Appleton's cyclopædia of drawing, designed as a textbook for the mechanic, architect, engineer, and surveyor (1866)
Worthen, William Ezra, 1819-1897, [from old catalog] ed, Appleton, firm, publishers, New York. (1866. D. Appleton & co.) [from old catalog] · New York, D. Appleton and company · leaf 52
thus setto any small definite measure of length with the utmost precision. Theindex or zero for reading the fraction of a turn of the screw is marked onthe point limb below B. Thus this instrument may be considered as abeam compass of small dimensions and minute accuracy. The circular protractor… … 32 DRAWING mSTEUMEKTS. wliicli carries two radial bars, e c. To the extremity of one bar is a pinion,(Z, working in a tootlied rack qnite ronnd tlie outer circumference of theprotractor. To the opposite extremity of the other bar, c, is fixed a vernier,which subdivides the primary divisions on the…
