78 THE CANADIAN NATURALIST. [Vol. viii. 



or Sherman's Patent). The principle of these jiggers is that there 

 is a piston box divided into two compartments connected with 

 others in which there are sieves, and over these the water laden 

 with powdered rock flows. A downward sharp motion is com- 

 municated to the pistons which forces the water to rise up 

 slightly through the sieve-boxes, on which the heavier and coarser 

 material has settled, thus loosening it. By this means the finer 

 particles of the heavier rock and copper pass through the sieves 

 into the compartments below, whence they are washed down and 

 are farther separated on other sets of jiggers. But the larger 

 portion of the finer rock is carried off the sieves with the over -flow 

 of water. By continuing this operation a mineral of rO to 88 per 

 cent, of copper is obtained in small grains. The refuse from the 

 jiggers is worked over on percussion-tables and in tossers, or else 

 on convex or concave (English) baddies, by means of which au 

 additional quantity of fine copper is saved. At best 20 to 40 per 

 <?eut. of all the copper is lost in the concentration, the larger loss 

 being caused by the particles of metal being more or less flaky. 

 For some distance about the stamp-mills the water in the 

 lake below has a copper color, derived from minute particles of 

 the metal held in suspension. 



Three different kinds of stamps are used on the Keweenaw 

 Peninsula. The first is the square headed stamp weighing from 

 .900 to 1100 pounds, and falling 16 to 18 inches by its own weight, 

 four heads working in each battery, which is cap tble of crushing 

 12-14 tons of rock in 24 hours. The second kind is B ill's p itent 

 stamp, the shoes of which are oval. Together the heads and 

 shafts weigh from 2000 to 2200 pounds, the whole being lifted two 

 feet and forced dowu by a high pressure of steam in a cylinder 

 at the upper end of the shaft, and in the meanwhile the st imps 

 are made to revolve. Each stamp is capable of crushing more than 

 100 tons of rock per day (24 hours). The third kind is the atmos- 

 pheric stamp, of which there are six heads to a battery. To each 

 stamp there are engine fittings just above the shoes, for compres- 

 sing the air, and all six are attached to cranks on a common 

 .shaft. Although each stamp complete weighs only 200 to 300 

 pounds, the quantity of work done per day is comparable to that 

 accomplished by Ball's stamp under the same amouut of steam. 

 The shoes are usually made of white iron, and last six or 

 seven days with Ball's stamp, while with the others they last 

 21 to 30 days before being worn out. Each of those of Ball's 

 patent is allowed 20 jiggers. 



