CHAPTEE XII. 



PROSPECTING. 



Methods of prospecting in mines southeast of the compromise line. The method of pfOSpeCt- 



ing adopted by the superintendents of the mines on Ruby Hill has been 

 somewhat different in the two regions which are separated by the compro- 

 mise line. This line, which was adopted by the Richmond and Eureka 

 companies as a boundary line between their respective claims, seems also to 

 have been a natural division, as the ground on either side of it in the belt 

 of mineral limestone exhibits somewhat different structural features. This 

 difference has been fully explained in the chapter on the structure of Ruby 

 Hill. The fact that most of the bodies of ore found during the earlier 

 workings lay near the quartzite in the mines southeast of the compromise 

 line, caused the adoption of a method of prospecting which consisted in 

 sinking perpendicular shafts in the limestone, driving cross-cuts to the 

 quartzite, which was called the foot wall, and running levels along the con- 

 tact of that rock and the limestone. When this contact was not so irregu- 

 lar that the drifts became longer and more expensive than the advantages 

 of a clay seam warranted, the levels were kept close along the quartzite, 

 and cross drifts were run off into the limestone where indications were 

 favorable for finding ore. Where the course of the quartzite face was too 

 irregular the levels were driven near it parallel to its general direction. To 

 define exactly what the Eureka miner considers to be "indications'' is a 

 difficult task. Fissures and seams, crushed, broken, and brecciated lime- 

 stone, limestone stained with ferric oxide, and caves are considered to be 

 good indications for ore — though drifts in which the country rock has shown 

 all these phenomena have often developed nothing. On the other hand, no 

 ore bodies have been found which, on one side or another, do not exhibit 



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