30 GEOLOGICAL SURVEY OF THE TERRITORIES. 



"between the Wind River and Sweetwater on the north. The northern 

 portion of the anticlinal is seen only for ten to twenty miles near the 

 Three Crossings, where the lower Silurian and carboniferous beds are 

 shown over a restricted area. The numerous granite ridges which are 

 scattered all through this valley are most probably remnants of a vast 

 mountain nucleus, from which the unchanged rocks inclined on either 

 side. 



We pass over a level surface for the most part, through the deep sands, 

 which are the result of the disintegration of the tertiary sandstones. 

 Large areas are covered with the alkali efflorescence, so that they are 

 white as snow. From Willow Springs we camped at Independence 

 Rock, a noted landmark for travelers for many years past. I was 

 anxious to understand the geology of this wonderful spot, and on that 

 account was delighted to find my tents pitched at its base. The Sweet- 

 water flows immediately along the southern end of it, although on the 

 opposite side of the stream another ridge continues toward the south- 

 west, which, I have no doubt, was once connected with it. Independence 

 Rock is really one of the granite ridges in this valley, and is a remnant 

 of much larger mountains. It now looks like an enormous boulder lying 

 out in the plain. It is a vast but most excellent illustration of the theory 

 of disintegration by exfoliation, for it is rounded and resembles an 

 oblong hay-stack with the layers of rock lapping over the top and 

 sides of the mass like the layers of hay on a stack. Thin layers have 

 been broken off in part, and huge masses are scattered all around it; 

 but on some portions of the sides they lap down to the ground with 

 so gentle a descent that I was able to lead my horse nearly to the sum- 

 mit, about two hundred feet. Two sets of fissures are plainly seen in 

 this rock, one set east and west and the other north and south. 



The entire mass, as well as all the granite ridges in the valley, may be 

 called feldspathic ; that is, the red and white feldspar predominate, while 

 the mica occurs in very small quantities. It is quite probable that the 

 vast quantities of this alkaline efflorescence were derived from the de- 

 composition of the feldspars. Stansbury gathered some of these salts, 

 which he called " efflorescence from a saleratus pond," on Sweetwater 

 river. Dr. Gale found them " to be composed of the sesquicarbonate of 

 soda, mixed with sulphate of soda and chloride of sodium, and is one of 

 the salts called Trona, found in the natron lakes in Hungary, Africa, and 

 other countries." These salts are not perceptible to the taste in the water 

 of the stream itself. The granite ridges south of Independence Rock, 

 and on the opposite side of the Sweetwater, I estimated to be from one 

 thousand to fifteen hundred feet above the bed of the stream. I ascended 

 one of the loftiest of the ranges, with great difficulty, on account of the 

 smoothness of the rocks and the abruptness of the sides. From the 

 summit as far as the eye could reach in every direction granite ranges 

 could be seen, of varying lengths, from one hundred to fifteen hundred 

 feet above the surrounding plains. Far away to the southeast, dimly 

 seen and overtopping all the rest, was a range of mountains which I sup- 

 pose were the Medicine Bow range. All around the flanks of these 

 granite ranges the same tertiary beds jut up without any interruption, 

 and are smooth and even, so that the granite masses seem to rise abruptly 

 out of the plains. In some of the broad intervals are the most beautiful 

 terraces or benches, sloping gently down from the base of the mountains 

 to the valley. Not a sign of water could be seen in any of these moun- 

 tains at the present time. A few cottonwoods and groups of quaking 

 asps, in some of the ravines on the sides, gave evidence that water issues 

 from them at certain seasons of the year. A few stunted pines struggled 



