80 GEOLOGICAL SURVEY OF THE TERRITORIES. 



ers were derived. The valley of Cooper's Creek is a broad, nieadow-like 

 expansion, and produces a thick growth of grass, which supplies an 

 abundant provision for stock in the winter. All these streams emerge 

 from the mountains through narrow caiions. From Elk Mountain to 

 Big Laramie I doubt whether any rocks older than the cretaceous are 

 exposed on the flanks of the mountains, and these in many places are 

 obscured by heavy deposits of drift. 



The valley of the Little Laramie is now mostly occupied by ranches. 

 Thousands of cattle wander over its broad meadows and on the up- 

 land plains, and hundreds of tons of hay are prepared every year. It 

 is probable that this region is destined to become celebrated as one of 

 the finest pastoral districts in America. 



Leaving Big Laramie we ascended the western slope of the Laramie 

 range by way of Cheyenne Pass, across the cretaceous, Jurassic, and 

 triassic or red beds. The latter gives a bright brick-red appearance to 

 a wide belt along the east side of the road for 30 to 40 miles. A bed 

 of bluish limestone covers the western slope of the Laramie range with 

 remarkable uniformity, like the roof of a house, inclining 10° to 15°. 

 Underneath this, toward the summit, a bed of yellowish- white limestone 

 appears, with well-marked carboniferous fossils. Toward the summit 

 of the range we pass over a depression or valley of considerable depth, 

 which seems here to separate the changed from the unchanged rocks. 

 We then come to reddish micaceous feldspathic granites. Indeed, all 

 varieties and textures of granitic rocks occur on the summit of this 

 range. We continue to travel over ridge after ridge of metamorphic 

 rocks — some very fine in texture, others quite coarse — until we come to 

 the smooth, plain-like area which forms the central portion. This grassy 

 belt constitutes the real crest or divide, and after passing this we travel 

 over ridge after ridge of metamorphic rocks similar to those on the 

 west side, but with a reversed dip, showing a distinct anticlinal ; and 

 at the east end of the pass, at the sources of Lodge Pole Creek, the 

 metamorphic rocks rise up from beneath the red sands and limestones 

 in perfect conformity, so far as they are visible to the eye. On the 

 east slope are broken ridges, which show the carboniferous limestones 

 inclining 3° to 10°. Curiously rounded ravines, carved out of the 

 ridges by water, separate them into picturesque fragments. The road 

 through Cheyenne Pass is excellent, and is paved with crystals of feld 

 spar. The soil is fertile and the grass is good. 



South of Laramie Peak there is a great scarcity of timber on this 

 range, so that it does not deserve the name of "Black Hills," which is 

 often applied to it. 



Just south of Crow Creek there is an illustration of the granite rocks 

 carrying up the carboniferous limestones on their summits in a nearly 

 horizontal position. The tertiary beds jut up against the base of the 

 range, entirely concealing all traces of older rocks, so that larger areas 

 of older formations are broken off and lifted up far above the plains on 

 the summits of the mountains. This is not an uncommon occurrence 

 along the flanks of all the mountain ranges. It only shows how interest- 

 ing and complicated are the details of the study of these ranges, however 

 simple their structure may seem to be in the aggregate. 



Leaving Cheyenne Pass, we cross over a remarkable parallel valley, 

 or one which has been scooped out near the base of the mountains and 

 extends along parallel with it. It extends from the ridge south of the 

 drainage of Crow Creek to the Chugwater. The modern tertiary beds 

 extend down to Cheyenne, a distance of fifteen miles. 



We have now (November 1,) reached our point of departure on the 6th 



