GEOLOGICAL SURVEY OF THE TERRITORIES. So 



of it were seen (on the high divide west) about the rim of the valley. 

 The granites form the boldest and most barren-looking ridges I have 

 ever seen ; some of the peaks are true dome-shaped, and are apparently 

 as smooth and as bare as a church dome. No water is to be found in 

 or around them, and here and there a few stunted pines manage to ex- 

 tract a scanty nourishment from among the fissures. On our left the 

 most magnificent benches extend down from the Seminole Mountains 

 for ten miles or more. This range is smoothed and grassed over, and 

 some portions are thickly covered with pines. 



West of the Seminole Mountains is another detached range or group 

 of hills ten to fifteen miles long, parallel with the . Sweetwater ; then 

 near the Three Crossings there is another range, low and covered thickly 

 with pines. Still farther west is another detached group of hills, which 

 extend to the South Pass. These hills undoubtedly form the southern 

 rim of the Sweetwater basin. T think this basin varies from thirty to 

 fifty miles in width. In one of these detached groups of hills we can 

 see a high ridge of limestone, with a strike northwest and southeast, 

 while the group of hills trends about northeast and southwest. Near 

 the Three Crossings the high granite ridges are on our right, and rise 

 seven hundred to eight hundred feet above the bed of the Sweetwater. 

 From the tops of the ridges, far to the westward, we can see the Wind Eiver 

 range, and feel the cool breeze that comes sweeping down the valley, la- 

 dened with the icy chill from the snow-clad summits. Small lakes are also 

 visible in the plains, some of which seem to be fresh water, while all around 

 5 the shores of others there is a thick efflorescence like snow. Far dis- 

 tant to the north and northwest there is another rim of this basin, which 

 I have called the north rim or side. The granites near the Three Cross- 

 ings seem to be somewhat peculiar. There are two principal sets of 

 joints, one of which is horizontal and the other vertical, dividing the 

 granite range into cubical blocks, and giving to the sides of the ridges 

 somewhat the appearance of mason work. Sometimes the very compact 

 feldspathic beds separate into columnar forms, which are quite pic- 

 turesque. The peculiar mason-like appearance of the granite valley is 

 entirely due to the vertical and horizontal fissures. This feature is more 

 marked at this locality than at any other point we have examined. 



On the 31st we made an examination of the lower range of hills which 

 extend up to the South Pass on the south side of the Sweetwater. We 

 found the granites occupying a very restricted area, and inclining from 

 them a larger thickness of Potsdam sandstone with Obolella nana and 

 aLingula. Inclining against the Silurian sandstone was a massive bed 

 of compact bluish and yellow limestone, with a strike northeast and 

 southwest. At one locality I found the beds had been tipped past ver- 

 tically 20°. The red beds were also shown here quifte well developed. 

 It would seem that the range of hills on the south side of the Sweet- 

 water valley forms one side of the anticlinal, and the axis of elevation 

 is not far from the channel of the stream. A pretty little branch with 

 a considerable volume of water, and crowded with beaver dams, has 

 excavated a valley near this point. It has a fork also, which is fringed 

 with little cotton woods, a feature quite unusual in the Sweetwater valley. 

 Jutting up against the sides, and penetrating every valley or gorge in 

 the outline of the mountains, are the brown indurated sands of the Wind 

 Eiver deposits; among them are impure seams of lignite or carbon- 

 aceous clay, with layers of coarse "sandstone or an aggregate of particles 

 of quartz. The disintegration of the harder beds has covered the sur- 

 face with small fragments of rock. A little farther to the southward a 

 huge hill, with almost vertical sides, is composed of light g^ay ands 

 3g 



