93 DESCRIPTIVE GEOLOGY. 



Littlie Laramie River, end in small lakes or ponds, or else are lost in the 

 sands before reaching the main river. On the opposite side of the range, 

 six good-sized streams drain the waters into the North Platte River. Com- 

 mencing from the south, they occur in the following order: Douglas, French, 

 Brush, Cedar, Cottonwood, and Pass Creeks. On the east side of the Medi- 

 cine Peak group, the waters, restrained from flowing eastward, drain north 

 by the Medicine Bow River and Rock Creek; both streams, after a circuitous 

 course through the sedimentary strata, emptying into the North Platte beyond 

 the limits of our map. 



On the southeast side of Medicine Peak, however, the creeks run toward 

 the Little Laramie River, which, as already mentioned, cuts the eastern 

 ridge. Elk Mountain, a comparatively small mass, standing isolated, 

 sends out no large stream, but numerous small creeks, which empty into 

 the Medicine Bow River on the one side, and Pass Creek on the other. 

 Thus, it will be seen that of the leading river features of the Rocky Mount- 

 ain system, the North Platte, and the Laramie, which, however, ultimately 

 falls into the North Platte, drain almost the entire area of the Medicine Bow 

 Range; that but a small proportion of the water seeks the South Platte, and 

 an equally small amount is added to the Grand River. 



All the higher regions exhibit well-marked evidences of glacial action. 

 The summits of the main peaks are everywhere worn in a manner which 

 shows unmistakable signs of ice erosion, and glacial boulders and detrital 

 matter cover the lesser depressions and slopes. The valleys of Grand 

 River, and the branch of the Cache la Poudre, which -comes down from 

 Mount Richthofen, are both examples of g-laciallj^-carved basins. At their 

 upper ends, they are both somewhat similar in outline; but below, the 

 Grand descends more rapidly, receives numerous tributaries, and the glacial 

 phenomena are on a more extensive scale. Opposite Mount Clark, the 

 Cache la Poudre receives a small tributary from the main peak, and near 

 their junction is a fine glacial lake. From Mount Clark also descended the 

 glacier of the Upper Laramie Valley, while on the south side short but 

 deep trough-shaped canons extend down to the North Park. 



In the region "of Medicine Peak, glaciers occupied all the upper val- 

 leys, and the amphitheatres, witli mural faces 1,500 feet deep, cut out of 



