Chicago : Engineering and Contracting Pub. Co. · leaf 193
ne together to a new hole. In the deeper holes, where the rock chip-pings gave trouble in making the drill stick,single bitted steel was tried in the machine,with the intention that this style bit wouldforce its way through sludge to better ad-vantage, but the men did not take to the in-novation… … Fig. 1—Plan and Elevation of Swinging Dump Track. In Unusuall\ hard ground horizontal holes car-rying water were drilled into the face of theslice, and were fired at the same time as thevertical holes. A g<id deal of the rock was broken byband drillinK before any machine drills were|.nr< haw…
Buildings
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