454 REPORT UNITED STATES GEOLOGICAL SURVEY. 



which gives to the ledges a beautiful orange-reddish tint seen at a dis- 

 tance. 



Looking up the Gros Ventre Valley, the limestones are soon succeeded 

 by a heavy series of red arenaceous deposits, "which continue several miles 

 along the north side of the stream, and which, in part at least, are the 

 same mentioned by Dr. Hayden. This point was also visited by Profes- 

 sor Bradley, who reports the following section a short distance within 

 the valley, on the north side : 



Section in the debouchure of the Gros Ventre Valley. 



tl 1. White, friable, false-bedded sandstones, 10 feet. 



" 2. Covered space, about 100 feet. 



" 3. Irregularly-bedded, pale-gray and buff, partly bituminous, mag- 

 nesian limestones, 50 to 60 feet. 



" 4. Pale-red friable sandstones, darker and shaly below, 300 to 350 

 feet. 



" 5. Compact, fine-grained, gray sandstone, 15 to 20 feet. 



" 0. Brown, coarse, friable, false-bedded sandstone, 60 to 80 feet. 



u 7. Coarse, friable, red sandstone, 40 to 50 feet. 



" 8. Compact, dark-drab, fossiliferous limestone, 300 to 400 feet." 



The bed No. 1, Professor Bradley refers to the late Tertiary ; No. 3 is 

 provisionally referred to the Jurassic, although no fossils are observed 

 in this horizon ; No. 4, Triassic ; and No. 5-8, Carboniferous. 



The second and last visit to the higher portions of the range was made 

 in the ascent of the mountain chosen for the topographical Station, 

 XLVI. This occupies a commanding summit at the northwest end of 

 the range, about 10,500 feet above sea-level, from which the view over- 

 looking the lower portion of the Gros Ventre Valley, and a part of the 

 Little Gros Ventre Valley in the opposite direction, is particularly in- 

 teresting and instructive. Keeping the crest of the main foreland ridge, 

 the way lies over Carboniferous deposits the whole distance between the 

 foot of the spur just south of the debouchure of the Gros Ventre and 

 the summit, along a general southeast course of about six miles. The 

 first two miles is a rather steep ascent of about 2,500 feet, flagged with 

 light and dark-drab cherty limestone, with hard brittle siliceous layers. 

 The limestone contains numerous characteristic fossils, conspicuous 

 among which are the usual forms of Zaphrentis. Gaining the north- 

 west shoulder of the spur, the remainder of the way lies along the broad 

 crest of the ridge, with a gradual and quite uniform rise to the foot of 

 the culminating peak, the last 400 feet in the ascent being abrupt. 



The southern or southwestern slope of the ridge is deeply furrowed by 

 numerous short ravines tributary to the Little Gros Ventre, that render 

 this aspect exceedingly broken ; but on the northeast the slope is more 

 gradual, although it is also much cut up by drainage channels, fall- 

 ing with the dip of the strata, which is a little east of north, though 

 the direction is variable, at angles of 15° to 30°. For a considerable 

 distance the crest of the ridge nearly corresponds to the strike of the 

 limestone strata, when it bears a little more to the south, and at the 

 same time rapidly rises into the bare Alpine heights, where the fir trees 

 are gathered in beautiful clumps, and the soil, based upon remnant 

 patches of red arenaceous deposits, decked with many bright blossoms. 



The summit of the mountain forms a short north-south ridge, rounded 

 on the west side to the escarpments of the buff-gray magnesian lime- 

 stones which skirt this side of the mountain, overlooking the gorge-like 



