PEAi^.] DESCRIPTIVE GEOLOGY SNAKE EIVER AREA. 551 



Tlie thickness of the beds in the first of the two sections just given is 

 about 4,000 feet, taking the average angle of dip at 50°. In the second 

 section we have about 1,000 feet. 



The heights of the peaks in the Salt Eiver Eange are from 9,325 feet 

 to 10,988 feet. The greater portion of its drainage is towards Salt Eiver, 

 very few of the streams on the east side cutting into the head of the 

 mountains, as the western streams do. 



SALT RIVER. 



This is one of the important southern branches of Snake Eiver. It en- 

 ters the latter a few miles north of our district. Its extreme sources are 

 opposite those of the Western fork of Smith's Fork of the Bear, south of 

 Mount Wagner. 



Its valley is divided into two portions by a broad plateau-like mass of 

 hills that branch from the Salt Eiver Mountains. Through these hills 

 the river flows in a low caiion. 



The entire length of the valley in our district is about 38 or 40 miles 

 and the average width about 5 miles. The soil is coarse and graveUy, 

 especially in the lower valley. It is covered with abundant grass of excel- 

 lent quality. The upper valley is about 22 miles in length and about 3 

 miles in width. The course of Salt Eiver before it enters this valley is 

 west of south. Eising east of Mount Wagner it flows parallel to the 

 waters of Smith's Fork for about 7 miles, when it turns abruptly, making 

 an angle of 40°, and flows west of north. At the mouth of Wagner 

 Creek it turns more to the north and keeps a nearly uniform course to 

 the mouth of Smoking Creek, which comes in from the west, just above 

 the canon already referred to. This upper valley appears to be located by 

 an anticlinal from which the beds have been mostly removed. We find 

 indications of this anticlinal at the head of the canon on its east side,. 

 and along the east side of the valley the same gray sandstones and 

 hmestones are seen dipping in towards the mountains, as noted in the 

 section given on page 550. 



What these beds are I was unable to determine, and in Mr. St. John's 

 district they occurred with a great thickness, and he was unable to posi- 

 tively identify them. They resemble the beds noted to the southward 

 on Smith's Fork, and the strikes j)rolonged evidently fall on the same 

 strata. In the latter region I obtained Laramie fossils from the central 

 beds, and I think the whole series below the Laramie to the Jurassic is 

 present on the east side in that locality. These beds will be discussed 

 again under the head of Smith's Fork. 



The Lander cut-off road comes down the Upper Salt Eiver Valley and 

 crosses to Smoking Creek before it reaches the canon. This portion of 

 the road is used very Httle. The canon on Salt Eiver is six or seven 

 miles long and about 1,000 feet deep. Shoshone Creek joins Salt Eiver 

 about the middle of the canon. The lower valley of Salt Eiver con- 

 tinues northward from the canon until it is merged in the valley of 

 Snake Eiver, which has the same direction. The valley in this lower 

 portion is terraced. Between Glacier and Strawberry Creeks the soil 

 is gravelly, and the surface strewn with limestone pebbles and bowlders. 

 Although this portion of the valley is unfitted for agricultural purposes 

 it is covered with good grass. The valley is about six miles wide at the 

 widest part, and the elevation is about 6,000 feet. The river is crowded 

 to the west side, close to the rolling hills that separate Salt Eiver from 

 the branches of the Blackfoot. In this lower valley, on the east side, a 

 conglomerate shows at the edge of the mountains at several points. 



