226 University Geological Survey of Kansas. 
the condition of the face permits, the arrangement of holes 
given above will be carried in vertical lines to the top of the 
drift, which, when charged and fired in the same order in 
which they were drilled (from the center outward), break 
down the whole face. However, the more common practice 
is to break out the lower portion of the face of the drift, thus 
freeing the upper part, which can readily be brought down by 
a few charges placed across the top. 
When the face is rather high the work may be carried on 
in stages, by repeating the operation of drilling and blasting 
in horizontal lines, which, however, requires too frequent 
taking down and setting up of the drill and column, as they 
cannot be left standing while blasting is being done. 
Details of Hand Drilling. 
Probably ninety per cent. of all the drilling done under 
ground is accomplished by means of the hand drill, the ex- 
penses of a compressed-air plant being too great to warrant 
such an expenditure, especially when there is not a good face 
of ore in sight. Steam might be employed, and is, along with 
compressed air in the same machine, but is not in much 
favor, due to the condensation of the steam in the workings 
and the inconvenience caused by it to the men. The expense 
of the power drills is probably the principal objection to their 
use. This objection applies not only to their first cost, but 
also to their working expense. Power drills will, however, 
come more and more into use as the mining industry grows. 
For single hand drilling only one man is necessary, but as 
most of the drilling is done by double hand work, two men 
are required to a drill—one to strike and the other to hold 
and turn the drill. 
For convenience in handling, the drills are arranged in 
series according to length. The lengths are as follows: First 
drill or starter, 18 inches long, blade 1% inches wide ; second, 
24 inches long, blade about 143 inches wide; third, 36 inches 
long, blade about 143 wide; fourth, 48 inches long, blade 
143 inches wide; fifth, 60 inches long, blade 149 inches wide ; 
sixth, 72 inches long, blade 14 inches wide, etc. The cut- 
ting edge is nearly always straight, or I-shaped—commonly 
