GEOLOGY OF THE EUREKA DISTRICT. 



BY ARNOLD HAGUE. 



CHAPTER I. 



GENERAL DESCRIPTION. 



The Eureka District is situated on the Nevada plateau in the central 

 part of the state of Nevada, midway between the basin of Lake Lahontan 

 westward and the basin of Lake Bonneville eastward. The area covered 

 by the geological and topographical survey embraces a region of country 

 20 miles square, lying partly in the county of Eureka and partly in the 

 county of White Pine. 



The meridian of 116 west from Greenwich passes just westward of 

 the center of the examined area, and the 39 30' parallel of north latitude 

 crosses Ruby Hill, the seat of the present activity in precious-metal 

 mining. 



Nevada plateau. On the Nevada plateau the broad central north and 

 south valleys, lying between meridional mountain ranges, reach an aver- 

 age altitude of 6,000 feet above sea-level, the country falling away grad- 

 ually on both sides till at Salt Lake, in Utah, the altitude is 4,250 feet, and 

 at Carson and Humboldt Lakes, in Nevada, 3,800 feet above sea level. 

 These valleys, however, compared with those of the depressed areas adjoin- 

 ing the plateau, are relatively narrow, with few marked exceptions, seldom 

 measuring more than 10 or 12 miles in width. In general the broader 

 physical features of the Great Basin ranges are much the same all the way 

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