E/MJ : engineering and mining journal . sight, so thai only two menwere required for this work, one at the instrumen* andthe other at the foresight. When the screw hooks wereplaced in plugs in the roof, there was practically do dan- ?tunnel only whei ?ci nter hook was t ly every third day. By ban • i lights on then- respective hooks the -I a line of Bight that would give both line ai Isufficiently accurate for his purposes, at the face of the ti I (or any other poinl > at any tune. II. fixed point, it was easj for him to spot the lo< ?of the \ai - holes to be drilled. 1 Line vnd Gh ide i
E/MJ : engineering and mining journal . sight, so thai only two menwere required for this work, one at the instrumen* andthe other at the foresight. When the screw hooks wereplaced in plugs in the roof, there was practically do dan- ?tunnel only whei ?ci nter hook was t ly every third day. By ban • i lights on then- respective hooks the -I a line of Bight that would give both line ai Isufficiently accurate for his purposes, at the face of the ti I (or any other poinl > at any tune. II. fixed point, it was easj for him to spot the lo< ?of the \ai - holes to be drilled. 1 Line vnd Gh ide in Ti Permanent benchmarks (for levels) were placed at vai ipoints in the tunnel, ami the elevations <it thestruction points in the heading were checked up fronnt these benchmarks at least ? i mth (from 300 to 500 ). The elevations •! die benchmarks werecheeked up occasionally from the portal benchmark. Ain. Gurley Y-level was used for all work, ami sights werelimited to 200 ft. and kept equal. While tin- instrument. .cad\,,ing „ „ , „ ???2x2 Brass? -£/- Hates 25-lb. Kail
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
