A treatise on surveying, comprising the theory and the practice ; (1887)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, 1840- [from old catalog] ed · New York, D. Appleton and company · leaf 467
r four timbers framed into apyramid, as in Fig. 504, with a long mastprojecting above, fulfill the first and lastconditions. The mast may be made verti-cal by directing two theodolites to it, andadjusting it so that their telescopes followit up and down, their lines of sight beingat right angles to… … PLANE SURFACES. 453 signal-staff, by a bolt passing through their ends and its middle.Fig. 505 represents the signal as framed on the ground ; Fig. 506shows it erected and ready for observation, its base being steadied Fig. 505. Fig. 506. Fig. 507.
Surveying
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