56 GEOLOGICAL SURVEY OF THE TERRITORIES. 



made their appearance for a short distance in the bluffs. The divide be- 

 tween the drainage of Smith's Fork and Henry's Fork, is. a high ridge of the 

 leaden-brown clays of the Bridger group, which extends up and juts 

 against the base of the Uinta Mountains. Passing over this divide we 

 descended quickly to the valley of Henry's Fork, and camped near the 

 point where it issues from the foot-hills of the Uinta Mountains, 29 

 miles southwest of Fort Bridger. This is a beautiful valley, quite broad, 

 a large portion being meadow, and the surrounding hills, especially on 

 the south side, covered with grass, rendering it a favorite place for years 

 past for procuring hay and grazing stock. Hundreds of tons of hay 

 have been cut and cured for winter use in this valley the present year. 

 The time cannot be far distant when it will be occupied by settlers from 

 its mouth nearly to its source. The view of the Uinta range from our 

 camp was as beautiful and inviting as from Fort Bridger. 



On the morning of the 2d I started up the valley with a small pack- 

 train. The geology did not differ materially from that of the portions of 

 the range already described. Up among the foot-hills is an isolated butte 

 about three hundred feet high, capped with the brown clays of the Bridger 

 group passing down into the calcareous layers of what I have termed 

 Green Eiver beds, containing an abundance of turtle shells, with teeth, 

 j aw s, and vertebra of some extinct mammal. These chalky limestones are 

 also filled with large Planorbis in a perfect state of preservation. These 

 beds along the flanks of the mountains have been slightly elevated or 

 carried up in the later stages of the elevation of the range. They 

 usually incline about 3° to 5°. The radiating ridge on the north side of 

 the valley is covered with land-slides, which show a heavy deposit of 

 reddish clays with narrow whitish bands, evidently a modern deposit, 

 pliocene or quarternary overlapping the well-defined tertiary beds. 

 These extend up a few miles and are again overlapped with the drift 

 deposit described in the preceding chapters ; the same dense groves of 

 pines and aspens, the same open meadows, deep ravines, fallen timber, and 

 great quantities of rocks on the surface occur, rendering traveling exceed- 

 ingly difficult, which we have before noted. We passed the ridge of lime- 

 stone into the belt of sandstone, with the lofty piles of debris, gradually 

 ascending to the banks of perpetual snow, where the pines dwindle down 

 and trail upon the ground. We rode our horses up to a point above the 

 limits of arborescent vegetation, toward them, to a point 12,265 feet above 

 the sea, and ascended to the summit of Gilbert's Peak. 



We camped the night of the 3d in a beautiful open meadow, at the 

 sources of one of the branches of Henry's Fork, 9,833 feet. The lime- 

 stone or continuation of Photograph Bidge was 9,986 feet, while the 

 valley between the carboniferous limestone ridge and the inner purplish 

 sandstone ridge was found to be 9,453 feet. We found that the extreme 

 limit of tree vegetation was higher here than farther west, 11,106 feet; 

 and the point where the upright trees break off rather abruptly was 

 about two hundred feet lower. As a general rule the trees dwindle in 

 height to about twenty or thirty feet and then fall off abruptly to the 

 trailing form, which usually extends up two hundred or three hundred 

 feet higher in straggling bunches or groups. From the summit of Gil- 

 bert's Peak with my excellent field-glass I could look far over the surround- 

 _ng country and study the principal geological and geographical features 

 in their relations to each other. There are three main branches of 

 Henry's Fork that rise in the axis of the range. The east branch has 

 its source at the base of Gilbert's Peak on the northeast side and flows 

 nearly north for ten or fifteen miles. The middle branch rises on the 

 south side of the peak, flows west for a short distance, and bends around 



