pkale.J INTRODUCTION DRAINAGE — PLATEAUS. 513 



three areas, corresponding to the division of the drainage, viz : The Green 

 River Drainage Area, the Snake River Drainage Area, and the Great 

 Basin Drainage Area. The first includes 5,223 square miles, the second 

 2,879 square miles, and the third 4,898 square miles. 



Green River is the artery of the first area. It probably derives the 

 largest amonnt of water from the Wind River Mountains, although a 

 large number of its tributaries rise in the mountains and hills on the 

 west side of the basin. Its course is generally south, and its tributaries 

 on the west have southerly, easterly, and southeasterly courses. On 

 the east the tributary streams are confined mainly to the extreme north- 

 eastern part of our district, there being no streams joining the Green on 

 the east between the mouth of the New Fork and that of the Big Sandy, 

 a distance of about 80 miles as the river is followed. 



The streams flowing from our district to Snake River are John Day's 

 River, Salt River, Blackfoot River, and the Portneuf River. The first 

 two of these streams are approximately parallel, flowing north and 

 joining the Snake beyond the limits of our district. The Blackfoot and 

 Portneuf Rivers are both very irregular in then courses. The general 

 direction of the Blackfoot is northwest, but some of its branches flow 

 south and southeast, and others southwest. The Portneuf at first flows 

 to the southward, approaching the bend of Bear River in a broad, open 

 valley which is continuous from the Portneuf to the Bear. It then turns 

 abruptly to the east and cuts across the Portneuf Mountains to the valley 

 of Marsh Creek, when it turns to the northward and flows in a course 

 parallel to its former one, although reversed in direction. 



Bear River, which drains the third area, has, however, the most eccen- 

 tric course. Rising in the Uintah Mountains, it flows generally north- 

 ward, entering our district a little west of meridian 111°. It then con- 

 tinues northward along the east side of the Bear River Plateau until it 

 is joined by Thomas Fork coming from the north. It then turns, and with 

 a zigzag course flows across the end of the plateau, and loses its char- 

 acter as a river in the swamp or marsh that extends northward from 

 Bear Lake. Emerging from the swamp, it continues northward and 

 northwestward to the Great Bend at Soda. Springs, where it reaches its 

 most northern point, which is 61 miles from our southern line. Flowing 

 westward through the gap at the north end of the Bear River Mountains, 

 Bear River enters the broad valley that extends northwestward to the 

 Portneuf. This valley is floored with basalt, and the river flows across 

 it in a canon that is cut some 200 or 300 feet below the surface of the 

 basalt. From the west side of the valley it takes a southerly course 

 through Gentile Valley, whence it flows by way of a canon into Cache 

 Valley. In the lowest portion of the latter it is joined by Logan Fork, 

 and turns westward through the " Gates," from which it emerges into 

 the Salt Lake Basin, and leaves our district, on its way southward to 

 Salt Lake, in longitude 112° 8', only 54- miles west of the point at which 

 it entered. It has a course of some 200 miles within the limits of our 

 district. 



Plateaus. — The district is about equally divided between mountains, 

 plateaus, and valleys. The greatest elevation is 11,490 feet in Wyoming 

 Peak in the Wyoming Range. The lowest elevation is where the Bear 

 finally leaves the district, being about 4,300 feet. The Green Rivel 

 Basin is mainly a plateau through which the streams flow in canons 

 from 100 to 400 feet in depth. The plateau slopes from the northward, 

 where its elevation is about 7,500 feet, toward the south, where it is about 

 6,900 feet. There is also a slope on the west side toward Green River 

 from the Meridian Ridge, Thompson Plateau, and the Wyoming Range. 

 33 as 



