American horological journal, devoted to practical horology (1869)
Miller, George B · New York, G. B. Miller · leaf 99
can do by suspend-ing a plumb line over the centre of the mir-ror, which line will cast a shadow on the floorat meridian, and which will be the 12 oclockhour line ; or you can construct such a lineby the process heretofore described. Thisbeing done, the meridian line on the floormust be transferred… … on the ceiling over the meridian line on thefloor. Between these two points stretch aline, charged with lamp-black and oil, andsnap it (after the manner of a chalk line), andyou have permanently the 12 oclock hourline A C ; make the angle DRP equal to thecomplement of the latitude of the place…
Clocks and watches
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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-304-198.webp)
