19 



object, and the profound silence which prevailed, produced a feeling that was 

 positively oppressive. When I then thought of the buttes beneath my feet, 

 with their entombed remains of multitudes of animals forever extinct, and 

 reflected upon the time when the country teemed with life, I truly felt that 

 I was standing on the wreck of a former world. 



The buttes are often specially designated from some supposed resemblance, 

 or other character, as Church Butte, Pilot Butte, Grizzly Butte,* &c. 



As before intimated, the more superficial table-lands of the Bridger basin, 

 as they appear in the vicinity of Fort Bridger, are composed of nearly hori- 

 zontal strata of various colored indurated clays and sandstones. In most 

 localities visited by the writer the clays predominate, and are usually greenish, 

 grayish ash-colored, and brownish. When unexposed they are compact, 

 homogeneous, and of stony hardness. In composition they vary from nearly 

 pure clay to such as are highly arenaceous, and gradate into those in which 

 sand largely predominates, and they usually contain few or no pebbles. They 

 appear to be more or less fissured, and break with an irregular and some- 

 what conchoidal fracture. Exposed to atmospheric agencies, moisture, and 

 frosts, they readily disintegrate, and the declivities of the buttes, generally 

 entirely destitute of vegetation, are usually invested with crumbling material 

 from a few inches to a foot or more in depth. When this loose material is 

 wet it forms tenacious mud, and along the course of streams in the ravines, 

 the deepest and most treacherous mire. Baked by the sun upon the plains, 

 it fixes the drift-pebbles and other stones as firmly almost as if imbedded in 

 mortar. 



In some localities the clays of the buttes abound in fresh-water shells, as 

 Unio, Melania, Planorbis, &c. Less frequently in other places they con- 

 tain land-shells, as Helix, &c. 



The sandstones are more frequently of various shades of green, but are 

 also yellowish and pass into shades of brown. They are compact and hard 

 when unexposed to the weather, and are usually fine-grained, but also occur 



*This name is applied to an extensive chain of buttes about ten miles to the south- 

 east of Port Bridger. Judge Carter informed me that the name originated from the 

 circumstance that an old trapper, Jack Eobinson, once reported that he had found a 

 petrified grizzly bear on the Butte. From the description of the petrifaction 1 have 

 no doubt it was that of the animal I have named iu the succeeding pages, Palseosyops, 

 the skull of which resembles that of a bear. 



