Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 175
of the ray oflight. The shadow is simply that cast by the outer edge, A B, of the threadupon the surface of the inner cylinder; its outline is delineated in the same 158 SHADES AND SHADOWS. manner as in treating of a cylinder surmounting another of smaller diameter(Fig. 308). The shadow cast by the… … Fig. 322. and A E, as well as to those of the helix F G H and the edge H I. The shadowof the two edges J K and K L, thrown upon an inclined helical surface, ofwhich A L is the generatrix, follows the rules given in Fig. 323.
Mechanical drawing
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