Transactions . a permanent adjustment in this respect, the small nutson the upper shank of the leveling-screws were screwed downtightly against the plate. When a sight had been taken upon the flame, the lamp wasremoved, the instrument was brought forward, and the legswere clamped into the saddles, B, B, by the little set-screws at 934 THB BVOLUTIOH OF MINE-SURVEYING IXSTIUMENTS. the side. The circular base of the theodolite was also de-signed to lit perfectly into the lamp-cavity of the plate. This is another instance of the three-screw feeling competent, I shall not attemp
Transactions . a permanent adjustment in this respect, the small nutson the upper shank of the leveling-screws were screwed downtightly against the plate. When a sight had been taken upon the flame, the lamp wasremoved, the instrument was brought forward, and the legswere clamped into the saddles, B, B, by the little set-screws at 934 THB BVOLUTIOH OF MINE-SURVEYING IXSTIUMENTS. the side. The circular base of the theodolite was also de-signed to lit perfectly into the lamp-cavity of the plate. This is another instance of the three-screw feeling competent, I shall not attempt to discuss that pointfurther, bu1 will rather leave the exposition of its merits to , who I trust will favor us eventually with a more ex-tensive account of his research in England and on the conti-nent of Europe. In 1870Stanley introduced a specialform of theodolite, intendedto be universal in its appli-cation, which he termed thegeodolite; but for miningwork it was much too tall Fig. 173 Fig. Weisbachs Setzlampe. Stanleys Nadir Mining and RailroadTunnel Theodolite. and weak, so that the model was abandoned. Recently he hascome out with something novel in the way of a nadir miningtheodolite, shown in Fig. 174, which invites special attentionto the three-screw argument, as well as the shifting centerin connection with this construction. In the Stanley 4-in. model (Fig. 174), the outside diameterof the vertical axis is 2f in., the clear central aperture 2| in.,and the range of the telescope on each side of the nadir 5°.The distances between the leveling-screws mark a triangle of Tin: i:\ 0L1 MOM OF ftiINB-81 RVEYING INSTR1 KENI in. on a side, and the entire weight of the instrument aloneis L6 lbs. The horizontal ;i\i> ! this instrument is pierced topermit the diaphragm to be illuminated b\ a brackets!amp;but I regard such lamps as abominable excrescences, and theperforation of the horizontal axis as a reckless novelty, for min-ing work. The damp atmosphere
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
