56 REPORT OF THE SECRETARY. 



dry canons and gorges, with scarcely any grass or timber. From the 

 White Eiver agency, White Eiver takes an almost due west course for 

 about eighteen miles, most of the way through an open valley, with 

 here and there a few narrow gorges. About fifty miles below the agency 

 the valley opens into a broad barren expanse, with scanty vegetation. 

 Soon after the river enters a canon, the walls of which increase until it 

 flows into tfce Green. 



The Yampah deviates but seldom from a westerly course. Like 

 the White, it flows through a plateau country, which rises gently 

 from the river back for a distance of about eight miles. South of 

 the river are the Williams Eiver Mountains. The Yampah traverses 

 the country more or less in a canon, occasionally emerging into open 

 grassy valleys. Where the Snake, one of its tributaries, comes in there 

 is a park about 8 miles in length from east to west, surrounded on all 

 sides by eroded terraces and plateau spurs that rise by steps to the 

 divide on either side. Leaving this park, the river enters a huge fissure, 

 and continues in canon until it joins the Green, in longitude 109° 40' 

 and latitude 32° N. After the Yampah joins it, the Green also con- 

 tinues in canon for the greater part of its length. All these rivers have 

 numerous branches from both sides, forming deep canons the greater 

 part of their length. As a whole, the district is very arid and barren, 

 and almost destitute of trees. The total area surveyed by Mr. Bechler 

 is about 3,000 square miles. The rocks of the district, studied by Dr. 

 White, the eminent palaeontologist, embrace all the sedimentary forma- 

 tions yet recognized by the investigators who have studied the region 

 that lies between the Park Eange and the Great Salt Lake, viz, from 

 the Uinta quartzite (which underlies the Carboniferous) to the Brown's 

 Park group, or latest Tertiary, inclusive. Much information was also 

 obtained concerning the distribution of the local drift of the region, the 

 extent and geological age of outflows of trap, &c. The brackish-water 

 beds at the base of the Tertiary series, containing the characteristic fos- 

 sils, were discovered in the valley of the Yampah. They are thus shown 

 to be exactly equivalent with those from the valley of Bether Creek, in 

 Wyoming Territory. The work of the past season shows very clearly 

 the harmonious relations of the various groups of strata over vast areas; 

 that, although there may be a thickening or a thinning out of beds at 

 different points, they can all be correlated from the Missouri Eiver to 

 the Sierra Nevada Basin. Dr. White remarks that the line between the 

 Cretaceous and Tertiary epochs must be drawn somewhere, but that it 

 will be strictly arbitrary, as there is no well-marked physical break to 

 the summit of the Bridger group. 



The Zoological division was in charge of Dr. Elliott Coues, U. S. A. 

 The party leit Cheyenne on the 15th of August, and traveled westward 

 to Laramie Plains and thence southward into and through North Park. 

 From North Park they proceeded to Middle (Egan) Park, and finally 

 returned to Cheyenne via Berthoud's Pass and the plaius east of the 



