114 MINma INDTJSTEY. 



progress of mining goes on from below upwards. In commencing the timber- 

 ing of a stope, as for instance, at a new station or level, commonly called the 

 "track-floor," the ground-sills are usually laid parallel with, though sometimes 

 at right angles to, the direction of the stope, or the walls enclosing the body 

 of ore, and are frequently timbers of sufficient length to serve as the sill for 

 several sets. The end of a ground-sill is so framed, projecting a few inches 

 beyond the last post, that the next adjoining sill-timber, to be laid as the stope 

 progresses, may be spliced to the one already in position, the joint being made 

 under the post, as shown at s in Fig. 2, Plate IV. The sills being laid and 

 the cross-pieces adjusted in position, the posts are raised and the cap-timbers 

 are fixed in their places, everything being fitted carefully and closely together. 

 No pins, bolts, or keys are employed in the framework. The walls of the 

 chamber are sustained by a lagging of plank, inserted between the timber 

 frame and the adjacent rock. This lagging consists of 3-inch or 4-inch plank, 

 laid next the timbers and wedged, when necessary, by spiling. In time the 

 lateral pressure of the ground holds everything firmly in place. 



After a set of timbers has thus been introduced and finally put in place, 

 a floor of 3-inch planking is laid upon it, to serve as a footing for the workmen 

 in the space above. From this comes the local term of "floor" to designate 

 any particular place or point in the mine; the stations or levels, about 100 feet 

 apart, being numbered from the surface down, first, second, third, and so forth, 

 the floors being similarly numbered upward, between the several stations or 

 track-floors. 



In working a stope thus the whole width of the workable ground in the 

 body of ore is taken down at once and the timbering supplied in its place, the 

 advancing breast of the stope being carried forward from wall to wall; in 

 bodies of ordinary width this is from 10 to 20 or 25 feet, requiring, therefore, 

 in cross-section from two to six sets of timber, like those just described. 



In commencing a stope on the level of a new station the ground-set 

 or first floor is put in, and as soon as sufl^iciently advanced in the direction 

 of the stope the next set above is placed on the first of those below. Both 

 then progress at about the same rate, the lower floor being kept sufficiently in 

 advance of the upper to furnish platform and working room for the men above. 

 As the work progresses, one set or floor is raised above the other until the 



