Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 58
a guide to the pen in describing curves (Fig. 124). For the DRAWING INSTRUMENTS. 41 t same purpose a thin, hard-rubber ruler, with soft-rubber backing, answers well,and, as it can be readily rolled up, is extremely portable. The weights above shown are very convenient in holding the drawing-paperon… … Elliptic, parabolic, and hyperbolic (see above) curves are furnished insets, but the draughtsman can make a model out of thick cardboard or cellu-loid, with which he can draw a very uniform curve. For the drawing of ellipses, very neat trammels or compasses with ellipticguides or patterns may be…
Mechanical drawing
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