92 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



tion of redeposited material. Erom observations made along the banks 

 of the creek it appears to be more than 20 feet thick, however. This is 

 the only lake deposit of any importance that was seen in this region. A 

 few Helices found in it crumbled very easily, showing that they have been 

 included within this drift for a long period of time. During the season 

 of high water large masses of the loose beds are washed away and 

 transported toward the north. 



DRIFT. 



The different varieties of drift that are usually found in the mountains 

 and flat country were observed within this region. Avalanchial drift 

 covers the sides of the mountains above timber-line. Frequently enor- 

 mous rock-slides extend downward for some distance, sweeping before 

 them the timber that may be in their way. In the steeper portions of 

 the main chain we found accumulations of angular rock-fi?agments that 

 evidently owe their present position to the agency of snow. Avalanches 

 starting during the season of first thaws carry along bowlders from the 

 adjacent mountain sides, which are deposited in moraine-hke arrange- 

 ment. Dependent upon the character of the rocks composing this class 

 of drift is the shape and size of the bowlder. In the higher regions of 

 the Eocky Mountains avalanchial drift represents a type of considerable 

 importance. Due to this in a great measure is the characteristic barren- 

 ness of the mountain-slopes. 



Biver drift occupies the valleys of all the streams of any size. Those 

 creeks and rivers that have any considerable drainage within the meta- 

 morphic area carry drift composed of such material with them for a long 

 distance. Some of the valleys are covered entirely with coarse drift, an 

 occurrence which is due to the parallel shifting of streams along their 

 general course. The ultimate result of gradual disintegration of river 

 drift is the production of silt and sand. Silt is not unfrequently found 

 in connection with glacial lakes. Constant diminution of the transported 

 material, more particularly of that constituting the ground moraine, re- 

 sults in the formation of this sdt. In river bottoms, and near small 

 streams, a slightly different process produces the same effects, requiring 

 more time, however. 



SOIL. 



In the lower valleys we find an abundance of soil. Along the Big 

 Popo-Agie and its immediate tributaries the soil there accumulated has 

 been utilized by settlers for agricultural purposes. Many of the lower 

 valleys might be made similarly useful, were the supply of water suffi- 

 cient for irrigation. The decomposition of shales, sandstones, and marls 

 furnishes good rich soU. ISTearer the mountains limestones enter into the 

 composition. So far as I could learn, the soil, wherever cultivated, yields 

 good crops. On some of the small creeks good bottom-lands are found, 

 containing rich soil, which may eventually become fruitful. At present, 

 grass and willow brush are the only vegetable products. 



EESUME OF THE GEOLOGY OF THE WmD EIVER EAI^GE 

 AKD THE EEGIOX EASTWAED. 



Eeconstructing the original conditions as existing in the region of the 

 Wind Eiver Eange prior to the great era of metamorphosis, we observe 

 some very interesting facts. For the reason that other portions of our 

 district, not yet described, enter into consideration in this question, a 

 complete synopsis of the former conditions cannot be now i)resented. 



