FORT BRIDGER. 75 



rocks and some sandstones, the former greatly predominating. In 

 some places, layers of blue and red clay, of considerable thickness, 

 were observed, and also gray argillaceous limestone ; but owing to 

 the surface of the rocks being covered by the clay detritus, no 

 complete sections of them were obtained, nor were any fossils found 

 in them. Farther on, upon Black's Fork, a ridge was crossed in 

 which the different layers of the rocks were quite apparent. Here 

 two strata of coarse reddish sandstone, which disintegrated but 

 slowly, were prominent. They were separated by layers of lime- 

 stone, shales, and clay. The shales were so nearly horizontal that 

 no dip could be ascertained. Following the valley of Black's Fork, 

 we passed, in the afternoon, strata of green and white sandstone, 

 whitish shales, and clay, but too much decomposed to afford us any 

 fossils. In the valley were found some blocks of limestone, wholly 

 made up of the debris of shells. The valley of Black's Fork, in the 

 vicinity of Bridger's Fort, is three or four miles broad, and many 

 of the numerous little branches into which the stream is divided 

 are handsomely fringed with thickets of cotton-wood. The soil is 

 composed of the detritus of the surrounding rocks, and huge blocks 

 of metamorphic rock, and some trap and serpentine, are found upon 

 the surface. At the fort we were shown a piece of rock, evidently 

 volcanic, in the cells of which were contained some particles of 

 gold. It was stated that it had been found in the bed of Black's 

 Fork in the vicinity. If so, it must have been washed down from 

 the Uintah chain of mountains, a lofty range to the south, in which 

 the stream heads. These mountains were at this time covered with 

 snow for a considerable distance from their summits ; but of their 

 lithological formation no opinion could be formed, as their great 

 distance precluded all opportunity of examining them. The strata 

 of the hills around the fort were nearly horizontal, and consisted 

 of gray limestone, clayey and slaty shales, and sandstones. Some 

 few miles up the stream, sections of these rocks were found, from 

 which some fossils were obtained. In the beds of the stream were 

 found rounded rocks, composed principally of metamorphic sand- 

 stone, and some marble. The same rocks were seen in horizontal 

 strata on the hills. 



From Fort Bridger there are now two routes as far as the Hum- 

 boldt or Mary's Biver, where they again unite. The old road 

 strikes Bear Biver, follows down its valley by the Soda Springs to 

 Fort Hall, whence it pursues a south-westerly course to the Hum- 

 boldt. By this route a northing of nearly two degrees is made, 



