GEOLOGICAL SURVEY OF THE TEREITOEIES. 267 



bnttes lie east of the more nortbern part of this one, and evidently 

 originally formed one with it. 



These buttes greatly narrow the plain, which, immediately below 

 them, expands into Jackson's Little Hole, whose flats are mainly ui)on 

 the east side of the river and measure about four miles wide by per- 

 haps ten miles long. Here, also, the sage has been burned off and re- 

 placed by grass. For several miles, from above the mouth of the Gros 

 Ventre, the river has gravelly bottoms from half a mile to three-fourths 

 of a mile wide, cut up by the several channels and partly occupied by 

 beaver-dams. Of course, fords are numerous. 



The only practicable pass across the Teton Range, so far as known, is 

 about opposite to these South Buttes; and our main party left the river 

 at this point. Mr. Taggart reports both slopes of the pass tolerably 

 regular and gentle, except for a short distance just at the summit, but 

 that the eastern is somewhat the steeper. The Carboniferous limestones, 

 which were the only rocks noticed until the summit was passed, are 

 nearly horizontal, have only a slight southerly or southeasterly dip ; but, 

 in descending the western slope, this dip increases to about 45° ; and 

 overlying, red, shaly sandstones, probably of Triassic age, appear at one 

 point on the trail, while limestones, apparently those previously referred 

 to -the Upper Silurian, form considerable cliff's or spurs, a short distance 

 to the northward. There would seem to be considerable displace- 

 ment thereabout. The porphyries of Pierre's Hole appear at the mouth, 

 of the pass, at the elevation of about 7,000 feet, and form all the foot-hills 

 of the mountains on the southwest side of that basin, until the actual 

 bottoms of the Snake are approached, where the basalt appears. The 

 track of the party lay so far out in the basin that there was little or no 

 opportunity for examining the character of anything more than the 

 foot-hills of the western mountains. 



At the lower end of Jackson's Little Hole, the so-called Grand Canon 

 of the Suake commences. The river turns sharply to the eastward a,nd 

 cuts through the laminated sandstones which apparently overlie the 

 Carboniferous limestones. Just at the mouth of the caiion, the upper 

 terraces close in, and are capped by bastioned walls, 100 feet or more in 

 height, of a pale-red sandstone, overlaid, as we see in looking backfroni 

 lower down the canon, after this turns south again, by heavy beds of 

 dark-red, shaly sandstone, appearing like, and occupying nearly the 

 relative position of, the Triassic (?) on the Gros Ventre, except that, 

 below them, there come in several hundred feet of thick and thin bedded 

 and shaly, gray and green sandstones, with interlaminated calcareous 

 shales. These contain plant-remains, but so thoroughly comminuted 

 that I was not able to find a single recognizable fragment. At the angle of 

 the canon, these dip strongly to about N. 78^ E., and a long section of 

 them is exposed on the east side of the stream ; but in about a half mile 

 they become horizontal, and, again, a mile lower, at the mouth of 

 Hoback's Eiver, dip 10° to about S. 63° W, 



Hoback's, so named for a hunter of the Pacific Fur Company in 1812, 

 by i\lr. Wilson G, Hunt, as reported in Irving's Astoria, brings in a 

 large volume of water from the eastward and jilainly drains a large 

 area upon the western slope of the Wind River Mountains. Its valley, 

 though narrow near its mouth, was at one time the favorite route for 

 the Indians in crossing to the Green Eiver Valley ; but, latterly, they 

 have preferred the Gros Ventre route for some reason. The red beds 

 hold a prominent place near the top of the high cliffs, for a half mile or 

 more above the forks, but the valley is too winding to give much of a 

 view. Just below here, a strong creek comes in from the west, appar- 



