Elements of plane and solid free-hand geometrical drawing, with lettering; and some elements of geometrical ornamental design, including the principals of harmonic angular ratios, etc. In three parts ... for draughtsmen and artisans; and teachers and students of industrial and mechanical drawing (1878)
Warren, S. Edward (Samuel Edward), 1831-1909 · New York, J. Wiley & sons · leaf 153
on Art. 20.) The angles of 120° and 153°, adjacent to each other, give theratio 4-5-, so near f-jj- = £ that it may be called a tempered f,while the three angles of 105, 120, 135 give the ratios \% -J,and f. Assembling now the ratios found, in progression, we have— * — 4 T— o o — in which we miss… … R* 13 marily afforded by enlarging the small corner squares, untilthey are exactly embraced, as at a and c, by the sides of the 100 FREE-HAND GEOMETRICAL DRAWING. corner points. The arrangement thence suggests other lineSjwhich mav or may not be preferred to the less elaborate Fig.5, on PL XL Ex.…
Geometrical drawing · Mechanical drawing
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