Horlogiographia optica. Dialling universall and particular: speculative and practicall. In a threefold præcognita, viz. geometricall, philosophicall, and astronomicall: and a threefold practise, viz. arithmeticall, geometricall, and instrumentall. With diverse propositions of the use and benefit of shadows, serving to prick down the signes, declination, and azimuths, on sun-dials, and diverse other benefits. Illustrated by diverse opticall conceits, taken out of Augilonius, Kercherius, Clavius, and others. Lastly, topothesia, or, a feigned description of the court of art. Full of benefit for the making of dials, use of the globes, difference of meridians, and most propositions of astronomie. Together with many usefull instruments and dials in brasse, made by Walter Hayes, at the Crosse Daggers in More Fields.

Morgan, Sylvanus, 1620-1693., Goddard, John, fl. 1645-1671, engraver.

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HOROLOGIOGRAPHIA OPTICA.

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CHAP XVII.

Shewing the finding of the Elevation of the Pole, and there∣withall a Meridian without the Declination of Sun or Starre.

THis is done by erecting a gnomon horizontal, and at 3 times of the day to give a mark at the end of the Page 118 Shadows: now it is certain, that represents the Parallel of the Sunne for that day; then take three thin sticks or the like, and lay them from the top of the gnomon, to the places where the shadows fell, and on these three so standing, lay a board to ly on all three flat, and a gno∣mon in the midle of that board points to the Pole: be∣cause every Parallel the Snn moves in, is parallel to the Equinoctial, and that is at right Angles, with the pole of the World.

Now the Meridian passeth through the most elevated place of that board or circle so laid, neither can the Sun's Declination make any sensible difference in the so small proportion of 3 or 4 houres time.

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