GEOLOGICAL SUEVEY OF THE TERRITOEIES. 241 



A small stream, carrying, perhaps, 15 feet of water, enters tlie river 

 from the west, just below the mouth of Iron Spring Creek, It rises far 

 up on the western divide. About a half mile up from the river, we enter 

 a sharp, narrow canon, along which small hot springs still occur, and 

 arrive, in about a half mile farther, at a tine fall and cascade, some 80 

 or 90 feet high. The chief interest of the spot is in the inclined bedding 

 of the volcanic sandstone, which dips strongly to the southwest. So far 

 as I could judge, this was not consequent upon disturbance and up- 

 heaval of the beds, but upon the slope of the surface upon which 

 the materials were originally deposited. Upon the west side of Sen- 

 tinel Branch, I found westerly dips, and upon the divide, toward 

 the Yellowstone, northeasterly di[)S. Though the question cannot pos- 

 itively be decided without loany more detailed observations, yet I am 

 strongly inclined to believe that we have at these points remnants of the 

 outward slopes of a huge crater, whose central area was large enough 

 to include most if not all of the heat- vents of the two geyser-basins. 

 Possibly there was a central cross-division between the two basins; but 

 I noticed no decisive dips thereabout. On the foot-hills of the east- 

 ern ridge, perhaps a hundred and fifty yards southeast of Giantess, 

 westerly dips occur, which, according to the above supposition, must 

 represent the internal slope of the crater. 



Mr. Stevenson returned from Virginia City with supplies on the last 

 day of August, and we started upon our return-trip the next day. Stop- 

 ping one day in the upper basin, to make our final observations upon the 

 geysers, whose like we expected to see no more for years, we again 

 moved southward on September 3. 



Above Old Faithful, which is recognized as the last large geyser of 

 the upper basin, there are only a few hot springs, mostly small, includ- 

 ing one small geyser. The valley soon narrows to a deep, impassable 

 caSion, with perpendicular walls of trachyte, with nearly vertical dips 

 and east and west strike. The trail is here forced to the top of the 

 bank, following the east side of the caiion, and, in the next half mile, 

 passes close by a set of beautiful cascades at the head of long rapids. 

 The principal fall is 30 feet high and 40 feet wide, with a side jet about 

 o feet wide, like a mill-tail. The water was about 1 foot deep on the 

 crest of the fall. Fifty yards below, all this water is forced through a 

 passage only about 5 feet wide, and rushes with great violence into a 

 deep, still pool below. From a rocky point directly in front of the fall, 

 there are fine views up and down the ravine; and it is well worthy of 

 a ^'isit from all who would see the beauties as well as the wonders of the 

 gey.^er-basins. The main fall much resembles the Middle Fall at Trenton, 

 Isew York. From this point, the parties of 1871 turned across the divide 

 toward Yellowstone Lake. The rapids above the fall are moderate, and 

 the banks spread out into a flat bottom, much of which is swampy. To 

 avoid this swampy ground, the trail, which here crosses the river, turns 

 up over the bounding range of hills on the west. In the hollows, we now 

 find many small ponds covered with lily-pods ; but only a few of the 

 yellow blossoms appeared. A few of these ponds have small outlets, and 

 small but apparently constant supplies of water, but most of them are 

 entirely inclosed by hills. The surface is here densely timbered, but 

 mostly with young growth. 



These hills soon approach the river again, which has here a very 

 narrow valley. This, however, suddenly widens again Into a third 

 geyser basin. The first intimation of hot springs, if we follow up the 

 river-bank, is a strong column of steam appearing among the timber 

 on the east side of the valley, just as we enter the basin. Mr. Taggart 

 16 G s 



