122 WALKS AND TALKS. 



\vas struck at 3,080 feet. All the data together indicate an 

 increase of temperature of one degree for 28 feet of depth. 

 This abnormal increase appears confined to the vicinity of the 

 lode. The great Sutro Tunnel, which approaches the east 

 wall at a depth of 1,900 feet, indicates a great increase of 

 temperature in approaching the wall. At the distance of 128 

 feet, the temperature is 110; at 1,048 feet, 108; at 2,052 

 feet, 96; at 3,651 feet, 89; at 5,008 feet, 87; at 7,175 

 feet, 85; at 9,512 feet, 83; at 10,849 feet 79. This great 

 increase of temperature can not be attributed to the increase 

 in depth of the tunnel below the earth's surface. The ex- 

 traordinary temperature, therefore, is a phenomenon of the lode. 

 It appears to rise from some greater depth, and the indications 

 point to ascending water as the probable agent in bringing up 

 the heat from a deeper region. It acts, therefore, like an 

 enormous hot spring. Thirty miles away is the Sierra Nevada 

 range, and from the altitude of perpetual snow, the eastward 

 dipping strata descend into the earth for a great depth. The 

 water which accompanies them reaching the deep portion of 

 the Comstock Lode, their course is in part arrested by the 

 impervious clays. When reached therefore by the mining 

 operations, the relief of pressure causes them to rise from 

 depths much below the bottom of the works. 



The waters just mentioned constitute the second powerful 

 obstacle to mining on the lode. In the deeper works, the 

 volume has assumed portentous proportions. The water was 

 originally pumped to the surface through the vertical shafts. 

 Steam-pumps of ever increasing capacity, however, proved 

 successively inadequate to the demand. Hence, the daring 

 enterprise of Adolf Sutro conceived the tunnel which bears 

 his name, and which, through thirteen years of opposition, he 

 fought to successful completion in 1878, at a cost of two mil- 

 lion dollars. The outlet of the tunnel is 20,000 feet from the 

 east wall of the lode. From the entrance, a lateral branch is 

 extended north along the lode 4,403 feet (to October, 1880), 

 and another lateral, southward, 4,114 feet. The tui.nel is 

 seven feet in height, and eight feet in width in the clear, with 



