252 MINIifG INDUSTEY. 



SECTION IV. 



TEEATMENT OF SLIMES AND TAILINGS. 



The treatment of the residue, or that which remains of the ore after it 

 has been subjected to the process already described in this chapter, is a mat- 

 ter of much importance. In the earher years of operation on the Comstock 

 lode but little attention was paid to the stream of tailings that was constantly 

 flowing from the mills, carrying wifch it a considerable proportion of the orig- 

 inal value, because it was generally assumed that the first process had ex- 

 tracted from the ore everything that could be obtained with a margin of profit 

 above the costs of milling; but with the gradual improvement in methods of 

 work and the reduction in costs of operation, the attention of mill-men has 

 been generally turned to this subject. 



Frequent reference has been made, in the course of this chapter, to the 

 character of these residues, the way in which they are produced, and their 

 value as a source of profit to the mills engaged in reducing the ore. 



It may be repeated that the term "slimes" applies to that portion of the 

 crushed ore which is reduced by the stamps to an exceedingly fine condition 

 and, flowing from the batteries in the stream of running water, does not find 

 sufficient opportunity to deposit itself in the tanks in which the coarser sands 

 are collected, but is carried beyond them, and only settled, after a long time, 

 either in another set of tanks or in large reservoirs. These are properly called 

 "battery slimes," to distinguish them from the material that may be reduced 

 to a similarly fine condition by the operation of the pan. 



The term "tailings" is understood especially to apply to that portion of 

 the crushed ore which, after having been subjected to the grinding and amal- 

 gamating process in the pan and settler, flows away from the latter, or from 

 the agitator, and passes on out of the mill, deprived of the greater part of its 

 valuable contents. A part of this material is in a very fine and slimy condi- 

 tion, but the bulk of it may be better described as a fine-grained sand. Leav- 

 ing the mill the stream flows onward, and is usually subjected at once to 

 various methods of concentration, the most common of which is the blanket- 

 table, by which means a portion of the escaping amalgam, quicksilver, and 

 heavier particles of ore may be extracted to be reworked, while the great mass 



