CRANE. | Developing Mineral Properties. 187 
sixty feet. The breadth of the workings varies greatly, how- 
ever, due to the difference in formations found in the differ- 
ent localities. 
MINING IN SoFT GRouND.— When soft ground is worked the 
process of sinking the shafts and forming the sumps is the 
same as when hard ground is worked. ‘The shaft will, how- 
ever, always have to be lined forsupport. The drift or drifts 
are timbered by sets, consisting of sills, posts, and caps, which, 
together with sharpened stakes called ‘‘spiles’’ or ‘‘poling 
boards,’’ are driven on the sides and top of the sets. These 
I WOW MM AY 
SECTION THROUGH AB 
Fig. 12. The Varner mine, showing method of driving entries and side drifting. 
13—viii 
