Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 61
Fig. 136. Fig. 137 Fig. 138. of distances the plain dividers are convenient, but for ready and close ad-justment the hair dividers (Fig. 138) are most suitable. The only differenceis that in the hair dividers one of the points is attached to the body by a
Mechanical drawing
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