Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 67
division on the periphery coincidingwith the angle required ; remove the protractor,and draw a line through the given point and themark. Fig. 151 is a protractor with a straight-edgerevolving on a horn centre. Where the straight-edge is intersected by the edge of the protractora vernier is… … DRAWING INSTRUMENTS. 51 large, full circular protractors printed thereon, on which the courses can bereadily marked, and thus transferred to the part of the paper required by aparallel ruler, or by triangle and ruler. These sheets are of especial use inplotting at night the days work, as, on…
Mechanical drawing
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