GEOLOGICAL SURVEY OF THE TERRITORIES. 15 



It #vill be seen by this analysis that the ore is very rich in metallic 

 iron, but it is supposed that it will be reduced with some difficulty. 

 Professor Silliman is of the opinion that the brown ore or limonite can 

 be employed with it, as a flux, with favorable results. Should the time 

 ever arrive when this ore is absolutly demanded by the country it will 

 be easily accessible from numerous points. 



It is probable, however, that the branch railroad from Cheyenne to 

 Montana will create a demand for these mines, and then the ore can be 

 taken down the valley of the Chugwater with ease. The Chugwater 

 Creek has its origin high up in the crest or divide of the range, and flows 

 for several miles along a rift or valley of upheaval. It then cuts through 

 a high ridge of sandstone of lower cretaceous age, and then wears its 

 channel through horizontal strata of White Elver tertiary to its junc- 

 tion with the North Platte. 



From Cache a la Poudre to the Chugwater, the Laramie Mountains pre- 

 serve a remarkable degree of regularity. The line of fracture seems to 

 have been pretty nearly north and south. The singular parallel valley, 

 previously described, ends with the "Chug," and on the north side, ex- 

 tending for four or five miles, arelofty ridges of carboniferous and triassic 

 rocks, trending nearly northeast and southwest, and dipping at a high 

 angle to the southward. From the "Chug" nearly to the Laramie Eiver, 

 these ridges are enormously developed, having almost entirely escaped 

 erosion, and the entire series of sedimentary beds to the summit of the 

 cretaceous can be studied with ease. The most conspicuous feature 

 which we notice in descending the valley is the high wall of lower cre- 

 taceous sandstone, which stretches away toward the northeast like a 

 huge wall, and the jointage is so regular that it presents the appear- 

 ance of a massive mason- work gradually falling to decay. These lower 

 cretaceous rocks, or No. 1, are composed of two beds of sandstone, in- 

 closing thin layers of clay and sand, with seams of vegetable matter or 

 impure coal. Just outside of this wall is a remnant of yellow, chalky, 

 calcareous shale, of No. 3 cretaceous, which escaped erosion when the 

 valley between it and the tertiary wall was scooped out. After the 

 Chugwater emerges from this ridge the valley becomes purely one of 

 erosion, passing through walls of whitish sandstone and marly clays, 

 the layers of sandstone projecting from the sides of the bluffs like shelves. 

 From this point to the entrance into the Laramie Eiver, the " Chug "flows 

 through the same tertiary beds, and they vary here and there in their 

 lithological composition. Near the crossing of the u Chug," where troops 

 are stationed, a hill of brown sandstone appears on the summit of the 

 bluffs, which has protected the underlying softer marls and sands. 

 The sides of these sandstone walls are forty to sixty feet perpendicular, 

 sometimes overhanging, and large masses have broken off and fallen 

 to the base. The most striking feature, however, is the tendency to 

 weather into the most picturesque castellated forms. One isolated hill 

 is circular, and the perfectly flat summit suggested for it the name of 

 " The Eound Table." 



Another isolated portion of yellow marl, still lower down, stands out 

 so conspicuously to the view of the traveler that it has received the 

 name of " The Pulpit." The marly layers indicate rather quiet waters 

 for their deposition, but the sandstones show currents of greater or less 

 velocity ; sometimes they are quite fine and easily decomposed, so that the 

 surface of the plains in the vicinity is very sandy ; then they are quite 

 coarse, forming a conglomerate, or pudding stone, mostly of small water- 

 worn pebbles, with now and then a mass six inches in diameter. They 

 also lie irregularly on the arenaceous marls below, as if the surface had 



