enduch.] EAST OF WIND EIVEE EANGE CAEBONIFEEOUS. 77 



composed of white and light yellow quartzitic rocks. Descending either 

 east or west, we observe that these are overlaid, first, by magnesian 

 limestones, unchanged, and then by massive beds of blue limestone. 

 \Te have, in this instance, a protrusion of Subcarboniferous rocks along 

 a definite anticlinal axis. Near the central fine of upheaval, we find 

 them thoroughly metamorphosed. Toward the north they are soon 

 hidden from sight under the heavy limestone strata. Following the 

 outcrop southward, we find that the axis of the fold turns in a south- 

 westerly direction, exposing the older series on high points. Occasion- 

 ally a canon is cut down deeply through the Carboniferous limestones, 

 and there again we see the Subcarboniferous strata. The white and 

 yellow quartzites of the region are evidently the metamorphosed calca- 

 reous sandstones which have been mentioned in previous pages. Ap- 

 proaching the northern edge of the Sweetwater group while following 

 the anticlinal axis,, we find that not only Subcarboniferous beds he ex- 

 posed, but that Potsdam sandstone and granite make their appearance. 

 A few strata above the former might be referred to the Calciferous series, 

 but they are very insignificant. Necessarily the area of these older 

 rocks is a restricted one, as the dips on either side of the axis of upheaval 

 are very steep. Younger groups, leaning directly up against the former, 

 render then outcrops quite narrow. 



Carboniferous. 



Conformable in every respect with the Subcarboniferous group are 

 the limestones belonging to this series. In their general arrangement, 

 as well as hi then detail features, they show no variation from the char- 

 acter as exhibited by the same group farther west. After they have 

 disappeared from the surface for some distance, we first find them again 

 forming the slopes of Sheep Mountain. Here, as elsewhere, the thickness 

 of these massive limestones amounts to about 2,000 to 2,200 feet. Near 

 the northern base of the mountain they sink out of sight, but continue 

 for some distance on the southern side. Forming there the narrow, 

 walled canon of Beaver Creek, they extend south and southwest toward 

 the northern edge of the Sweetwater group. In their course they follow 

 the anticlinal axis of this region. Owing to a diminishing dip, both 

 toward the east and west, they are exposed over a considerable area. 

 So far as I could determine, no unbroken surface-connection exists be- 

 tween these Carboniferous beds and those of the third chain, so long as 

 both remain within the area of Wind Eiver drainage. 



On the south side of Beaver Creek a very interesting series of springs 

 was noticed in the Carboniferous limestones. A gentle slope leads north- 

 ward toward the stream from the higher hills along the anticlinal axis. In 

 the limestones of this slope we observe a vertical opening. It has the 

 form of an ellipse, is about 200 feet long, 150 wide, and 120 deep. Some 

 process, whereby a cave of corresponding proportions had been excavated, 

 had rendered the roof-rock unsafe until it fell down. The walls of the 

 "hole" are perpendicular, and show the influence of chemical action. 

 A short distance downward from this opening there is a hot sulphur 

 spring. It bubbles up out of the rocks through a deposit of fine sand 

 and some gravel, emitting large quantities of sulphuretted hydrogen gas. 

 The temperature of the water is 06° F. A few hundred yards below we 

 find another spring, containing the same kind of water, but ice-cold. On 

 the bottom of the hot spring the pebbles, when taken from it, show a 

 thin gold-colored coating. This is very uniformly spread over them, is 

 bright, and is composed of pyrrhotite, nearly simple sulphide of iron. 



