bp.johk.] MT. LEIDY HIGHLANDS. 461 



the region to the north, to be noticed presently. The long undulating 

 slopes descending from the watershed south of Black Bock Creek reveal 

 light-huff arenaceous deposits wherever the surface is broken by the 

 bluffs and not concealed by forests, which latter thickly cover the more 

 elevated portions. In the bluffs along the narrow valley of the Black- 

 foot appear frequent exposures of light-drab clay and soft buff-gray sand- 

 stones, which weather in shelving surfaces, and in the promontory point 

 at the confluence of the Buffalo Fork buff sandstone ledges outcrop, 

 dipping gently northeastward. 



In the low aspen-covered upland intervening between the Elkhorn and 

 Buffalo Fork a fair section of these strata may be seen. This belt pre- 

 sents a succession of south-facing low bluffs, with long gentle slopes to 

 the northward, a conformation of surface determined by the character 

 and position of the subjacent rock strata, which uniformly dip in the 

 direction of the gentle declivities. In the lower extension of the bluffs 

 north of the Elkhorn, light-brown earth, with indurated layers, appears 

 in the steep slope, which is strewn with the water-worn pebbles and 

 bowlders that enter largely into the composition of the unconsolidated 

 superficial deposits in this region. Higher up the valley to the east the 

 bluffs are composed of rusty and light buff soft sandstone, bedded in 

 light-drab, clayey material, dipping northeastward at angles of from 10° 

 to 15°. In the next ridge, less than a mile north, occur rusty-buff, shaly, 

 and concretionary sandstones, interbedded with softer deposits which 

 weather into a fine light-brown soil. North of the last, a similar ridge 

 shows a ledge of light-buff sandstone associated with thin irregular lay- 

 ers of rusty ferruginous sandstone; and in a still higher bluff, the north- 

 ern slope of which descends to Buffalo Fork, a heavy bed of soft, light- 

 buff sandstone, with rusty and buff indurated layers, appears in the 

 upper third of the abrupt acclivity, forming an exposed thickness of 50 

 to 100 feet, associated with drab and brown earthy deposits, the disinte- 

 gration of which produces a light-drab loamy soil. The latter sandstone 

 resembles the ledge occurring in the base of the cone of Mount Leidy. 

 The light sandstones outcrop in the ravines intersecting the aspen ridges 

 400 to 500 feet above the Elkhorn. Patches of "alkali" soil were here 

 met with, which, together with the excellent pasturage, may account for 

 this locality being a favorite resort of elk and deer, the abundance of 

 whose antlers scattered over these uplands suggested the name of the 

 above-mentioned stream. The higher upland slopes also are strewn with 

 more or less drift material, consisting of thoroughly-rounded quartzite 

 and gneiss bowlders and occasional fragments of basalt. 



The exposures above alluded to are represented in an accompanying 

 diagram, in which an attempt is made to show their probable relations to 

 the deposits occurring in the mountain borders on the north and south. 



BUFFALO FORK AND SNAKE- RIVER DIVLDE. 



The lower course of the Buffalo Fork winds through a beautiful valley 

 for the distance of about eight miles, when it expands into the Snake 

 bottoms, east of the outlet of Jackson's Lake. The valley is occupied 

 by low terraces, and rather wide alluvial bottoms, with extensive tracts 

 of wet meadow-land, interspersed with thickets of willows. Along the 

 north side the hills are bolder than the south-side upland border, and 

 are well wooded with pines and spruces, and at many points in the some- 

 what broken declivity limited exposures of their component strata appear. 



Below the mouth of Black Bock Creek a hue of highish bluffs borders 

 the right bank of the river for a short distance, in which a thickness of 



