260 



MINING mDUSTEY. 





November, 1866. 



December, 1866. 



January, 1867. 



Tons worked 



















120 



148 



314 





Gold. 



Silver. 



Total. 



Gold. 



Silver. 



Total. 



Gold. 



SUver. 



Total. 



Assay value per ton .... 



$11 85 



$49 59 



$61 44 



$12 73 



?53 92 



$64 65 



$10 54 



§42 77 



§53 31 



Yield per ton 



6 40 



23 12 



29 52 



S 75 



19 59 



25 34 



4 36 



12 88 



17 24 



Proportion of gold and silver — 



19-3 



80.7 



100. 



19. 1 



80.9 



lOO.O 



20.0 



80.0 



lOO.O 



in assay value of tailings. 





















Proportion of gold and silver 



21.7 



78.3 



100.0 



22.7 



77-3 



100. 



2S-3 



74-7 



100. 



in bullion. 





















Percentage of gold and silver 



S4-0 



46.6 



. - 



45-2 



36-3 





41-3 



30.1 





extracted. 

 Yield per cent, of assay value 





















48 





38 





32-4 



Various other contrivances for concentration have been introduced into 

 the district, but none, so far, have come into general use. 



Among other noticeable machines for this purpose is Hunter's concen- 

 trator, which has been used for several years in California, and which the in- 

 ventor sought, about a year ago, to apply successfully to Comstock tailings 

 This is a percussion table of small size, being about 30 inches long by 24 

 wide, so suspended in a frame-work as to admit any desired inclination and 

 the slight movement imparted by the percussion. The bottom of the table 

 is slightly inclined from each end toward the middle. The tailing end is 

 usually placed about an inch lower than the head. The material is supplied 

 by a distributing launder about 8 inches from the head and, close by it, nearer 

 the head, is a launder supplying clean water, which, like the material to be 

 concentrated, is fed through a series of holes, so as to distribute it evenly 

 across the table. The percussion is applied at the lower end of the table, 

 at the rate of 200 to 240 shocks per minute. Its effect is such that the 

 denser particles are sent toward the head in resistance to the stream of 

 water, while the lighter particles yield to the force of the water and are car- 

 ried down to the lower end and discharged. The separation therefore takes 

 place at the point of supply, the heavier particles moving in one direction and 

 being discharged at the head, the hghter sand moving with the water to the 

 lower end and discharging there. A revolving scraper, just touching the sur- 



