GEOLOGICAL SURVEY OF THE TEEEITORIES. 257 



tumbling masses of rock, but apparently without any accumulation of 

 gravel. Considerable rapids occur through nearly the whole caiion, and 

 one fall of nearly 50 feet was noticed. The caiion deepens rapidly to 

 from 7U0 to 800 feet, with widths of less than half the depths at the 

 deepest precipitous portions, though in some places widening above, so 

 as to hav^e sloping banks of about 50° from the horizon. About three 

 miles down, it reaches its culmination, and is truly grand. It has none 

 of the brilliancy of coloring so characteristic of the Yellowstone Caiion, 

 but the somber tints of its gray, brown, and dark-red lichen-covered 

 rocks, occasionally variegated with smaller patches of green and yellow, 

 constitute a peculiar style of beauty and add greatly to the effect of its 

 narrow dark depths. The only deficiency is in the supply of water, 

 which is small at this season. The rocks are all volcanic, mostly por- 

 phyries and trachytes, with some porphyritic obsidian. Some two miles 

 below the end of the main caiion, the cliffs close in again to the river, 

 for a few hundred feet, to a width of about 200 feet, with a height of 

 400 feet or more, forming a suitable gateway to the caiion from below. 

 The valley below this is still narrow, but opens enough to give room 

 for a few beaver-dams in its swampy bayou-banks before it rushes out 

 into the valley of the Snake. 



The high ridges which form the slopes about Lake Lewis bear back 

 from the river and form no part of its lofty caiion-walls. Between the 

 river and this upper slope, on the west side, a large stream gathers 

 its waters from the abundant springs of the mountains and occupies a 

 broad flat valley on the lower level, filled with beaver-dams, whence it 

 lushes, through a narrow, winding caiion and over a 30-foot fall, to meet 

 the river about a mile above its junction with the Snake. On the foot- 

 slopes of the roountain, along the west side of the beaver-dam flat, 

 there are considerable numbers of warm springs oozing out, and con- 

 siderable accumulations of siliceous deposits are indicated by the soil. 

 A small run, formed from a number of these springs, gave a tempera- 

 ture of 101°. It is possible that active springs of some size exist in 

 this neighborhood, but the contrary is indicated by the extensive bodies 

 of dense timber, which also hinder exploration. From the south end of 

 the cluster of beaver-dams aforesaid, a stream flows southward, which 

 attains a pretty good size before it joins the Snake, about three miles 

 below the camp at the forks. Its source is jirobably in strong springs 

 on the flat divide, which have been dammed up by the beavers so higli 

 that the ponded waters can escape in both directions. 



The mountain which bears oft' westward from the head of the caiion 

 forms the steep northern w^all, while the extreme slopes of the Teton 

 Eange form the more gently-sloping southern boundary of a flat valley, 

 from five to eight miles wide, which breaks through to the basin of Hen- 

 ry's Fork, and is occupied by the sources and main stream of Falls 

 Eiver. The extreme source of this river is in the great water shed of the 

 northern mountain, from whose southern face it bursts in four immense 

 springs, which leap from its steep rocky sides as full-grown streams, 

 and rush in beautiful cascades, from 75 to 100 feet high, down a slope 

 of about 40°, to form two large branches, which, a mile below, unite in a 

 stream carrying about 20 feet of water. After a winding course of two 

 or three miles, from several points of which it could with very little dif- 

 ficulty be turned eastward into the main Snake, it flows with a still 

 rapid current into the more northern of two small lakes, known to us 

 as Beulah Lakes, which lie upon the lowest part of the divide and are 

 each from 600 to 800 feet across. The southern one has now no surface- 

 outlet, but marshy grounds extend to the more northern one, over which 

 17 G S 



