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 150
e the angles at a and h with any simple ratioto each other. In the figure, this ratio is \, the angles at a and5 being respectively of 30° and 60°. So much being done, mark the points b, C, a on the edge ofa slip of paper, and then adjust the position of the slip by trial. 114 FREE-HAND GEOMETRICAL… … Then, assuming any points, as n and ^, equidistant from C forconvenience, draw n m and^ r perpendicular to A B ; and drawO n and O^, and note their intersections, n^ and j?i with a^ h^.Also note c,. Finally, at n^ c^, J9, draw perpendiculars to a^ b^,and make n^)n^ = nm; c^Oj = CO ; p^ r^=^jpr.…
Geometrical drawing · Mechanical drawing
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![An illustration from Nicolai Copernici Torinensis De reuolutionibus orbium coelestium, libri VI : Habes in hoc opere iam recens nato, & aedito, studiose lector, motus stellarum, tam fixarum, quàm erraticarum, cum ex ueteribus, tum etiam ex recentibus obseruationibus restitutos: & nouis insuper ac admirabilibus hypothesibus ornatos. Habes etiam tabulas expeditissimas, ex quibus eosdem ad quoduis tempus quàm facillime caculare poteris. Igitur eme, lege, fruere. [Line in Greek] (1543)](https://img.insideoutlibrary.com/img/200/ia-nicolaicopernici00cope-340-231.webp)
