Cope.] -l4-U [Dec. 16, 



mltted to Prof. Co{):3, at whose inslauce the party was organized and 

 equipped. 



Dr. Hayden has made the observation that upon the eastern slope of the 

 Wind River mountains all the corresponding strata are visible from the 

 Silurian to the Cretaceous; this is also true of the northern slope of the 

 Owl Creek mountains, while the southern side does not exhibit such con- 

 tinuity of structure. Upon entering the basin from the south, the older 

 formations are seen to extend towards its centre for a distance of ten miles, 

 inclining at an angle of 30° to the north, while the level of the Tertiary 

 has been little or not at all disturbed since its deposition. That this 

 basin contained a separate and isolated body of water, limited by its pres- 

 ent boundaries, which were outlined about the beginning of the Wasatch 

 epoch, there is every reason to believe. A section made by the Big-Horn 

 at the southern extremitj^ shows the Tertiary to rest unconformably upon 

 a thick mass of buff colored sandstone, rather coarse in texture, somewhat 

 laminated, and towards the bottom interspersed with thin laj'^ers of im- 

 pure lignite varying from six inches to one foot in thickness. This sand- 

 stone most probably belongs to the Laramie series, but in the absence of 

 fossils the determination is by no means satisfactory. 



The Eocene sediment covers a large part of the basin, and cannot be 

 less than 4000 feet in vertical depth. This mass, once continuous over a 

 large area, has since been carved and weathered into many fantastic and 

 remarkable forms, presenting at once a bold and striking appearance, a 

 characteristic feature of the western Tertiary bad lands. 



Beginning at the southern limit at a point opposite the mouth of Meyers 

 creek, on the east side of the river, a series of low bad land bluffs, facing 

 to the west and gradually becoming higher as they proceed, describe a 

 gentle curve to the north, terminating at the river's edge 80 miles below. 

 The character of the country betAveen the river and these bluffs is a barren 

 sage brush plain, while back of the bluffs a high mesa occupies the coun- 

 try for many miles. On the west side, numerous rivers, creeks, and their 

 tributaries, putting down from' the Sieri-a Shoshone range, have excavated 

 tlie mass in every direction, leaving bold escarpments, high bad land buttes, 

 elevated tables, with innumerable gulches and ravines. Country of this 

 character stretches far away to the northern limit, near the Big Horn gap. 

 presenting that desolate and sombre appearance, so often met with in bad 

 land regions. 



Its composition may be described as consisting of various colored clays 

 alternating with layers of brown and blue sandstone, although that even- 

 ness of stratification by which a single layer of either, in one part, could 

 be identified in another, does not exist. Those exposures, for example, on 

 the east side of the Big-Horn are highly arenaceous, the clay and sand 

 existing in almost equal proportions, while in the exposures along the 

 Grey Bull river, and in the vicinity of Coryphodon butte, the quantity of 

 sand is greatly diminished, and is found in separate layers. The prepon- 

 derance of the red clay is a marked feature, and has called forth the 



