Crane.| Prospecting, Mining and Milling Machinery. 227 
called an I drill, while it is curved more or less, depending 
upon the character of the material to be drilled. The angle 
of the cutting edge is about sixty degrees; for the harder 
rock, about seventy degrees. The width of the blade is 
greater in the first driils of the series, or the shorter ones, so 
as to make the first part of the hole large, in order that the 
drill will not stick or bind during subsequent drilling. 
SPOON 
SAND GUN 
Fig. 24. Hand apparatus used in drilling. 
The drill is turned about one-eighth of a revolution for 
every stroke, thus keeping the hole round and preventing the 
drill from slipping and shifting to one side, thereby making 
a crooked hole. If, for any reason—as striking an extra- 
hard portion of rock, a boulder, or a crevice—the drill slips 
to one side, making a crooked or flattened hole, and so bind- 
ing the drill, the hole is generally squibbed. A small charge 
fired at the bottom of the hole will ‘‘burn’’ it out; that is, 
break up the rock for some distance around, which, when 
cleaned out, will allow the drill to proceed in a straight line 
in the direction started. Drills of greater length are used as 
the hole becomes deeper, until the desired depth is reached. 
The hole is then cleaned out thoroughly with sand pump and 
spoon (fig. 24) and squibbed. Squibbing, as referred to be- 
fore, consists in enlarging the extremity of the drill hole by 
firing a small charge of powder, placed as an ordinary shot, 
with the exception of the tamping, which should not be 
heavy enough, however, to loosen or fracture the rock mass. 
The result is a thorough breaking up of the rock within a 
radius of a few inches about the end of the hole. This 
