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, &c. Illustrated by four hundred engravings, and a magnetic chart (1875)
Gillespie, W. M. (William Mitchell), 1816-1868 · New York, D. Appleton · leaf 117
should then direct the rod held at B tobe moved till it too is covered by the plumb-line. The point B isthen said to be in hne between A and Z. In geometrical lan-guage, B has now been placed in the vertical plane determined bythe vertical plumb-line and the pomt Z. Any number of interme-diate… … of which shows the hill in Elevation, and the lower part in Plan), two observers, B and C, each holding a rod, may placethemselves on the ridge, in the line between the two points, aanearly as tliey can guess, and so that each can at once see the otherand the pouit beyond him. B looks to Z, and by…
Surveying
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