GEOLOGICAL SURVEY OF THE TERRITORIES. 61 



tion of the Gallatin rauge iu a subsequent chapter, where other exam- 

 ples of iuversion of strata will be noticed. 



About ten miles northwest of Lake Henry, below the Middle Canon, a 

 small stream, which has its origin in the Rayuold's Pass, flows into Clifi' 

 or Wade's Lake.* The little stream has cut a singular gorge through the 

 trachyte-rocks, with vertical walls 400 to 000 feet high, runs southwest 

 about two miles, turns abrui)tly south around a point of trachyte 000 feet 

 high, and continues nearly west. This lake, which has not been noticed 

 on any of the existing maps, is said to have no outlet. It seems to be 

 formed in a huge fissure iu the volcanic rocks, and is surroundetl b\' 

 lofty nearly vertical walls. 



This lake was carefully explored by Mr. Bechler, and the beautiful 

 map of it, accompanying this report, was prepared by him. He says 

 that it has three small streams flowing into it, but has no visible outlet, 

 but the surplus water probably passes under the basaltic cap. The sides 

 of the lake are so steep and high that it is not possible to travel near 

 the shore, but Mr. Bechler ascended the high cliffs overhanging the lake 

 and obtained a beautiful view of the surrounding scenery. The high 

 basaltic clifits that inclose it suggested the name of Cliff Lake. Near 

 the middle of the lake, there is a small, conical island, about 150 feet in 

 diameter, but rising 100 feet or more, covered with tall, straight pines. 

 There were several smaller lakes iu the vicinity, all of them a[>pareutly 

 formed iu these basaltic fissures, and without any visible outlet. 



The valley below the Middle Caiion gradually exi)ands until it 

 becomes six to ten miles in width. At the upper end of the valley the 

 terraces do not show as well as below, but in no other portion of the 

 West have I seen so uniform and so beautiful a series of terraces as in 

 this basin. I point this out here to the reader, who may ever chance to 

 visit the country, as one of the wonders of this remarkable region. At 

 the upper end of the basin the terraces are quite well defined and show 

 a most extensive deposit of loose material at the bottom of the lake. 

 The surface of the entire valley is covered with bowlders of greater or 

 less size, many of them huge massive granite. On both sides of the 

 river are caps of basalt covering and protecting from erosion the under- 

 lying lake deposits. From these basalt-capped hills or terraces I infer 

 that the modern lake-deposits must have originally been from 500 to 800 

 feet thick, perhaps much more. The river has cut its way through this 

 deposit, forming in some instances a narrow gorge with the basaltic 

 cap on either side like a high terrace, while the foot of the mountains 

 on both sides is distant from half a mile to one mile. We can thus 

 understand pretty clearly what must have been the thickness of these 

 lake-deposits immediately after the outflow of the igneous matter. As 

 we pass down the river all this basaltic floor has remained, and the 

 entire surface of the valley, from side to side, smoothed like a lawn. 

 Whether there was one period or several of outflow of basalt I cannot state 

 positively. In the verticalsidesof the river-channel the basalt may be seen 

 at different elevations, but no continuous layers, and, therefore, it may have 

 fallen down from the summit; yet I suspect there were several periods 

 of outflow. In many localities the basalt is exposed in the form of a 

 high vertical wall with a partial columnar appearance. It also varies, 

 in color as well as in texture, from a very dark-brown to a purplish-drab. 

 All the lake-deposits, as well as the igneous rocks, lie iu horizontal po- 

 sition, and, so far as can be observed, have not been affected by any 

 subsequent movements. We may, therefore, infer that the forces which 

 raised the surrounding mountains to their present position, and tilted 

 the stiata, operated prior to the existence of these fresh- water lakes. 



