326 THE CANADIAN NATURALIST. [Vol. Vli. 



half the corresponding sieve, a wave is propagated from one end 

 of the sieve to the other, which interferes with the regular sub- 

 sidence of the ore. As the ore is imperfectly sized, some collects 

 in the sieve and is removed from time to time, but most falls 

 into the bottom, whence it is carried away by the flow of water. 



The hutches are arranged, with a view to saving labour, in 

 tiers one below the other, so that the scimpings from one flow 

 into a hutch on a tier below, and the concentrate is re-concentra- 

 ted in like manner. Water being the carrier, no handling, or 

 very little, is required from the time the ore is thrown into the 

 stamps till it is shovelled from the receiving tank as 80 to 90 per 

 cent copper. 



One of the most perfect mills on the lake shore is that of the 

 old South Pewabic mine — now the Atlantic. In it, the stuff 

 crushed by Ball's stamps is concentrated by 112 hutches arranged 

 in seven tiers. There, also, the rotating German huddle is found 

 to save the copper from the slimes effectually and cheaply. In 

 the Quincy Mill, the old-fashioned percussion-table takes out the 

 coarse slimes, and tributers re-treat the refuse from the whole 

 mill in a separate building with English buddies. The coarse 

 concentrate generally runs to nearly 90 per cent of copper, the 

 fine, which cannot be separated, without repeated washing, from 

 the iron — which we have seen is a constituent of the trap matrix 

 — sometimes stands as low as 50 per cent; but all the mills aim 

 at delivering an average of 80 per cent to the smelting works. 



Side by side with the Quincy Mill is the Pewabic Mill, in 



which Ball's stamps are used. A comparison of the tailings from 



the two mills, made by Mr. Macfarlane, is interesting. He found 



Quincy Mill. 



Scimpings from coarse ragging 006 per cent 



IScimpings from fine ragging 0-73 " 



Buddie tailings 0-46 



Pewabic Mill. 



From head of run 4-93 per cent. 



" middle of run 3-00 " 



" end of run 313 '' 



" heap outside of run-house 0-66 " 



'< sandbank 1-uO " 



The Ball stamps may influence the result, through the volume 

 of water required for their efficient working, and which, not 

 being separated from the suspended ore, may in some cases flood 

 the hutches. 



