254 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



stream descends about 30 feet iu about 200. About two miles below 

 this we began to find outcrops of a iine-grained, ferruginoas, laminated 

 sandstoue, destitute of fossils, but probably of Tertiary age. Some of 

 the layers showed abundant ripple-marks. At the falls, the rock is 

 heavy-bedded. The dips are mostly about 22°, varying somewhat on 

 either side of due east. Just above the falls, and opiDosite to our camp, 

 four thin layers of coal, varying from 1 inch to 6 inches in thickness, and 

 two layers of clay ironstone, (iron carbonate,) varying from 6 inches to 

 1 foot in thickness, are all included within 10 feet of shales. About 

 three miles above this point, the caiiou opens out into a broad valley, 

 with rather narrow bottoms, but with broad, gentle, grassy slopes, 

 topped with gently-rounded hills, partly timbered, partly grassy. The 

 huge rocks which lower down had encumbered both bottoms and slopes 

 gave place to cobble-stones, j)ebbles, and sand. From this point Captain 

 Barlow turned eastward, in 1871, after following up the caiion, as we 

 had now done; and here we turned eastward to climb the hills. From 

 a higher point, we saw that the rest of the valley is mainly a broad 

 basin. There appears to be no pond at the head of the stream, which 

 is apparently near the summit of a flat divide, from the other side of 

 which the waters run to Buffalo Fork. This is mostly fine grazing- 

 groand, and the numerous game-trailsgiveevidence that it is frequented 

 by deer and elk ; indeed, we found two herds of elk, of about twenty 

 each, among the groves on the top of the ridge. The mountains shut 

 off the winds on all sides, and the valley lies so well to the sun that 

 the snows must melt rapidly here, thus causing the great freshets of 

 which the broad, gravelly bottom of the river below had already given 

 so abundant evidence. The upper slopes of the ridge on either side are 

 mostly bare of timber, and many parts of them are badly washed. 

 Those on the east are composed of mostly thin-bedded sandstones, 

 probably of Tertiary age, at least 2,000 feet thick, with variable south- 

 easterly dips. A few red hiyers appear, but the majority of them are 

 gray. No fossils were found, though careful search was made for them. 



From the summit of this ridge, we again saw Yellowstone and Heart 

 Lakes, and had a fine view of the rugged Tertiary (?) crests of the Big 

 Horn Mountains to the east, running down to Union Pass. 



The scattered groves of spruces, with occasional pines, which are so 

 constantly characteristic of the upper edge of the timber, occur scat- 

 tered over these upper slopes, and nearly every cluster contains some 

 young trees ; but we nowhere encounter the patches of dense young 

 growth which at a lower level so constantly start up, in" a short time, 

 whenever a body of old timber has been burned over and has fallen, 

 and often even before the dead trees have fallen. The idea has been 

 advanced that the burned patches are not thus renewed in these mount- 

 ains; i{\i(\^ under some circumstances^ this seems to be true; but the r^iZe 

 is just the opposite, as those of us who have had occasion to penetrate the 

 vigorous growth of this dense young pine, whether alone or with a j^ack- 

 train, will most vividly remember while memory lasts. 



Crossing this ridge, we came to the valley of a stream which we after- 

 ward ascertained to be the head of the main stream of Snake Eiver. | 

 At its upper extremity we found a flat valley-divide, upon which are 

 two small i>ODds, near together, covering from eight to ten acres each, ' 

 one of which is the ultimate source of Snake Eiver, while the flow from 

 the other joins Buffalo Fork, and so reaches the Snake just below 

 Jackson's Lake. Ascending the high, sharp ridge on the west side of 

 this valley, at least 500 feet high, we find its slopes to consist entirely 

 of large and small well-rounded pebbles of variously-colored quartzites, 



