20 GEOLOGICAL SURVEY OF THE TERRITORIES. 



posing view of Laramie Peak, with the intervening mountain ridges. 

 They show a trend about southeast and northwest. Between Horseshoe 

 and La Bonte the black gneiss beds must be two thousand to three 

 thousand feet in thickness, extending in long lines across the country 

 nearly north and south, just projecting above the surface, nearly vertical. 

 For ten miles or more the White Biver tertiary beds conceal the moun- 

 tain flanks ; but from five to fifteen miles northeast of the range, toward 

 the Platte Biver, the older beds are uncovered over very restricted areas. 

 At the head of a little branch of La Bonte two ridges of reddish sand- 

 stone and limestone rise up from beneath the tertiary beds, inclining 10° 

 to 15° east of north. The little dry branch has cut through the rift 

 between the ridges caused by the uplift, showing one of them to be coin- 

 posed mostly of bright brick -red sandstone, with a layer of light gray 

 sandstone tinged with red, (triassic;) while the other ridge is made up 

 of carboniferous limestones and sandstones. In the limestones are 

 seams of chalcedony, from which most of the varieties of flint scattered 

 through the drift are doubtless derived. Sometimes these isolated hills 

 are elevated in such a way that the two sides incline in opposite direc- 

 tions, forming a fissure at the summit, through which the waters find 

 their way, thus wearing out a gorge or canon. In the interval between 

 Horseshoe and La Bonte Creeks, and west of the Platte Biver, the older 

 sedimentary rocks, as carboniferous, triassic, Jurassic, and cretaceous, 

 are uncovered in spots by denudation, always inclining from the moun- 

 tains at a high angle. The pine forests in the mountains at the sources 

 of the Horseshoe and the La Bonte are more dense, and the timber 

 larger, than in any other portion of the range that we have seen. Great 

 abundance of ties for railroad purposes could be procured. Our camp 

 in the valley of the La Bonte was a pleasant one ; a fine, luxuriant 

 growth of grass covered the immediate bottoms of the creek, and our 

 animals found excellent grazing on the uplands also. The creek is bor- 

 dered with bitter and sweet cottonwood, box elder, and large tree wil- 

 lows to a considerable extent. The soil is certainly fertile enough, and 

 where it can be irrigated, will produce fine crops of all kinds. This 

 will prove one of the best valleys along the North Platte, both for agri- 

 cultural and pastoral purposes. 



On the morning of the 16th we left La Bonte Creek for Fort Fetter- 

 man, which is located near the junction of La Prele with the North 

 Platte. The atmosphere was very smoky, limiting our range of vision 

 considerably, so that we could not see the mountains distinctly. Just 

 north of the La Bonte are a series of anticlinals and synclinals, which 

 are somewhat different from any before observed. The road passes 

 along a synclinal valley, with the red sandstones (triassic) inclining 

 southwest on our left, and the Jurassic, with an outcropping of the 

 red beds at the base, about a mile distant, on our right, dipping north- 

 east. The beds on our left dip about 30°, while those on the right not 

 more than 10° or 15°. 



The end of one ridge inclining southwest apparently juts up against 

 another inclining northeast. These irregularities are local, and are due, 

 perhaps, to the variableness of the internal forces that produced the ele- 

 vations and the different degrees of strength of the earth's crust. 



There is an immense ridge, or "hog-back," extending from the La 

 Bonte to the Bed Buttes, which forms an illustration of these apparent 

 irregularities in the exhibition of the interior forces, on a large scale. We 

 can express them no better than to call them " puffs," or local risings of 

 the earth's surface, which cause a fracture along the central axis in 

 rather reguiar lines, and this fracture gives access to atmospheric influ- 



