40 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



this matter in the remarkably uuiform and compact series of strata which 

 we find at the present time must have been great. The results have 

 been carried on upon such a stupendous scale that the mind finds with 

 difQculty the courage to grapple with them or attempt to explain them. 

 And then, subsequent to the deposition of these enormous beds of con- 

 glomerates, has been the wearing-out of canons and valleys 2,000 to 

 4,000 feet in depth, the sculpturing of some of the most marvelously 

 grand and unique scenery on the continent. In passing up the valley 

 of the Upper Yellowstone, which is about three miles wide and has been 

 carved out of this hard breccia, one could easily imagine himself in 

 some enchanted land, where, on every side, were castles and palaces 

 without number. 



We may, therefore, conclude that all the surface-phenomena we find 

 here at the present time are only the insignificant remnants of the past; 

 that the lakes, streams, hot springs, &c., are only the dim departing 

 evidences of a series of events which once were performed here on a scale 

 that almost baffles human conception. The Second Canon is formed by 

 the passage of the Yellowstone Eiver between lofty walls of gneiss. 

 On the east side is Dome Mountain, a vast rounded mass of granite 

 rising 2,500 feet above the river flowing at its base. On the west side 

 are two or three rounded, naked, granite peaks, 1,500 to 2,000 feet 

 above the river, but less conspicuous. The summits and sides of these 

 granitic mountains show most distinctly the efiects of glacial action. 

 The surfaces in many places are smooth as glass, and glazed as it were, and 

 lying about loose are great numbers of rounded bowlders. The forces 

 that stripped off the thick covering of volcanic congloiherates left their 

 traces on the harder rocks below. To the westward the gneissic rocks 

 soon pass out of sight beneath the volcanic conglomerates. I shall 

 attempt to show in a subsequent chapter of this report that the gneissic 

 rocks of this canon are only a portion of the nucleus of the great range 

 which extends across the country toward the northwest to an unknown 

 distance. The mountains on either side may be said, in the main 

 to be composed of granitoid rocks as nuclei, with almost numberless 

 outflows of igneous matter. Although this statement would indicate 

 that the geological features were remarkably simple, yet the rounded 

 forms which these igneous rocks assume, and the chaotic condition of 

 the surrounding rocks produced by these volcanic movements, renders 

 the unraveling of the structure quite difficult in its details. In the 

 present report I cannot do more than present a general view of the 

 geology of the Yellowstone Valley, referring the reader to the report 

 of 1871 for more detailed information. 



The next point of importance is the Cinnabar Mountain and the so- 

 called Devil's Slide. We were enabled the past season to make a more 

 careful examination of this interesting locality, and the sketch taken on 

 the spot by Mr. Holmes is very expressive and accurate. (Fig. 5.| Cin- 

 nabar Mountain comprises a group of nearly vertical beds, rising at one 

 point 2,000 feet above the Yellowstone. The ridge, or mountain, as it 

 may be called, is about one mile in length, and in this distance are ex- 

 posed probably 10,000 feet of strata from the metamorphic quartzites 

 to the coal strata inclusive. The hard rocky strata stand up on the 

 sides of the mountain like high walls, while the intervening softer beds 

 have been washed away; the direction of inclination southwest trends 

 about northwest and southeast. The following section is given somewhat 

 in detail. It commences with the well-marked Cretaceous shaly clays, 

 which are probably Middle or Lower Cretaceous. 



