174 GEOLOGICAL SURVEY OF THE TEKEITOEIES. 



made of the finely pulverized dust of volcanic rock, and is covered with 

 a sparse growth of sage-brush. The river is bordered with a growth of 

 thinly scattered pines and quaking-asps. In the mountains, on either 

 side, are stratified limestones, which rest on the gneissoid rocks we 

 observed in the canon. Scattered over the hills and through the valleys 

 I found many beautiful specimens of chalcedony and chips of obsidian. 

 Many of the chalcedonies were geodes, in which were crystals of quartz ; 

 others contain opal in the center and agate on the exterior ; and still 

 others have on the outside attached crystals of calcite. A short dis- 

 tance above the caiaon we came to Cinnabar Mountain, so named from 

 the color of some of its rocks, which have been mistaken for cinnabar, 

 although the red color is due to iron. Here we encountered what is called 

 the Devil's Slide. It consists of two masses of rock in almost vertical 

 position, perfectly defined as two walls. They are about 50 feet in 

 width each, and 300 feet high, reaching from the top of the mountain to 

 its base. They are separated from each other about 150 feet, the inter- 

 vening softer material having in the lapse of time been washed away. 

 The right-hand mass is a whitish quartzite, while the left-hand 

 one is a dike of greenish i^orphyritic trachyte in which the crystals 

 of feldspar are thickly disseminated. Parallel with these two principal 

 walls are many more ridges of quartzitic and slaty nature, none of which 

 equal them in magnitude. They are all nearly at right angles to the 

 strata of limestone, which lie on either side. In a space to the right, 

 of the main ridge there is a broad red band reaching from the top to 

 the bottom of the mountain. It is caused by the sliding of ferruginous 

 limestone and clay. It is about 20 feeb wide and distinctly outlined. 

 These ridges must have been forced into their present position when the 

 strata above were horizontal. That there has been a terrible 

 convulsion here in the past is i^roved a few miles farther on, where the 

 strata of limestone are so contorted that, within the space of 200 feet, 

 they dip in three different directions. In the limestone there was an 

 abundance of crystals of calcite. Some eight or ten miles farther on 

 we reached Gardiner's River, a stream emptying into the Yellowstone 

 just as the latter emerges from a caSon. Here we left the Yellowstone 

 to visit some hot springs about four miles above the junction of the 

 two streams. We soon came to the evidences of hot springs in the 

 calcareous deposit, beneath which the warm water escaped into the 

 river. Passing a number of hot springs, we began the ascent of a steep 

 hill, passing over the deposit, which gave forth a hollow sound beneath 

 our horses' feet. Suddenly we came in full sight of the springs. We 

 were totally unprepared to find them so beautiful and extensive. Be- 

 fore us lay a high white hill, composed of calcareous sediment deposited 

 from numerous hot springs. The whole mass looked like some grand 

 cascade that, had been suddenly arrested in its descent, and frozen. On 

 exauiiuatiou we found that the deposit extended for some two miles 

 farther up the gorge, and below reached to the edge of the river, occu- 

 pying altogether about three square miles, although the greater part 

 of it is now in ruins and overgrown with innes. Still the outlines can 

 be very distinctly traced. The principal mass is arranged in a series 

 of terraces, one above the other, each being composed of beautiful 

 basins^ semicircular in shape, and having regular edges, with exquisitely 

 scalloped margins. Their size varies, but will average 5 by 8 feet. 

 They are filled with water of different temperatures, from cold to tbe 

 boiling-point. The color of the sedimefit is for the most part white, al- 

 though here and there are tinges of yellow where sulphur predominates, 

 and red and pink where there is iron. The weathering of those parts 



