GEOLOGICAL SURVEY OP THE TERRITOHIES. 259 



A short distance southwest of Beulah Lakes, over a divide about 300 

 feet high, and at a level about 100 feet lower, Mr. Bechler found two other 

 small lakes, at the head of a branch of the stream which eaters Falls 

 Eiver from thosouth, just above the Great Falls. The upper one has an 

 area of something over one hundred acres, with rocky banks, and flows 

 to the lower, which occupies about 40 acres in the center of a marshy 

 basin of perhaps a hundred and forty acres. 



Southeast of these latter lakes, over a divide about 350 feet high, 

 we reach the head of a valley running eastward to the main Snake. Its 

 upper portion is a flat basin, about one and a half miles long by a mile 

 wide, bounded ou the east and north by from 400 to 500 feet of volcanic 

 rocks, of which the upper 200 feet present a vertical front, while the 

 remainder is mainly covered by a slope of tumbling rubbish down to 

 the stream. The other slopes are rounded, as are also most of those 

 along the lower course of the stream down to its junction with the Snake. 

 All this wide area, from these northern slopes of tlie Teton Eange 

 nearly to the Ty ghee Pass and to the mountains on the north side "of 

 the Upper Madison, though actually quite elevated, is relatively much 

 depressed below the summits of the limestone, quartzite, and granite 

 mountains on either side. From the general distribution of the volcanic 

 rocks, as well as from facts observed elsewhere, I am inclined to believe 

 that, before tlie ejection of these immense bodies of lavas, there was 

 here a broad valley, through which the drainage of the upper mount- 

 ain-region to the eastward found its way out to the great basin of the 

 Snake, while the canon by which it now escapes through the high 

 mountain-mass south of the Tetons had not been cut down. 



Immediately opposite the camp at the mouth of Lake Fork, there is 

 a consider<ible cluster of dead and dying hot springs. Several mounds 

 indicate the former positions of geysers of considerable size. The temper- 

 atures often springs were taken by IMr. Taggart, varying from 102° to 

 158°. Three were above 150°. The deposits are now rapidly disintegrat- 

 ing. U])on one large conical mound this process had developed a col- 

 umnar or fibrous condition of the geyserile. Similar spring-deposits 

 also occur on the west side of the river, from one to four miles below 

 this camp, and some of the mire-holes so common in the Fire-Hole 

 basins were also encountered. Upon looking back from below, two 

 large columns of steam were seen, about a mile up the Beaver-Dam 

 Creek, which seemed to indicate the possibility of geysers still existing 

 there. The lower part of that stream was full of purple-nacred unios, 

 aj^parently like, or closely allied to, those found in the branches of 

 Henry's Fork. 



Along the east side of the river, the face of the high ridge shows the 

 following rocks, according to notes taken and specimens brought in by 

 Mr. Taggart : — At the base lie about 200 feet of white and light-graj- 

 quartzites, overlaid by from 500 to (500 feet of light-drab and dark-gray 

 limestones, and about 100 feet of gray sandstones, followed by heavy 

 beds of red, shaly sandstones, apparentl^^ the same as those seen higher 

 up the river. I am not satisfied as to the age of either the limestone or 

 the quartzite. The ridge is capped with beds of porj)hyritic trachytes, 

 having a dip of about 30° to the southeast, while the limestones beneath 

 di[) about 40^ in the same direction, showing that their tilting com- 

 menced before the deposition of the trachytes. 



The main trail crosses the Snake about a mile below camp, and 

 passes over the hills so as to cut off a considerable bend of the river. 

 From six to eight miles below the forks, a spur, which runs nearly to 

 the west bank of the river, shows a high bluff face of porphyiitic 



