A Treatise on Levelling, Topography, and Higher Surveying

adjustment angular attached axis back-sight barometer bisect the target bottom bubble-tube centre CHAPTER circle clamp column compass contour-lines coördinates correction cross-hairs curvature desired height determined difference of heights direction Dumpy Level equal error eye-piece feet fore-sight formula gamboge given ground half-way back hold the rod horizontal inch length level line line of collimation line of sight lower one end main socket mark means measured mercury method miles millimetres mirror move object object-glass observed angle perpendicular plane of reference plate-screws plumb-line precisely raising or lowering reading represented right angles rod held scale screws set the instrument sextant side signal slope spherical spherical excess stakes starting-point station surface Surveying taken temperature thalwegs theodolite tion transit triangle tripod tube turn the telescope turning-points upper usually vernier vernier-plate vertica vertical angles vertical plane zenith distance الله