2 MINING INDUSTEY. 



those of the Nevada Basin. The desert basin of Utah is still further suggestive 

 of Nevada, since the loftj Wahsatch rises abruptly from its level, scored by 

 sharp canons, closely resembling the eroded front of the Sierra. The average 

 altitude of the entire system of parallel ranges which trace themselves from 

 north to south across the Great Basin is not far from nine thousand feet. 

 The plains, from a level of four thousand feet, vv^hich is about the height of 

 the basins of Nevada and Utah, rise to a mean elevation of six thousand 

 feet in the middle of the system. 



If a circle be traced from this central point, latitude forty and longitude 

 one hundred and sixteen, with a radius of two hundred and fifty miles, the 

 circumference will be found to mark a continuous chain of depressions. The 

 middle plateau of Nevada is, then, an important center of elevation and of 

 drainage. 



The depressions of the ring are dreary reaches of desert where fields of 

 sand alternate with alkaline plains, where, in the brilliant dry air, the eye may 

 range over expanses of desolate lowland, naked and devoid of all vegetation 

 except those blighted-looking forms of life, the sages, which rather intensify 

 than relieve the deathly aspect of the scene. The central plateau region is 

 somewhat more favored; occasional grassy valleys interrupt the sage plains, and 

 the mountains are less sterile and forbidding. Trees, which were almost 

 wholly absent in the lowland, occur on the loftier ranges; and, near the per- 

 petual snow, which here and there caps the higher summits, an extraordinary 

 fertility is developed. 



A glance at any physical map of this region shows a general parallelism 

 of ridges with a prevailing northwest trend. The materials of this immense 

 mountain area are infinitely varied, ranging from the earliest to the most 

 recent deposits, and embracing almost all known species of sedimentary and 

 eruptive products. The greater part of the rock is a series of conformably 

 stratified beds, reaching from the early Azoic up to the late Jurassic period, 

 when these level beds were compressed into vast mountain corrugations and 

 elevated above the sea in a general, wide, and high plateau. Accompanying 

 the upheaval and crumphng of this great oceanic family, and bursting from its 

 fractured folds, are important masses of granite, penetrating the axes of the 

 flexures and breaking through lateral fissures. Quartz-porphyries, felsite 



