CRANE. | Economy of Mining Operations. 351 
machine has charge of it and is responsible for any and all 
damages thereto. | 
The cost of hoisting for the large mills may be summarized 
as follows (double shift) : 
HaborsGtwosmen at $2)),, per weekiich ss. en.) Gna. cele $28 00 
ODOR er eee rotenone Rtas canst sie eine Bole Tdce tegltia Galata § 2 25 
OilFandsere pairs ey weysa ces a oe es en trade Daw aes 5 00 
AICO Mest 20 EUR a0) LT at ed DO eee $35 25 
These hoisters are operated by steam which comes from 
the main boiler plant; so that the expense of the same is not 
figured into the cost of hoisting. The cost per day would 
thus be about five dollars. 
Cost of Concentrating. 
The question of concentration is an extremely important 
one, and the more variable the prevailing conditions the more 
is its importance enhanced. The high degree of hardness of 
the country rock, together with the acid waters, renders the 
problem of concentration a difficult one. 
The wear of the different apparatus, from the breaker jaws 
to the elevator bucket, is no small item of cost, the wear being 
probably more chemical than physical, due to the highly acid 
water generally prevalent throughout the district. 
The wear of the apparatus is taken up in the order in 
which ore comes to them in the process of concentration, 
which, when summed up, will be added to the other items of 
cost. The result will be about as close as it is possible to 
calculate the cost of concentration as practiced in the Galena 
district. 
WEAR OF CRUSHER JAWS. 
The range is from a few days to two weeks. This is due 
to the extreme hardness of the material crushed; also to 
the acidity of the water. The more common life of iron-jaw 
crushers is from four to eight days. Steel jaws last probably 
a third longer than iron. Iron jaws cost 10 cents per pound ; 
steel, 15 cents. The weight of iron jaws is about 40 pounds; 
of steel, from 40 to 50—making the cost of the two $4 and $6, 
respectively, or 66 cents and $1 per day. 
