Transactions . French Miners Dial, with Telescope and Vertical Circle. telescopic M. Morin constructs also other instruments of asimilar class, mounted with two vertical arcs opposite one an-other instead of a complete vertical circle; also with a tele-scope, but without any \*ertical arc; and, again, with a longpiece of wood, pierced, for sighting-purposes, with two longi-tudinal holes. All these instruments, except Figs. 9 and 10,and the one with two vertical arcs, are mounted upon a com-mon form of ball-and-socket joint. The defects and inefficiencyof these instruments for mine-surveying ar
Transactions . French Miners Dial, with Telescope and Vertical Circle. telescopic M. Morin constructs also other instruments of asimilar class, mounted with two vertical arcs opposite one an-other instead of a complete vertical circle; also with a tele-scope, but without any \*ertical arc; and, again, with a longpiece of wood, pierced, for sighting-purposes, with two longi-tudinal holes. All these instruments, except Figs. 9 and 10,and the one with two vertical arcs, are mounted upon a com-mon form of ball-and-socket joint. The defects and inefficiencyof these instruments for mine-surveying are too apparent to re-quire any discussion. English Instruments.—Fig. 11 represents an instrument intro-duced some years since by Telford. It has only a singletanclard, upon which the vertical circle and the telescope are REMARKS DPOM SURVEYING tNSTRUM 739 jupported. It will be observed thai the single standard Israrved from the central vertical axis, which, together ivith the i . Telfords Theodolite. thickness of the vertical circle, vernier-bar and semidiameterof the telescope, permits the telescope to revolve vertically 71<) REMARKS DPON BURVBTINQ INSTRUMENTS. over the center of the instrument, like a vertical circle and the horizontal axis upon which thetelescope moves are clearly Bhown in the figure, as is also tin-mounting of the spirit-level al the back of the vertical circle,A pill-box level is inserted in a hole in the vernier horizontalcircle. In a circular box below the horizontal divided circle isplaced a traversing-plate, by means of which, and the clamp-ing plates above, the theodolite could be moved in any direction Fig. 12.
Size: 1317px × 1898px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
