Mechanical drawing self-taught: comprising instructions in the selection and preparation of drawing instruments. Elementary instruction in practical mechanical drawing. Together with examples in simple geometry and elementary mechanism, including screw threads, gear wheels, mechanical motions, engines and boilers (1889)
in proportion as thedistance apart of the foci is diminished ; and,5 66 MECHAXICAL DRA UlXG SELF- TAUGHT. 5th. That an ellipse may be given any requiredproportion o{ width to length by locating the foci atthe requisite distance apart. The form of a true ellipse may be very nearly ap^proached by… … 78. were pencilled in by means of pins and a loop of twine,as already described, but wliich were inked in by find-ing four arcs of circles of a radius that would mostclosely approach the pencilled line ; a b are the fociof all three ellipses A, B, and C; the centre for theend curves of a are at c…
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-149-83.webp)
