No. 6. J DOUGLAS — LAKE SUPERIOR COPPER MINES. 325 



ton, are broken. Such blocks require enormous force to shiver 

 them, inasmuch as they are generally permeated with metallic 

 copper in arborescent masses, which so binds the rock together, 

 that even when broken, fresh force has to be used to drag the 

 detached stones asunder. In the ore houses a preliminary hand 

 sorting of the rock takes place before it is further reduced in size 

 by Blake's crushers. Beneath the Blake crushers, other hand 

 pickers are stationed, who separate still more of the barren or 

 almost barren rock; and the ore, reduced in quantity to about 

 two-fifths of what was hoisted out of the mine, is run down the 

 steep inclined tramway to the copper house. 



Stamps are used invariably throughout the peninsula for crush- 

 ing the ore. Cornish rolls have been tried, but without benefit. 

 They become so often clogged with the larger lumps of copper, 

 and, thus kept apart, so much stuff passes through uncrushed, 

 that the quantity of raff was enormous, and the yield of the rolls 

 small. In the Quincy Mill, when running to its full capacity, 

 70 square shafted stamps, weighing 900 lbs. each, and with a 

 drop of 16 inches, crush 232 short tons of rock, or 33 tons per 

 stamp head per diem through screens perforated with ^-incli 

 holes. Two of the batteries are engaged upon the barrel work, 

 w^hich is, by their pounding action, more perfectly freed from 

 rock than it can be in the ore-house, but has, of course, to be 

 removed from the battery-box ; and all the battery-boxes have to 

 be cleaned out twice a day. From the batteries the ore passes 

 on to shaking sieves perforated with ^-inch holes, and fine and 

 coarse are further classified before being concentrated by enter- 

 ing with a full stream of water a succession of long triangular 

 troughs which diminish in diameter and depth as size after size 

 is drawn off to its proper hutch. The hutches everywhere used 

 are piston hutches with fixed bottoms; and though in different 

 mills they go under different names, the differences are in reality 

 trifling. Collom's jigs are those most commonly used, and con- 

 sist of a central piston-box divided into two compartments, each 

 of which is in communication with an adjacent compartment in 

 which the sieve is fixed and into which the copper that passes 

 through the sieve falls. The pistons of the twojiutches are pres- 

 sed down by a single rock shaft, and each piston is lifted back 

 into position by a f^pring — a desirable motion — as the down stroke 

 is thus sharp and rapid, and the up-stroke slower. But the 

 hutch is open to the objection that, as each piston covers only 



