. Transactions. eak in order downward. If breaking is freer to right or left allowanceis made. Misfires may result from defective explosive, but are moreoften the result of the premature explosion of one set of holes cuttingthe fu^e of a second set before the fire has entered the rock. Judg-27 4i; The Canadian Mining Institute. nient and care are especially necessary. This is accomplished by hav-ing a few picked men do the blasting during the night shift. At thistime few men are in the mine. The element of danger is lessened andno time is lost waiting for the smoke to clear. Contractors paid p
. Transactions. eak in order downward. If breaking is freer to right or left allowanceis made. Misfires may result from defective explosive, but are moreoften the result of the premature explosion of one set of holes cuttingthe fu^e of a second set before the fire has entered the rock. Judg-27 4i; The Canadian Mining Institute. nient and care are especially necessary. This is accomplished by hav-ing a few picked men do the blasting during the night shift. At thistime few men are in the mine. The element of danger is lessened andno time is lost waiting for the smoke to clear. Contractors paid perfoot of advance blast when ready. They are usually in a raise or cross-cut at a distance from other work. Powder supplies in the mine arekept scattered in small quantities stored in unused cross-cuts. TIMBERING. The erection of square sets is of course the main timbering posts, collar braces, and caps are exactly tenon-jointed on thesurface, and need only to be set exactly in place below. The posts of. Fig. XIV. -A New Shaft at the Black Bear Tunnel. course must be set vertical, plumb one above the other. The caps, bear-ing the tremendous lateral pressure of the hanging wall, touch end toend and form practically a continuous post between the walls. Thecollar braces running along the vein are smaller, and have only one ortwo inches of shoulder resting on the posts. All are barked, and thecaps are flattened above to receive the 3 floors. The whole mas? ofsquare sets must be set plumb from sill floor to the next level. Butt I 2 he Le Roi Mine. 419 LK ROI MINE.
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Keywords: ., book, bookcentury1800, booksubjectmineralindustries, bookyear1895
