Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 115
s guides for the vertical strokes. If the horizontal lines betraced at fixed vertical intervals, and vertical strokes be drawn between themin the line of quickest descent, they supply a sufficiently accurate representa-tion of the face of the country for ordinary purposes. It is usual to make… … Fig. 226.
Mechanical drawing
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