152 GEOLOGICAL SURVEY OF THE TERRITORIES. 



has apparently cut its Tvay directly through one of the great limestone 

 ranges, and abruptly flexes arouud and flows southward. The river cuts 

 the end of the mountain-range that extends up in the bend, so that the 

 north end forms a high, precipitous mountain wall. The river runs 

 through a deep gorge of basalt. On the opposite side there is a steep 

 wall of limestone 800 to 1,000 feet high. The passage from Upper 

 Port I^euf to Upper Bear Eiver Yalley is a narrow gateway about half 

 a mile wide. The general trend of all these ranges is nearly northwest 

 and southeast J the inclination of the limestones 15^ to 30^, though in 

 some exceptional cases extensive groups of strata incline as high as 60^. 



The high range, which can be seen so distinctly extending far south- 

 "ward from Soda Springs within the bend, is on'y a portion of the im- 

 mense limestone range seen on the east side of Cache Valley as we jour- 

 neyed northward in June. It is entirely composed of the old quartz- 

 ites and underneath them the well-defined Carboniferous limestones, as 

 shown in the Wahsatch Kange, the limestones and the quartzites again 

 overlying the limestones. I could not discover any traces of the usual 

 metamorphic group. There is a broad belt of country lying between 

 the drainage of Snake and Green Kivers, which is formed of a series of 

 folds in the crust, that have not yet been worked out in detail. In all, 

 this belt it is seldom that rocks older than the Carboniferous are ex- 

 posed. 



At the bend of Bear Eiver, is located the most interesting group of 

 soda springs known on the continent. They occupy an area of about 

 six square miles, though the number is not great. At this time they 

 may be called simply remnants of former greatness. Numerous mounds 

 of dead or dying springs are scattered everywhere, and onl^^ a few seem to 

 be in active operation. So far as the manner of building up the calcare- 

 ous mounds is concerned, it does not difler from that of the hot springs 

 in the Yellowstone Valley, and it may be that they were boiling springs 

 at some period in the past. At the present time they are not usually much 

 above the temperature of ordinary spring- water. In one or two instances 

 the active springs were found to be luke-warra. Nearly all tbe springs 

 were in a constant state of more or less agitation from tiie bubbles of 

 gas that were ever escaping. In a few cases the water is thrown up 2 

 to 4 feet. One spring with a basin 10 feet in diameter, with the surface 

 covered over with bubbling points from carbonic acid gas escaping, had a 

 temperature of 61Jo ; another bubbling spring, 05^. The Bear River 

 cross-cuts a number of the mounds, tbus revealing the secret of their 

 structure. The mounds vary from a few feet to twenty or thirty feet 

 high, built up, in the same way as the hot-spring cones, by overlapping 

 layers. There are many of these mounds, which show, by the steepness 

 of the sides, the amount of hydrostatic pressure. Many of the chim- 

 neys are nearly vertical, with the inner surface coated over with a sort 

 of porcelain. At one point on the margin of Bear Eiver there are two 

 steam- vents, from which the gas is constantly escaping with a noise 

 like a low-pressure engine. Near the edge of the river there is a beau- 

 tiful spring with a chimney about two feet in diameter lined inside and 

 out with a bright-yellow coating of oxide of iron, in which the water is 

 thrown up two feet by a constant succession of impulses. The inner por- 

 tions of the chimney are lined with the porcelanic coating as smooth 

 as glass, and tinged through with a bright yellow from its iron. Near 

 the foot of the hills, a mile from the river, there is a soda-spring, with 

 a mound about 10 feet high, with a large rim 30 by 100 feet, but with 

 a small quantity of water compared with what formerly flowed from it ; 

 temperature, 53Jo. Near this spring are a number of large springs 



