GEOLOGICAL SURVEY OF THE TEREITOEIES. 261 



Along the shor&s of Jackson's Lake there are no outcrops whicli 

 would enable one to decide where the different strata lie ; but, at its 

 southern end, there are high knobs of porphyries and trachytes, which 

 indicate, by their position, at least a former connection with the more 

 northern beds, which we traced to within five miles of the northern end 

 of the lake. 



Jackson's Lake is a very irregular body of water, much cut up along 

 its borders by long, narrow promontories jutting out into it from both 

 sides, and containing one large island, -which nearly separates the lake 

 into two. The main lake is from two and a half to three miles wide, 

 and the total length is about eight miles. In the soundings taken by 

 Mr. Adams, the greatest depth found, 258 feet, was about a mile from 

 the western shore. The series of soundings was far from complete, by 

 reason of a squall coming down Crom the Tetons and raising dangerous 

 waves, so that they had to give up the rest of the work. The lower 

 slopes of the more northern Tetons come sharply down to the lake on 

 the west, and these steep slopes, together with the tangled undergrowth 

 of willow, Cottonwood, mountain-ash, and iron-weed, with occasional 

 box-elder and maple and some tracts of fallen timber, make passage 

 along there difficult for a train ; but its other shores are surrounded by 

 low hills and by broad meadows, largely occupied by beaver-dam and 

 other swamps. These fiats are much cut up by bayous, and include 

 several ponds of considerable size. Others are found among the rounded 

 hills of gravel, which remain from the upper terrace of the old river- 

 border. Two of these, lying from two to three miles east of the outlet, 

 toward the valley of Buffalo Fork, are each about two miles long by a 

 half mile wide. They apparently occupy portions of ancient river-chan- 

 nels. A stream of about the size of Barlow's Eiver, with broad gravel- 

 bottom and rapid current, comes out of the hills opposite the lower end 

 of the lake and joins the Snake just after it has escaped from the lake. 



The views from the east shore of the lake are v/onderfullj^ grand. 

 The Tetons rise majestically from its western shore to the height of 

 7,000 feet above its surface, with sharp slopes and walls of bare rock 

 above, and their bases buried in a dark mass of pine and spruce, while 

 at this season (September 24) their snow-covered summits give the be- 

 holder a strong sense of sublimity. At times they are wrapped in 

 heavy masses of cloud; but even then they are grand. The accompany- 

 ing sketch of the face of the range, as seen from near the North Gros 

 Ventre Butte, has been copied from Mr. Bechler's field-notes. (Fig. 50.) 



A few miles below the lake, Buffalo Fork enters from the east through 

 a broad valley with grassy and willowy bottoms, bringing a very large 

 body of water. These bottoms contain some large groves of Menzies's 

 spruce, {Ahies Menziesii,) whose peculiar cones were seldom seen else- 

 where by us. iNiear the mouth of the stream gray and buff, fine-grained, 

 shaly sandstones of indeterminate age dip sharply to the southeast, 

 and similar rocks appear in the bed of Snake River, at the ford just 

 above the mouth of Buffalo, but the dips are hero much confused. 

 Mr. Bechler followed the Buffalo nearly to its head, and reports that, 

 for about twelve miles from its mouth, its broad, open valley shows no 

 rock, but has rounded slopes covered with "quaking asp,^^ {Populus 

 tremuloifles,) and bottoms full of beaver-dams. About twelve miles up, 

 the valley narrows to a caiion from 350 to 400 feet deep by from 50 to 

 200 feet wide, ftr about three miles, with coarse, gray sandstone walls. 

 About one and a half miles of a i-ounded basin, with beaver-dams, 

 then intervenes before reaching the second caiion, which has nearly the 

 same character as the first and is about two miles long. A broad basin 



