226 GEOLOGICAL SUEVEY OF THE TERRITORIES. 



8 feet in depth, which is practically the head of Henry's Fork, though 

 several small streams flow into it from various directions. Though the 

 shore is very winding, and numerous points project into the lake, yet, 

 as a whole, it is a pretty regular body of water, about three miles long 

 by from one and a half to two miles wide. Several small islands are 

 scattered over its surface. From its borders, which are mostly marshy, 

 the plain rises very gradually to the gravelly terrace of an old lake- 

 shore, from 80 to 90 feet above the present water-level. When at that 

 level, the lake would have been some eight or ten miles in diameter. No 

 higher terraces were apparent. The upper level is covered with sage- 

 brush, but the lower flat supports luxuriant growths of grasses, sedges, 

 and other rich forage-plants. Near Sawtelle's ranch, at the head of the 

 lake, large amounts of hay were curing in the hot sun ; while a mowing- 

 machine was still in active operation on the meadows. Messrs. Sawtelle 

 and Wurtz here conduct a large trade in fresh fish, caught in the lake and 

 its outlet, which they pack in ice and haul fifty miles to Virginia City, 

 They at first attempted raising stock on these rich meadows ; but the 

 immense numbers of horse-flies and gnats which breed in the swampy 

 borders of the lake soon compelled them to abandon that business. 

 They report that game is still abundant in the neighborhood — ante- 

 lope, deer, elk, moose, bear, and mountain-sheep, as well as smaller 

 animals. 



In approaching this basin, the trail passed with the river to the west 

 side of the valley, leaving the main mountain two or three miles to the 

 right. This consists of coarse volcanic sandstone, mostly composed of 

 obsidian. Two or three deep canons here reach the valley, showing 

 that water once worked powerfully in them, but these are now dry, 

 except where springs burst out of the sandstone at their very mouths, 

 and apparently have carried no water for many years past, except dur- 

 ing the times of most rapid melting of the snow in the spring. In 

 examinations made later by Mr. Bechler, when crossing westward from 

 the Fire Hole Basin, the uj^per course of these canons proved to be of 

 the same character; here and there large springs burst out, but soon 

 disappear again in the porous sandstones, which, in that direction, form 

 the surface of the entire mountain. Passing a little to the northward, 

 older rocks appear on the higher slopes of the mountain and soon form 

 its entire face, the volcanic rocks disappearing beneath the valley. 



On the opposite side, these appear again in the high mountain lying 

 directly south of Henry's Lake, known to us as Sawtelle's Peak, whose 

 lower spurs run down nearly to the lake-shore. The rugged precipitous 

 sides of the peak, without well-marked stratification, led to the suspicion 

 that it might be of volcanic origin, and it was accordingly visited by Mr. 

 Taggart and myself. It was found to constitute the eastern and north- 

 eastern wall of a great crater, some 1,200 or 1,500 feet deep, whose east 

 and west diameter is about a mile and a half, with a transverse diameter 

 of about a half mile. The sides are much washed down and the bottom 

 filled up; but, from the position of the portions of what was apparently 

 the original wall which are still standing, it is probable that the origi- 

 nal crater had very nearly the dimensions above given. The walls con- 

 sist of ragged, cellular, largely amygdaloidal porhpyry, containing crys- 

 tals of quartz, calcite, &c., partly weathering with a very rough surface, 

 partly decomposing into a coarse brittle sand, and making very treach- 

 erous footing. Lower down, the slopes consist of very dense, nearly 

 black, basalt. The western and northwestern walls were not visited; 

 but their style of weathering indicates much softer material than was 

 found on the part visited. Considerable portions of the crater, as well 



