1922] EDWARDS, GEOLOGICAL WORK AT GRAND CANYON 95 



From the south side no streams enter the Colorado river for many 

 miles westward from the mouth of the Little Colorado, but on the 

 north side the greater rainfall, caused by the higher altitude of the 

 plateau on that rim, gives rise to a number of prominent streams which 

 have carved valleys of their own in the walls of the canyon. One of 

 the best known of these is immediately across the canyon from the 

 Hotel El Tovar, and is called Bright Angel Creek. It was so named by 

 the party of Major Powell, who, in 1872, descended through the canyon 

 of the Colorado, and, after being many days without clear water for 

 drinking purposes, discovered this bright and sparkling stream. It has 

 cut a long and narrow canyon directly at right angles to the course of 

 the main stream, and each little tributary has eroded a similar canyon 

 of its own. There are several others of these streams which enter the 

 canyon from the north side, but none of them are permanent waterways. 

 They exist only after a shower and in the rainy season of the year, 

 which is during July and August. The remainder of the time their 

 water is confined to the vicinity of springs and to pools in the deeper 

 parts of their beds. 



One of the principal roadways in this National Park, leads west- 

 ward about eight miles from the Hotel El Tovar to the head of the 

 Hermit Trail. This road follows closely the rim of the canyon and 

 leads directly to the various points which project far out from the 

 south edge of the canyon wall resembling peninsulas along the shore of 

 the ocean. From them one can obtain many fine views up and down 

 the canyon, and can see the river far down in the depths of the excava- 

 tion. From above, this appears like a brownish yellow ribbon or strip 

 of sand winding along at the very bottom of the Granite Gorge, and 

 one can scarcely realize that it is a stream about three hundred feet in 

 width and thirty feet deep at ordinary water level, and flowing at a 

 velocity of at least two miles per hour. At the rim no sound of rapids 

 can be heard and no break in the even current of the water can be de- 

 tected. When in flood, which usually occurs from May to July, the 

 depth of the river may reach one hundred feet and its velocity and 

 volume are then greatly increased. In the forty-two miles of the river's 

 course which leads through the heart of the Grand Canyon, it falls 

 about five hundred feet, or an average of twelve feet to the mile. The 

 water appears to be brownish yellow because of the great quantity of 

 sand and clay which is carried in suspension, and which was derived 

 from the erosion of its banks farther up in its course. It also moves 

 downward a considerable amount of rock which is rolled along by the 



