470 KEPORT UNITED STATES GEOLOGICAL SUKVEY. 



LEWIS OE LAKE FORK. 



This stream rises in Shoshone Lake, opposite* the heads of the Fire- 

 hole and Bechler's Fork. Leaving Shoshone Lake, it flows into and 

 through Lewis Lake, then, x)ursuing a straight course a little west of 

 south, it reaches and joins the main river, at the south line of the Park. 



Shoshone Lake is purse-shaped, but, unlike most purses, its point of 

 discharge is at the bottom of the larger lobe. Its greatest length is 

 6J miles, its greatest width 4J, while the stricture is but ^ mile across, 

 and its area is 12 square miles. It receives three small affluents. Moose 

 Creek near its foot, Shoshone Creek at its head, and an unnamed stream 

 at the northern end of the lower lobe. Besides these there are a num- 

 ber of small branches, but collectively they contribute very little to the 

 lake. At the head of the smaller and upper lobe of the lake, *. e., at its 

 western end, is a collection of hot springs and geysers, discovered by 

 one of the parties of this survey in 1872, and known as the Shoshone 

 Geyser Basin. 



The shore of the lake is almost everywhere bold and densely covered 

 with timber. The stream connecting Shoshone and Lewis Lakes is but 

 3 miles in length, and is broad and sluggish. Lewis Lake is nearly pear- 

 shaped, the outlet being at the stem end. It is 3 miles long by 2 in width, 

 with an area of 4 square miles, with bold, heavily timbered shores. Be- 

 sides the main stream, the lake receives very little water from the gulches 

 opening into it. 



On leaving Lewis Lake, the stream first passes the western end of the 

 Eed Mountains, then enters an inclined table-land floored with basalt, 

 in which the stream has cut a naiTow, deep rift, scarcely discernible at 

 any distance, which extends nearly or quite down to the Forks. As I did 

 not follow the stream in this portion of its course, I quote the following 

 description of it from Professor Bradley's report :* 



In descending from Lake Lewis, the party fonnd the river banks lo-w and rocky 

 for a short distance before the stream enters a canon with walls 150 to 200 feet high, 

 in which were encountered sharp rapids and a vertical fall of about 30 feet. Then, 

 for a mile or two, the slopes are gradual, with narrow, swampy bottoms along the 

 river. About three miles below the lake, high, rocky banks indicate the approach to 

 a deep canon, which really commences at about 3|- miles, with perpendicular walls on 

 both sides, inclosing a narrow channel with a rapidly-sloping rocky floor, in some 

 places partially obstructed by huge tumbling masses of rock, but apparently without 

 any accumulation of gravel. Considerable rapids occur through nearly the whole 

 eafion, and one fall of nearly 50 feet was noticed. The canon deepens rapidly to from 

 700 to 800 feet, with widths of less than half the depths at the deepest precipitous por- 

 tions, though in some places widening above, so as to have sloping banks at an angle 

 of about 59° from the horizon. About 3 miles down it reaches its culmination and is 

 truly grand. It has none of the brilliancy of coloring so characteristic of the Yellow- 

 stone canon, but the somber tin tsofits gray, brown, and dark red, lichen-covered rocks, 

 variegated with smaller patches of green and yellow, constitute a peculiar style of 

 beauty, and add greatly to the eifect 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 porphyries and trachytes, with some porphyritic obsidian. Some two miles 

 below the end of the main canon, the cliffs close in again to the river, for a few hun- 

 dred feet, for a width of about 200 feet, with a height of 400 feet or more, forming a 

 suitable gateway to the caiion from below. 



THE KED MOUNTAINS. 



This is a small group of mountains, standing between Barlow's and 

 Lewis' Forks, and rising to a height a little exceeding 10,000 feet. The 

 name is derived from the prevailing color of the volcanic rocks which 

 compose them. The slight indication of a trend which they exhibit is 



* Eeport U. S. Geol. Survey. 1872 ; pp. 256, 257. 



