A treatise on surveying ; in which the theory and practice are fully explained (1860)
Alsop, Samuel · Philadelphia, E. C. & J. Biddle & co. · leaf 93
Chap. III. serve to hold the ring in position, asrepresented in Fig 55, and to adjustit to its proper position. The eye-piece is made to slip in and out of thetube of the telescope, so that the focusmay be brought to coincide exactlywith the intersection of cross-wires.The perfect adjustment of the… … 166. Spider-lines are generally used for making thecross-wires, though platinum wires drawn out very fineare preferable. The wire is drawn to the requisite degreeof fineness by stretching a platinum wire in the axis of acylindrical mould and casting silver around it. The com-pound wire thus formed…
Surveying
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