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 39
24 LAN3-SUR TEYIXG. needle or sharp pencil make a mark on the paper at the requirednumber of degrees, and draw a line from the mark to the givenpoint. Sometimes the protractor has an arm turning on its center and Fig. 21. … extending beyond its circumference, so that a line can be at oncedrawn by it when it is set to the desired angle. A Vernier scale issometimes added to it to increase its precision. A Rectangular Protractor is sometimes used, the divisions ofdegrees being engraved aloag three edges of a plane scale.…
Surveying
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