapid current (de- 

 scending from 5 to 8 feet to the mile) in shallow channels. Therefore 

 it is not difficult to utilize their waters for irrigation and other pur- 

 poses. 



In Montana the plains have much less elevation than in the region 

 southward, and the principal streams, the Upper Missouri and tlie Yel- 

 lowstone, following a long and devious course to the j auction of the 

 two, have a gradual descent and sluggish flow ; hence it is not easy to 

 bring their waters to the level of the adjacent country. What can be 

 done there by a system 01 reservoirs which will save the flood waters of 

 spring and early summer, is a question for the future. 



In Idaho, upon the western slope of the range, the principal streams 

 flow rapidly^ through arable valleys, and the waters can be easily util- 

 ized. 



Southward, in western Colorado, the streams, in descending from the 

 mountains, have a swift current and pass through valleys of much nat- 

 ural fertility. As they approach the plateau region, farther south and 

 west, some of them enter profound canyons, and thus are lost for irri- 

 gating purposes. 



ALTITUDES. 



The altitudes of the Eocky Mountain region, inclusive of the valleys, 

 plains, and plateaus, vary from 680 feet above sea level at Lewiston, 

 Idaho, to an extreme height of 14,460 feet in the mountains of Colorado. 



