194 University Geological Survey of Kansas. 
the remaining portions on the sides. The charges put in 
vertical holes along the sides will have the lines of least re- 
sistance towards the center of the shaft. 
For larger shafts more charges may be employed, and con- 
sequently a different arrangement of the same will be neces- 
sary. The plan of removing the center and so freeing the 
remaining portion is adhered to in all cases. Several differ- 
ent arrangements of holes for shaft sinking are shown in A 
and B, figure 16. By the method described above, the shaft 
is sunk until the ore is found in paying quantities, or the 
shaft is abandoned, ore not having been found. In the lat- 
ter case it serves simply as a prospect shaft. 
Methods of Cribbing. 
There are three reasons for cribbing or lining shafts, 
namely: First, to prevent caving in, which is the principal 
reason ; second, to cover up the rough irregularities of the 
walls of the shaft; and third, to furnish a firm support for 
the ladder and any machinery, such as pumps, ventilating 
flues, etc., which it may be necessary to place in the shaft. 
The necessity of having a very strong cribbing is therefore 
apparent. 
More attention is now being paid to cribbing than for- 
merly, not only in regard to the method of putting the timbers 
together, but with regard to the quality of material used. 
This has been brought about not only by the inefficiency of 
the more crudely formed and cheaper constructions, but by 
deeper mining, which is rapidly revolutionizing not only the 
size but all appurtenances of the shaft. Formerly most of 
the cribbing used consisted of small poles cut from scrub oak, 
which abounds in the district. These poles are about two to 
two and one-half inches in diameter and are cut in lengths 
to fit the shaft. The bark is left on the poles to keep them 
from slipping. But they are generally notched to better hold 
in place. 
The arrangement of the timber of the cribbing is as fol- 
lows: When, in the course of sinking, it is thought best to 
begin to crib, the floor or bottom of the shaft next to the 
walls is leveled up and the timbers are placed two by two, 
