E/MJ : engineering and mining journal . Pig. 1—Sketch of locati rod, inlenqtiIKfUfedwtfhaSetscrew and brassends,graduated , these points asset being referred tvthese graduationsDetail of Wall Boltand End of Rod FIGS. 1 Tii 3 SPECIAL SCHEMES IN STRAWBERRY TUNNEL SURVEY i , ... lini points. Fig., 2. nbodenRod,carrying PlJmb-bob nBatffr n+conmd iChth—iand containing?jr-*- three Lights i Fig. 3 Light box ser of their shifting; but when placed on timberthey had to be checked constantly, and it was customaryafter taking a backsight to i hei k on one or two inter-mediate hooks b
E/MJ : engineering and mining journal . Pig. 1—Sketch of locati rod, inlenqtiIKfUfedwtfhaSetscrew and brassends,graduated , these points asset being referred tvthese graduationsDetail of Wall Boltand End of Rod FIGS. 1 Tii 3 SPECIAL SCHEMES IN STRAWBERRY TUNNEL SURVEY i , ... lini points. Fig., 2. nbodenRod,carrying PlJmb-bob nBatffr n+conmd iChth—iand containing?jr-*- three Lights i Fig. 3 Light box ser of their shifting; but when placed on timberthey had to be checked constantly, and it was customaryafter taking a backsight to i hei k on one or two inter-mediate hooks before setting the new point il i ad. After the center screw hook had been set, levels wereruu, the elevation of the of the hook determinedand a grade honk set opposite the center hook and I true grade. This latter was to assist in and placing timbei el Fo leveling, anj onrenient hook was used as a backsight, and for reasonsexplained above a sight was always taken on at least oneother hook. In using overhead necessary to use d hive ted and to sub- tract backsights ami mid foresights. The locati the cent i hts and their relation to the screw hook, and th< i eal of the tunnel, are shown in Fig. 1. The elevation of the screw hook oncedetermined, it was
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
