CRANE. | Developing Mineral Properties. 209 
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Fig. 17. Driving drifts in soft ground by the forepoling method. 
When firmer ground or soft ground with little water is 
worked, the spiles may be driyen in the same manner as 
in less firm ground, but, as the material is more difficult to 
remove, a Slightly different method is employed, namely : 
‘The spiles are driven as already explained; then next to 
them, in the roof, dirt is removed, with pick and shovel, 
the whole width of the drift, and a cap is placed under them 
and held in place by props and braces. Figure 18. If the 
ground proves too soft for this method of procedure, addi- 
tional spiles are driven above the last placed cap which tend 
to relieve the pressure upon those above. When the roof 
is thus secured, for five or six feet in advance of the face of 
the drift, a cutting is made on either side of the drift. This 
cutting extends up to the last placed cap and furnishes room 
for temporary posts to be set. All that now remains is to 
remove the unworked center of the drift, and when this is 
done the drift is trimmed to the proper size and the mud 
sill placed, or if no mud sill is used the posts are set and 
the props and braces removed, allowing the spiles to settle 
on the new set. By repeating this operation, the drift is 
advanced. Figure 17. 3 
The roof may be firm enough to hold while the advanced 
cutting is being made, yet not strong enough to hold up with- 
out timbering for a permanent driveway, or the walls of the 
drift, in fairly hard ground, may become weakened by percolat- 
ing waters, or shots fired in adjacent ground. In such cases, 
sets are placed and held in position by poles which act as 
‘«studdles,’’ or spacing timbers being placed every few inches 
