Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 117
en these lines. The lines absolutely Slope. Proportion of Black. White. 2i° or 2f ° 1 10 5 or 6 2 9 10 or 11 3 8 15 or 18 4 7 25 or 26 5 6 35 6 5 45 7 4 60 8 3 75 9 2 100 TOPOGRAPHICAL DRAWING. established and those merely sketched in must not be confounded, and shouldbe distinguished apart either… … resenting hills, but is only to be recommended when lines have been tracedand it becomes a record of facts. Fig. 230 represents, on double the scale, the
Mechanical drawing
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