GEOLOGICAL SURVEY OF THE TERRITORIES. 91 



matter ia tliin, shaly layers, as if composed of the broken stems and 

 leaves of plants. Above this, also, is a bed of loose, rusty-brown sand, 

 with sandstone and rusty iron-stone, and still higher up is a bed of very 

 hard siliceous rock, compact, of a lighter brown color. The inclina- 

 tion of these beds is not great, not more than from 3° to 5°. At the 

 immediate entrance of this mine the dif) is not more than 5°. The 

 coal can be easily worked and the mine well drained. The roof is simply 

 indurated clay, but this can be made firm with wooden supports. 



The coal is of the best quality, close, compact, and moderately heavy, 

 but, like most of the Tertiary coals, crumbles on exposure to the atmos- 

 phere, as is shown by the great quantities which have fallen to pieces 

 at the mouth of the mine. Even when the masses of coal have crumbled 

 in pieces some of the fragments retain the shining black color, though 

 most of it becomes a dull brown. I am inclined to regard this bed as 

 the most important one in this region, and as holding the lowest i)Osition 

 geologically. It is probably the same one that is wrought so success- 

 fully at Carbon, on the line of the Union Pacific Eailroad. 



Nearly all the land between Cooper's Creek and Eock Creek has been 

 taken possession of as coal-lands, in claims of 160 acres each. 



So far as I could determine, Eock Creek Valley is about three to five 

 miles wide, and is evidently a valley of erosion. 



On the west side there is a high ridge, plainly Tertiary, and at least 

 500 feet high, which slopes do.wn to the creek. 



In some places the strata dip 10^ or 12°, but the average dip is not 

 more than 5<^. West of Eock Creek there seems to be an unusual 

 thickness of sandstone, or loose fine sand. For ten miles or more to the 

 westward there is a large area, on both sides of the stage-road, covered 

 with massive i)iles of sandstone, most of it concretions of a rusty -brown 

 color. ' 



In these sandstones are thin layers, with a small amount of calcareous 

 matter, which have i^reserved great quantities of deciduous leaves. 

 They indicate the Tertiary age of these rocks, and also show that they 

 jut far up close to the foot-hills of the mountains. 



These massive sandstones give a very rugged aspect to the surfiice 

 of this region. 



The Tertiary strata are very heavy, varying from 1,500 to 2,000 feet in 

 thickness in the aggregate, and composed mostly of alternate beds of 

 rusty-yellow sandstone, and greenish-gray indurated sands and clays. 

 All the beds incline slightly from the mountains about northeast. 



From Laramie Eiver to the Medicine Bow we see no indication of the 

 red beds, though they must exist higher up in the mountains. 



On the south side of our road the slopes are very gentle, the hills 

 rising up gradually like steps, and all the elevations, and even the 

 gorges through which the little streams flow down from the mountains, 

 are so covered with debris that all their rough points are smoothed off, 

 and so covered with grass that it is difficult to find the basis rocks. 



Even Elk Mountain, which must rise at least 1,500 feet above the bed 

 of the medicine Bow at the stage-station, has been so smoothed down by 

 drift action, and now covered with grass, that the rocks cannot well be 

 seen. 



IS'orth of the road the Tertiary rocks made very ragged " bad lauds," 

 and the bare surface and conical hills give to this district the same 

 gloomy bareness but picturesque appearance of the country occupied by 

 the same formations on the Upper Missouri. 



On the night of September 4 we camped on Medicine Bow Eiver, 



