Transactions . eting of February, 1873,* and was soon published in sev-eral journals. The lamp was made by Heller & Brightly, andwas contrived for use in accurate mine-surveying to take theplace of the open mine-lamp set (if not, as too often happened,overset) on the ground, or of the mere string of a plumb-bob * Trans., I, 378. NOTES ON MINE-SI i;\ EYING [NSTR1 mini-. 103 with or without a Light or a white Burface behind it. The plum-met-lamp, aa eventually made, reeta i»y trunniona on a horizontalM compensating ring, which at points .*<» from the trunniona iahung l»v two light short chaiu
Transactions . eting of February, 1873,* and was soon published in sev-eral journals. The lamp was made by Heller & Brightly, andwas contrived for use in accurate mine-surveying to take theplace of the open mine-lamp set (if not, as too often happened,overset) on the ground, or of the mere string of a plumb-bob * Trans., I, 378. NOTES ON MINE-SI i;\ EYING [NSTR1 mini-. 103 with or without a Light or a white Burface behind it. The plum-met-lamp, aa eventually made, reeta i»y trunniona on a horizontalM compensating ring, which at points .*<» from the trunniona iahung l»v two light short chaiue from a <r the minetimber over a station, or Into a wooden plug inserted in a hole drilled in the coal or rock root. Mr. Coze found that with the plummet-lamp two persona can make a very accurate Burvej[uicklv as three can by tin- old method. j and Tapes,—Mr. So>tr: saya the chain of Ritten- 163. i-J f f .1 1H. Tunnel Section-Measuring with the Sunflower. house, which comprised 80 links or 66 feet, was quite gen-erally used in American mines. Gunters chain of 66 feetwith 100 links is about 150 years older than Rittenhouse, andit would be interesting to know whv 80 links should be usedinstead of 100. I have not discovered any reference to so sin-gular an arrangement in any of the numerous works on Ritten-house or by him. Eckley B. Coxe was also the first to introduce, with Heller &Brighthrs aid, the use of the long steel tape, or chain-tape,at first 500 feet long, afterwards up to 1000 feet, instead ofchaining. Formerly the graduation scratched on the tape, or * 1rans., xxviii., 710. 104 NOTES OH MINE-SURVEYING I NSTIUM EKTS. tnarked with rivets, would often occasion breaking; or if etchedon the tape, or marked on a thin layer of solder or tin, were notvery Legible or easy to find, and were easy to efface; the steelribbon was soft, not tempered, and was consequently liable toalterations i
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
