A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 266 TRIANGULAR SURVEYING. [part y (384) Signals. They must be high, conspicuous, and so madethat the instrument can be placed precisely under them. Three or four timbers framed into a Fig- 259. pyramid, as in the figure, with a long mastprojecting above, fulfil the first and lastconditions. The mast may be made verti-cal by directing two th
A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 266 TRIANGULAR SURVEYING. [part y (384) Signals. They must be high, conspicuous, and so madethat the instrument can be placed precisely under them. Three or four timbers framed into a Fig- 259. pyramid, as in the figure, with a long mastprojecting above, fulfil the first and lastconditions. The mast may be made verti-cal by directing two theodolites to it and ad-justing it so that their telescopes follow itup and down, their lines of sight being atright angles to each other. Guy ropesmay be used to keep it vertical. A very excellent signal, used on the Massachusetts State Survey,by Mr. Borden, is represented in the three following figures. It. Fig. 2C0. Fig. 261. Fig. 2fi2
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
