Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 170
of the upper and lower edges of the central aperturecast their shadows into the interior of the cylinder, establish the position ofthe point of intersection, c, of the two curves b c f smd ace, shadows of theseedges, which is the cast shadow of the lowest point, 0, in the curve D 0, pre-viously… … FiG. 312.
Mechanical drawing
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