Transactions . station. It would be convenient to have two stout wooden benches,4 ft. in length, 14 in. in width, and 2 in. in thickness, with fourlegs each, and with strong steel short spikes in all of the of the benches may have a height of 20 in., and the other i \\ I MPROVED I ORM I NlANSIT-1 IIEOD0L1 I E. 907 Buch a height as would, with an illuminated box to be placedupon it, amount to L9| in., or other convenient height Thehigher of these benches should be placed with the inner edgeof one of the longest sides to coincide with a vertical linewhich would tall upon the center of t
Transactions . station. It would be convenient to have two stout wooden benches,4 ft. in length, 14 in. in width, and 2 in. in thickness, with fourlegs each, and with strong steel short spikes in all of the of the benches may have a height of 20 in., and the other i \\ I MPROVED I ORM I NlANSIT-1 IIEOD0L1 I E. 907 Buch a height as would, with an illuminated box to be placedupon it, amount to L9| in., or other convenient height Thehigher of these benches should be placed with the inner edgeof one of the longest sides to coincide with a vertical linewhich would tall upon the center of the metal peg, or station, inthe floor of the heading A, The lower bench is placed at /. inthe center of the heading, with one of its edges coincidingwith a vertical line from the inner wall of the -haft. It i- \ BUmed that the two places where the benches are placed are level. A point. /, is then selected in the outer, r opposite, wall and middle of the shaft, and a Btrong Bteel wedge Or nail, Pio. Plan. Setting the Instrument Over a Shaft, in Transferring an Underground Line to the Surface. with a hole in the outer end, is driven or inserted into thewall of the shaft. A flexible copper wire, the diameter ofwhich must be determined, is attached by one end to the eye-hole of the steel wTedge, and stretched over the benches andalong the heading; to the other end of the wire a sufficientlyheavy plumb-bob, with a fine point, is fastened. That part ofthe wire falling from the edge of the bench to the metal peg orstatiou is of sufficient length to cause the plumb-bob to befreely suspended, and the fine point of the bob is broughtto coincide with the fine hole sunk in the center of thepeg. The coincidence is effected by moving the copper wiretransversely along the edge of the bench. AVhen this has 908 \\ [MPROVED r<»i;,M 01 TRANSIT-THEODOLITE. been done, the direction of the wire represents the future per-manent reference base-line as indicated, at one end, by themetal statio
Size: 2132px × 1172px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
