. Transactions. e top. plosive. The respective arrangements differ in drifts, raises, andslopes. Cartridges of about \ diam., \o long, made of nitro-glycerine packed in sawdust or cornmeal, 40 to 70 per cent being nitro-glycerine, are used. The paper wrapper is slit, cartridge thrust in drillhole, and packed lightly with a wooden rod. Holes run usually from3 to 7 feet, and explosive required is proportional. Wrapping paper if ii The Le Roi Aline. 4»7 at hand and necessary is used for tamping. Forty per cent, powder isused where rock is easily broken, stronger where it is harder. Thecombustion
. Transactions. e top. plosive. The respective arrangements differ in drifts, raises, andslopes. Cartridges of about \ diam., \o long, made of nitro-glycerine packed in sawdust or cornmeal, 40 to 70 per cent being nitro-glycerine, are used. The paper wrapper is slit, cartridge thrust in drillhole, and packed lightly with a wooden rod. Holes run usually from3 to 7 feet, and explosive required is proportional. Wrapping paper if ii The Le Roi Aline. 4»7 at hand and necessary is used for tamping. Forty per cent, powder isused where rock is easily broken, stronger where it is harder. Thecombustion cap of a six foot fuse is thrust into the centre of the lastcartridge. After all the holes have been thus charged, the fuses are cutso as to time their explosions by their lengths. This requires care andexperence. The holes must break in an order. They must, of course,always break towards space. In drifts the cut holes break first, blast-ing out a wedge ; the breast holes follow, the lifters being usually last,. Fhj. XIII. -.\ New Three Iltck Cajje. to make nn even floor and hoist the muck a-> far back as in raises are similar, the orders being, cut holes, seconds, sideholes. In the stopes there is usually space below. The rock shouldbreak 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 scatter
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