CRANE. | Economy of Mining Operations. 343 
Furthermore, the difference in cost becomes more pronounced 
with greater difference in size of shafts, until, as stated above, 
the rate of advance for large may also exceed that for small 
shafts. Adding to the cost of sinking, the cost of removing 
of the excavated material and pumping, which does not vary 
much with size of shaft, the cost will run somewhat above 
$6 and $8 in the two cases. | 
When the rock is easy drilling and blasting, the above 
figures may be reduced from one-half to two-thirds, making 
the cost $3 or $4 to $4 or $5.50 per foot; while, if the rock is 
extremely difficult to work, the cost may be multiplied many 
times, even reaching the high figure, for this district, of $50 
to $75. 
Water does not interfere so much in drifting as in shaft 
sinking, but ultimately the same amount of pumping must 
be done, so that the cost is approximately the same in both 
cases. | 
Cost of Stoping. 
The operation of stoping does not differ much from that of 
drifting and shaft sinking, yet the number and length of 
holes varies considerably from that of the other operations. 
With a stope ten feet wide and from 7 to 10 feet high, usu- 
ally only four holes are placed at regular distances across the 
top, and only two or three at the base or foot. These holes 
range from 8 to 10 feet in depth, which make about 54 linear 
feet of hole (6 holes, 9 feet, average). At the ordinary rate 
of drilling this could be done in five days (54+10). If the 
work is well directed, and all favorable conditions taken ad- 
vantage of, it could probably be done in four and one-half 
days, or, with charging, etc., five days. 
The charges placed in the stoping holes are larger than 
those usually employed in drifting or shaft sinking. The 
holes are squibbed so as to hold a large charge in a small 
space. The charges weigh from five to twenty-five pounds 
per hole—ten pounds may be taken as a fair average. Sixty 
pounds of powder are then necessary to a round of holes. 
