GEOLOGICAL SURVEY OF THE TERRITORIES. 47 



to tbe summit, thousands of beautiful springs of water gush out, and, 

 concentrating in some valley, form quite large streams, and really are the 

 main sources of these rivers. Sometimes these ridges are only a few 

 feet in width at the summit, as between the waters of the Muddy and 

 the east branch of Bear River. Here a little further up' the mountain 

 it expands out to a width of four to six miles, and is covered with 

 large forests of pine and aspen groves, with meadow-like openings, 

 varying in size from fifty to one thousand acres each. Then again, 

 to the sources of the main branches near the mountain crest, these 

 ridges become very narrow, merely separating the waters of the 

 streams. Upon these ridges are trails or roads, made by men or wild 

 animals, which lead one with comparative ease up the rugged mountain 

 divide. Spruce Eidge is formed of a great thickness of drift conglom- 

 erate. This consists of quite large masses of purplish and gray sand- 

 stone, quartzites, and carboniferous limestones with fossils, with now 

 and then a granitoid or gneissic rock. The boulders are not usually 

 large, varying in size from a small pebble to two feet in diameter. The 

 rocks are mostly the purplish sandstone, quartzites, and limestones from 

 the carboniferous ridges. These rocks are more or less water-worn 5 

 some of them are quite angular, as if they had not been transported far 

 or rolled in the waters, others are much rounded. They are set in an 

 arenaceous pudding-stone paste, mostly decomposed feldspar and quartz 

 of a grayish-white color. The whole mass is not closely cemented and 

 yields readily to atmospheric agencies. The entire thickness of this 

 modern deposit, as shown by this ridge, must be very great, from four hun- 

 dred to eight hundred feet. It, however, varies much in thickness in differ- 

 ent portions of the range. I have mentioned the different kinds of 

 rocks in this ridge from the fact that such deposits are almost certain 

 to contain specimens from all the geological formations which come 

 within the scope of the agencies which deposited it. I have found by 

 experience that I can anticipate the existence of nearly all the rocks of 

 different formations or those of different ages, in a mountain, by examining 

 the drift materials distributed over the base or foot-hills of the range. 

 This ridge also presents a marked illustration of the influence of laud- 

 slides in shaping the surface of the sides of this range. These slides 

 are doubtless caused by the numberless springs which ooze out of the 

 sides at every point of elevation from the plains to the main divide. 

 They also give the peculiar, terrace-like, or step-like character to the slopes 

 which has suggested the name of " terrace range" for these mountains. 

 These steps are usually very gradual and smooth, but in some cases they 

 give an extreme ruggeduess to the surface. The east side of Spruce 

 Eidge is nearly vertical for two hundred feet or more, and the conglom- 

 erate beds project out of the sides in horizontal layers. The east side is 

 very steep, but slopes down to the plains without any very abrupt break, 

 and is covered with grass or forests of aspen or inne ; but the west side is 

 covered, as far as the valley of Bear Eiver, with a series of abrupt steps, 

 which would appear to be of comparatively modern date or of different 

 dates within our present period. These landslides, on the west side of 

 this ridge, extend a width of three to five miles before reaching the east 

 branch of Bear Eiver ; and from the summit of this ridge we had a most 

 excellent opportunity to study the effects. An immense mass of the drift 

 conglomerate has slipped off from the ridge and fallen down ; the detached 

 mass opposite the main ridge is the highest, forming a sort of sharp, low 

 ridge, sloping toward a depressed center; thus a depression is made for 

 the accumulation of waters from the drainage of a small area ; and thus 

 others — most of the little lakes that have given such celebrity to these 



