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"An altazimuth theodolite of an improved pattern now used on the Ordnance Survey. The horizontal circle of 14 inches diameter is read by three micrometer microscopes; the vertical circle has a diameter of 12 inches, and is read by two microscopes." — Encyclopedia Britannica, 1893

Altazimuth Theodolite

"An altazimuth theodolite of an improved pattern now used on the Ordnance Survey. The horizontal circle…

"The instrument is supported on a strong tripod, fitted with levelling screws; to this tripod is fixed the azimuth circle and a long vertical steel axis. Fitting on this axis is a hollow axis which carries on its uper end a short transverse horizontal axis. This latter carries the telescope, which, supported at the center of its length, is free to rotate in a vertical plane. The telescope is thus mounted excentrically with respect to the vertical axis around which it revolves." — Encyclopedia Britannica, 1893

Zenith Telescope

"The instrument is supported on a strong tripod, fitted with levelling screws; to this tripod is fixed…