Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 78
DRAWING INSTRUMENTS. 61 dot on each side of it, and, lastly, filling in the form of the trefoil a little belowthe point of each corner of the triangle. The square (Fig. 166), which is the next form, is developed in much thesame manner. The sides are bisected, and from a point in the centre lines are
Mechanical drawing
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