1874.] Copper Mines of Lake Superior. 169 
‘shore mines to calcine the rock, and thus render it more 
friable ; but following the example of the Calumet Mine, a 
hammer like a pile driver has been introduced into the 
Quincy ore-house, which reduces the larger blocks to a size 
suitable to the Blake crusher, and for hand-picking. The 
ore undergoes the following treatment. Discharged from 
the hoisting car, it is carried down an incline to the ore- 
house, which is on the brink of the steep hill overlooking 
the lake. The ore-house is provided with a hammer, under 
which, as stated, the largest blocks, weighing often over a 
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 
crushing 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 goo lbs. each, and with a drop of 16 inches, 
crush 232 short tons of rock, or 3°3 tons per stamp head per 
diem through screens perforated with 4-inch holes. Two of 
- the batteries are engaged upon the barrel work, which 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. [rom the batteries the ore passes 
on to shaking sieves perforated with 23-inch holes, and fine 
and coarse are further classified before being concentrated 
by entering 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 consist of a central piston- 
