XXII REPORT UNITED STATES GEOLOGICAL SURVEY. 



The Yampah or Bear Eiver deviates from a westerly course only for a 

 few miles occasionally. Like White Eiver, it Hows through a plateau 

 country, which rises gently from the river back for a distance of about 

 eight miles. South of the river lie the Williams Eiver Mountains, which 

 have a gradual slope to the north. Williams Fork, flowing from a south- 

 eastern direction, joins the Yampah Eiver west of the junction. The 

 Yampah traverses the country more or less in a caiion, occasionally emerg- 

 ing into an open, grassy valley, then enters a deep caiion, cuts through 

 the Y'ampah Mountains, when it joins with the Snake Eiver. The place 

 of junction resembles a fine park, surrounded on all sides with eroded 

 terraces and plateau spurs that rise by steps to the divide on either side. 

 This park is about eight miles in length from east to west. After leav- 

 ing this park the river enters a huge fissure in the mountains, where it 

 remains until, completing its zigzag course, it joins the Green Eiver in 

 longitude 109° 40' and latitude 32°. After the junction with the Yam- 

 l)ah, the Green Eiver continues in a canon for fourteen miles, where it 

 passes through the picturesque palisades of Split Mountain into an open, 

 broad valley, longitude 109° 15', latitude 40° 28', from which point it 

 takes a southwest direction through the Wamsitta Valley, where it 

 unites with the White Eiver. Into both White and Yampah Elvers nu- 

 merous branches extend from either side, forming deep caSons the 

 greater portion of their length. We may say, in brief, that the sides 

 of the valleys expand and contract, at one time forming the beautiful 

 grassy valleys which in olden times were celebrated as the favorite win- 

 tering places for the trappers, or contracting so as to form narrow 

 caiions or gorges with walls of varied height. 



The walls of Yampah OaQon average 1,000 feet, while the mountains, 

 receding back to the northward, attain an elevation of 4,200 feet, while 

 the highest point of the plateau on the south side is 3,400 feet above the 

 river-level. 



Of the plateaus between White and Yampah Elvers, Yampah pla- 

 teau is the largest, and occupies an area of 400 square miles. The sur- 

 face of the summit is undulating, and on the south side it presents a 

 steep face, several hundred feet in height, covered with debris, render- 

 ing it almost inaccessible. This plateau is covered with excellent grass, 

 and gives origin to numerous springs, all of which dry up within a short 

 distance of their source. 



As a whole, this district is very arid, barren, and almost destitute of 

 tree vegetation. 



The total number of stations made hy Mr. Bechler in the district as- 

 signed to him was 40, and the entire area was about 3,000 square miles. 

 Barometric observations were made whenever needed, and about 2,000 

 angles of elevation and depression, with fore and back sights, so that 

 material for obtaining correct altitudes is abundant. 



The rocks of this district embrace all the sedimentary formations yet 

 recognized by the investigators who have studied the region that lies 



