CRANE. | Economy of Mining Operations. . 357 
in connection with both the above-named substances, which 
in itself causes a waste. 
Rich ores are also more difficult to treat than lean, as the 
screens become overloaded, thus preventing a proper move- 
ment of the ore particles, and causing a waste by washing the 
ore off the screen. 
A mill fed by one or more shafts and handling 100 tons of 
ore would have a daily expense of — 
BEX a CELOMW eran peer oe maner ered enitiek cae ice yeast rr Ley Bon a $43 80 
ELOISE Crepe tay ein Me eaten teehee ge chan age aso atl oie o Senet 5 00 
CONCeENCVAtLTOMM pee ee ee ne sapere en oe shee Stave, Sucllee Mccabe! 49 43 
MO GAME TRC Ver verte cits en Sea ee os terre cate siete oe Ste $98 23 
As there are usually two shifts per day, the cost per shift 
would then be $49.11. 
The above figures are, as stated, for a mill having a ca- 
pacity of 100 tons per day; but this, as has been remarked, 
is much higher than is usual in the district. The cost for 
running a hundred-ton-capacity mill at the rate of 60 tons 
per day does not mean that the running expenses are cut 
down in proportion to the amount of material run through. 
There is little or no difference in the running expenses of a 
mill whether run at full capacity (100 tons) or at a lower 
rate, say 60 tons. The only difference in expense would be 
possibly an extra feeder, which would not materially affect 
the calculations as given above. 
Suggested Improvements. 
A careful study of the methods practiced in the Galena 
lead and zinc district shows that, in spite of painstaking ef- 
fort on the part of the mine and mill owners and operators, 
there is a large waste not only of mineral but of power. Com- 
paring the methods employed here with those in use in the 
treatment of the same and similar ores in other localities, it 
is seen that there are various processes successfully em- 
ployed by which the waste of ore and power experienced 
could, to a large extent, be prevented. It is for the purpose 
of calling attention to some of these methods and processes, 
together with some of the ill-applied processes now in use, 
that the suggestions following have been made, with the 
