GEOLOGICAL SURVEY OF THE TERRITORIES. 113 



detail in order that its beauty and regularity may be understood ; and 

 altkoguh I regard it, as well as the Black Hills of Dakota, a more perfect 

 illustration of my tkeory of tke elevation of tke Eocky Mountain system , 

 yet it is not as conspicuous an example to tke casual observer as lie lofty 

 ranges west of Denver. 



From Ckeyenne to Granite Canon, near tke summit of tke first range, 

 tke grade of ascent is greater than between any other points along the 

 Union Pacific Eailroad. The distance is about nineteen miles, and the 

 difference of elevation between the two places is one thousand eight 

 hundred and sixty-seven feet, or a grade of more than ninety feet per 

 mile. The recent tertiary beds lie close up to the flanks of the moun- 

 tains, over a belt of several miles, affording accomparatively easy transi- 

 tion from the newer formations to the granite nucleus. 



For hundreds of miles either north or south of this line it would 

 be difficult or perhaps impossible to build a railroad across the 

 mountains, but here nature seems to have provided an easy inclined 

 plain to the very margin of the mountain summit. The ridges are very 

 nearly concealed, while on either side they can be seen as formidable 

 as anywhere along the eastern base. 



Close up to the sides of the mountains this more recent formation is 

 composed of water-worn boulders and pebbles, varying much in size, 

 but as we recede eastward toward the plain they disappear for the 

 most part. The same is the case with the drift, which shows clearly 

 that the causes which led to the deposition of these beds operated in the 

 vicinity, and the materials are derived from the mountains near by. 



On either side of this inclined plain, north or south, we can see the 

 upturned edges of the different sedimentary rocks in tkis region. 

 Between Granite Canon and Cacke la Poudre, about forty miles along 

 the foot of tke mountains, not only is tke scenery rugged and grand to 

 the eye, but tke complications of geological structure are very interest- 

 ing. Tkere seems kere to kave been a jog in tke minor ranges which, 

 compose the aggregate range, and several of these smaller ones disap- 

 pear in the plains. The belt of upheaved ridges is here ten to fifteen 

 miles wide, revealing all the sedimentary rocks, from tke carboniferous 

 limestones to tke most recent tertiary beds. Tke peculiar brick-red 

 color of tke sandstones, wkick are supposed to be of tke triassic age, 

 gives a singular appearance to tke scenery. We kave kere tke carbon- 

 iferous limestones resting upon tke granites ; tken a series of brick-red. 

 sandstones inclining at different angles, witk beautiful grassy valleys, 

 between tke ridges, and little streams cutting through nearly at right 

 angles; then a thin group of sand and marls, which may be Jurassic; 

 then the whole series of cretaceous beds with their characteristic 

 remains; then the lignite tertiary beds with coal, all conforming to each, 

 other, and all inclining from the mountains at different angles. All the 

 beds just alluded to perfectly conform to each other, but the light-colored 

 rocks, which most attract the eye of the traveler at Cheyenne, do not 

 conform, and were of course deposited subsequent to the uplifting of 

 the mountain ranges. We can see, therefore, that the eastern flanks of 

 these mountains formed a shore line for a great fresh-water lake. 



If we make our investigations still nortk of tkis line, we skall find, for 

 two kundred miles or more, tkattkese recent beds jut up against tke older 

 sedimentary beds, and in many places rest upon tke granites. Sometimes 

 tke wkitisk rocks kave been removed by erosion, so as to expose tke 

 older ones, but near Laramie Peak tkey entirely conceal all but tke 

 granites. In many places tkese recent beds are found kigk up on tke 

 flanks of tke mountains, in a nearly korizontal position, as if many of 

 8 g 



