Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 171
are obtained in like manner,by drawing at pleasure other lines,such as D d, parallel to A a. For the shadow cast into the in-terior of a hollow hemisphere (Fig.316), let A B C D represent thehorizontal projection of a concavehemisphere. Draw through thecentre a line, A C, perpendicular tothe ray of… … Fig. 316. ,JB^
Mechanical drawing
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