File:Transactions (1871) (14596923447).jpg

Identifier: transactionsmining31amer (find matches)
Title: Transactions
Year: 1871 (1870s)
Authors: American Institute of Mining, Metallurgical, and Petroleum Engineers
Subjects: Mineral industries
Publisher: New York (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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Adies Theodolite. horizontally for centering purposes, and clamped in position.This instrument had various defects, and never became popu-lar; for which reason its construction has been discontinued. Fig. 12 represents an instrument of the theodolite class con-structed by Adie, and intended to be employed as an ordinaryspirit-level (the telescope being placed upon a pair of low Ysattached to the ends of a long metal bar, fixed to the vernier-circle), and also as an ordinary theodolite, with the telescoperaised upon a pair of higher standards, as exhibited in the fig- KIM \KK- I l\ SI \.W \ 1\<. 1N-I 111 Ml 711 uiv. At the time of its construction it wa b 7< ry useful in-Btrument for railway-work, and Baited those persons who didimi wish to purchase and carry about two leparate instruments.It had the deficiency of not being supplied with :i vertical cir- Fio. L8
Text Appearing After Image:
Everests Theodolite, with Improvements. cle or semicircle, and, consequently, never became popular asa general surveying instrument. Fig. 13 differs slightly from the original form of Col.Everests theodolite, as introduced prior to 1838. The instru-ment here shown has received considerable improvement, prin-cipally in being divided upon a sloping or conical limb, insteadvol. xxxi.—45 742 REMARKS UPON SURVEYING INSTRUMENTS. of upon a flat surface. The Indian and other engineers foundthe Hat system of division inconvenient. Trough ton \ Sinnnss centering apparatus lias also beenadded to it, so that, at present, it is considered to be the beslinstrument for use in India and other hot climates. On ac-count of its comparative lightness, as well as efficiency, it isespecially useful for filling-in the details of a secondary seriesof triangles in a trigonometrical survey. It is constructedwith three verniers to the horizontal circle, placed 120° apart.It has also means for reading double

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