Surveying ; a manual of practical instruction in the art of plane surveying, including plotting, leveling, triangulation, line running, cross-sectioning, traversing, and other details of field work (1910)
American School of Correspondence, Phillips, Alfred Edward, 1863- [from old catalog] · Chicago, American school of correspondence · leaf 82
nsnally five or six inches long,strongly magnetized, and balanced on a pivot so that it may turnfreely and thus continue to point in the same direction howevermuch the box carrying the pivot may be turned aromid. To thisend the pivot should be of the hardest steel, ground to a veryfine point, or,… … Fig. 50. cut into a more ornamental form than the south end, or the latterend may be recognized by its carrying a coil of wire to balance thedip. Intensity of directive force and sensitiveness are the chiefrequisites in a magnetic needle, and nothing is gained by makinga needle over five inches in…
Surveying
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