32b EXPLORATIONS ACKOSS THE GREAT BASIN OF UTAH. 



As none of the crystals have both ends perfect, I could not ascertain whether they 

 are hemihedrally developed, as is most common with the topaz, or have both ends alike. 

 Its pyro-electricity was not examined, nor the polarization of light, but the crystals 

 show very plainly the double refraction. 



I will conclude this paragraph with a passage from a letter of Colonel Fremont to 

 the National Intelligencer, dated June 13, 1854, and afterward printed by order of 

 Congress (33d Congress, 2d session, Mis. Doc. No. 8). Colonel Fremont crossed the 

 Wahsatch range near Para van and Cedar City, and to these points his, perhaps a little 

 too highly colored, observations refer : "They are what are called fertile mountains, 

 abundant in water, wood, and grass, and fertile valleys, offering inducements to settle- 

 ments. The mountains are a great store-house of materials, timber, iron, coal, which 

 would be of indispensable use in the construction and maintainance of the (Pacific) 

 railroad, and are solid foundations to build up the future prosperity of the rapidly 

 increasing Utah State. Salt is abundant on the eastern border; mountains, as the Sierra 

 de Sal, being named from it. In the ranges lying behind the Mormon settlements, 

 among the mountains through which the line passes, are accumulated a great wealth 

 of iron and coal, and extensive forests of heavy timber. These forests are the largest 

 I am acquainted with in the Rocky Mountains, being in some places 20 miles in depth 

 of continuous forest; the general growth is lofty and large, frequently over 3 feet in 

 diameter, and sometimes reaching 5 feet, the red spruce and yellow pine predominating. 

 At the actual southern extremity of the Mormon settlements, consisting of the two 

 inclosed towns of Paravan and Cedar Cky, near to which our line passed, a coal-mine 

 has been opened for about 80 yards, and iron-works already established. Iron here 

 occurs in extraordinary masses, in some parts accumulated into mountains, which comb 

 out m crests of solid iron thirty feet thick and a hundred yards long." 



GEOLOGICAL STRUCTURE OF THE SUCCESSIVE MOUNTAIN RANGES. 



In the Wahsatch Mountains, on crossing Weber River from the east, on the road 

 between Fort Bridger and Camp Floyd, we enter the district which I have comprised 

 m section V. The main body of the divide between Weber River, Silver Creek, and 

 Timpanogos River, is composed . .f diorhic porphyries, which I have described under the 

 heading ot igne, >us rocks. Near Kansas Prairie, the rocks exhibit a more lavatic appear- 

 ance, but probably belong to the same group. These igneous pn rtrasiona may be regard- 

 ed as the center of the range. East of them we find more recent stratified rocks, while 

 on the west side the mountains appear altogether composed of strata of the Paleozoic 

 formation. On Weber River, and on the Timpanogos, above Round Prairie, con- 

 glomeratic tufas were noticed, made up of these eruptive rocks, imbedded in a' finer 

 material of the same origin. These masses have either been deposited in water, or 

 became at least cemented and indurated by its agency. 



The interesting warm springs of Round Prairie, and their formation of calcareous 

 tutii. have been described above. ' 



Near the north end of Round Prairie, the first stratified rocks of this section were 

 observed, tilted by the porphyries. These are mostly light-colored, anda fewreddish 

 sandstones, a siliceous limestone, and some red, shah" strata. Their age is probably 



