210 GEOLOGICAL SURVEY OF THE TERKITORIES. 



Henry's Fork and the main Snake Elver, and were separated from the 

 basalt plain to the west by a broad depression of springy ground, which 

 is probably occupied by the river in times of Hood. This was probably 

 once a channel, if not the main one, of Henry's Fork. It is even possi- 

 ble that this, with the valley on the east side of the buttes, formed one 

 broad river-plain before the eruption of these hills ; for these Crater 

 Buttes, as we called them, are old volcanic vents. The more northern 

 "was examined with some care. It rises about i500 feet above the river, 

 upon an oval base of about one by one and a half nules in diameter. Its 

 crest is rugged, sho^ying some small clitfs, while its slopes consist 

 mostly of sliding sand, both tine and cwirse, and are njostly more or less 

 covered with a straggling growth of bushy shrubs and small i)ines and 

 cedars. Its crater is about a half mile long by about a (piarter 

 mile wide and perhaps 150 feet deep. At one or two points, small 

 quantities of pretty compact lava W'ere found in thin layers; but the 

 mass of the rock exposed, inside and out, is mainly a sandstone, thinly 

 laminated and A^ery friable, consisting of comminuted scoriaceous and 

 compact lavas, including many well-rounded ])ebbles of quartz and 

 l)artially-rounded masses of basalt and other forms of lava. These peb- 

 bles evidently came out of one of the beds of river-gravel Avhich are in- 

 terlaminated Avith the basalt layers, and assist in proving the comi^ara- 

 tively recent date of the construction of these cones. The stratification 

 of the sandstone mostly corresponds closely with the slopes of the in- 

 terior and exterior surfaces, changing from very stee[) to nearly horizon- 

 tal as we reach the foot of the butte. The lajers are, I think, more 

 regular than they would have been if deposite<l sub-aerially, in the 

 midst of rain; and I am, on the whole, strongly impressed with the 

 belief that the eruption and deposition were sub-aqueous, and took place 

 when this whole plain was covered by the waters of a lake. A small 

 secondary crater, from 200 to 300 feet across, was noticed on the crest 

 of this cone near the northwest corner. The main crater opens toward 

 the southeast ; but no lava-stream was found there. The more southern 

 cone was Aisited by Mr. Bechler, who reports its crater as rather larger 

 and not quite so deep as that just described. The two cones are united 

 at the base, and their combined deposits make something of a platform 

 about them. This is more or less washed up to about 50 or 00 feet, as 

 though the waters had been for some time pouded about their base, and 

 waves had been dashed against them. This erosion has separated some 

 masses of the sandstone from the platform. One of these, in approach- 

 ing from north or south, made a prominent feature of the landscape, and 

 "was named, by Mr. Adams, "Kenilworth Castle," from a supposed re- 

 semblance to those famous ruins. The sandstone is irregular in its degree 

 of solidity, and has weathered out into chamber-like hollows, sometimes 

 reaching far enough in to make comfortable shelters, some of which have 

 evidently aiforded temporary protection to Indians, while others are 

 partly iilled with accumulations of sticks forming the beds of wild 

 beasts. The weathering has, in some places, worn passages completely 

 through projecting masses, which thus take the form of Hying buttresses. 

 Under the eastern overhanging side of this block, there were numerous 

 rude carvings, representing men, horses, bisons, cranes, jack-rabbits, 

 bears' claws, &c., evidently cut by Indians in recent times. The rock 

 •weathers away too rapidly to allow us to attribute any great anti(iuity 

 to these figures. They are evidently only the scratchings of an idle 

 hour. This fragile sandstone apparently never continued across the 

 "western channel to the basalt-terrace ; and from this fact, as well as from 

 the indications alread;s^ named, I infer that the valley in the basalt-plain 



