PEOSPECTING. 149 



the greatest care. And as many assays as convenient should be made in 

 order that local differences in the rock should be rendered as small as 

 possible. In running a drift, it would be well to take four assays per day, 

 which might be used separately or averaged. Care should be taken to 

 exclude all seams containing traces of ore, which can be assayed separately 

 if desired, as it is the enriching of the country rock itself that it is necessary 

 to observe." 



Great caution should be employed in making use of these assays and 

 the results should be carefully compared with other indications in the 

 country rock and the general structure of the ground. With proper pre- 

 cautions the assaying of the country rock will in many instances become 

 an important aid to the miner. The method is better adapted to the dis- 

 covery of large and irregular bodies of ore in a formation similar to that 

 in Eureka than it is to the search for small, though rich veins. 



"The methods used in assaying the Eureka ores are fully explained in Chapter XI. 



