178 GEOLOGieAL SURVEY OF THE TEEEITOEIES. 



of the valley. Here the basaltic layer extends across the gorge, forming 

 an abrupt perpendicular wall, broken only on the side opposite that on 

 which we were. Here the water rushes down in a beautiful fall, its 

 beauty half-hidden by the dense foliage of the pines which surround it. 

 Ascending upon the basaltic platform, and looking back, the scene was 

 grand. High mountains in all directions, their rounded forms relieved 

 by numerous sharp peaks, formed the background, while in the fore- 

 ground beneath us lay the valley through which' we had come. The 

 central feature of the whole scene was the hot-spring formation, its pure 

 white color contrasting strongly with the green of the surrounding 

 vegetation. Turning again, the scene in front was different. Although 

 there was less of grandeur there was more of beauty. Before us lay low, 

 rolling hills clad in bright verdure and dotted with scattered groups of 

 pines. About a mile farther on wejDassed a second cascade. The water 

 flows down a bed of basalt, which is inclined at an angle of about 45°, 

 arranged in a series of ledges reaching from the top to the bottom, a 

 distance of about 200 feet. These ledges cause the water to be broken 

 into foam, giving it at a distance, the appearance of a mass of snow. 

 Bordering the cascade are chimney-like masses of red igneous rock. 

 The horizontal and vertical fissures in it make the resemblaiice to ma- 

 sonry very striking, l^ear here we obtained some good specimens of 

 silicified wood. 



The following day we reached the Yellowstone Eiver at the junction 

 of its two forks. Here we encountered gneissic rocks, and scattered 

 over the valley wei"e numerous granitic bowlders, their rounded form 

 plainly indicating that they must have been carried some distance be- 

 fore being deposited in their present position. Above the junction of 

 ;the two forks the main branch of the river emerges from a caiion, which 

 is over 500 feet in depth, its walls being almost perpendicular. The 

 walls have a capping of basalt, the columnar form of which is very dis- 

 tinct, especially at Column Rock, near the mouth of Tower Creek. 

 Tower Creek is a swift mountain torrent, which, after rushing through 

 a narrow gorge, with steep and often precipitous sides, suddenly dashes 

 over a ledge of rock, and falls perpendicularly a distance of 156 feet 

 into a rounded basin which the water has cut out of the solid limestone. 

 The width of the fall is about 20 feet. Eeaching the bottom the water 

 ihurries on through a short cai5on to the Yellowstone Eiver. Upon the 

 limestones rest volcanic rocks, trachytic in nature. These have been 

 so eroded by the action of the torrent as to leave tower-like masses 100 

 feet in height, standing isolated on the edge of the creek. Two of these 

 -columns stand, one on either side of the fall, at its edge. They are yel- 

 lowish in color from the presence of sulphur, and the exposure to the 

 weather has rendered them A^ery friable. The bank of the Yellowstone, 

 immediately opposite the mouth of Tower Creek, is about 600 feet high 

 and has two rows of basaltic columns, each one of which is about 25 feet 

 in height and 5 feet in diameter. Between these two layers, which are 

 200 feet apart, are beds which seem to have a large amount of sulphur 

 in their composition from their bright-yellow color. We were not able, 

 however, to cross the river to determine it. There are also, doubtless, 

 numbers of hot springs scattered along the edge of the river on that 

 side. A few yards above the mouth of Tower Creek, on a small stream 

 emptying into the Yellowstone Eiver, there was a hot spring and a 

 number of vent-holes giving off sulphureted and carbureted hydrogen. 

 The main spring is only 2 feet in diameter and about 18 inches deep. 

 It is close to the edge of the creek and gives oft' sulphureted and carbu- 

 reted hydrogen. The basin of the spring is a black, clayey material. 



