Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 173
base; transfer c d to C^ d^ inplan, and project d^ to d^; its intersection with the parallel from d will beanother point in the shade, as also the point c on the central line; project F to/ on central horizontal line of elevation for another point. The lines of shadeon both sides of the ring will… … -Fig. 319. For the limit of shade on the plan, transfer C^ d^ to the opposite side of C^;Q^ d^ will be one half the minor axis and E F the major axis of an ellipse, whichwill define the line of shade for the exterior of the ring. Lay oif to g from theinterior of the ring the distance G d^; C^ g…
Mechanical drawing
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