40 



GEOLOGY OF THE EUREKA DISTRICT. 



range, both in silica and magnesia. Two complete analyses were made of 

 this limestone, one from the summit and the other from the base of the 

 epoch, each representing a well denned and persistent bed, as follows: 



Aii examination made of a dark compact limestone from the base of 

 the Hamburg, collected on the north side of the ravine opposite the dump 

 of the Richmond shaft, gave 



Silica -84 



Carbonate of magnesia 1-18 



A gray dolomite from the 350-foot crosscut in the Dunderburg mine 

 yielded 



Silica -07 



Carbonate of magnesia 40-04 



lu general, this limestone is sharply contrasted in its lithological habit 

 with the Prospect Mountain body, as it is darker in color, carries siliceous 

 material in place of the clayey beds of the latter, and possesses a character- 

 istic rough and ragged surface produced by weathering. The thickness of 

 this limestone may be taken at 1,200 feet, and except in the shaly lime- 

 stones at the top and bottom of the series, 110 planes of bedding are trace- 

 able for any great distance. At Adams Hill, however, where the beds lie 



