The artificial clock-maker. A treatise of watch and clock-work. Shewing to the meanest capacities the art of calculating numbers to all sorts of movements ... and many instruments, tables and other matters never before published in any other book / By William Derham.

  • Derham, W. (William), 1657-1735
Date:
[1759]
Catalogue details

Licence: Public Domain Mark

Credit: The artificial clock-maker. A treatise of watch and clock-work. Shewing to the meanest capacities the art of calculating numbers to all sorts of movements ... and many instruments, tables and other matters never before published in any other book / By William Derham. Source: Wellcome Collection.

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    to be out of the way of the Sights, when you look through them. On the top of thefe Arms, place a fmall Rod of Iron or Wood, to turn with a joint at D, which Rod is to bear the Plumb-Lines (E. F.) and to turn backward and for- ward, fo as to bring the Plumb-Lines to the Sights at any Time. Place this In- ftrument on a Pedeftal (G. H.) to turn round on it ftiffly. Your Inftrument being thus prepared, plant it in fome convenient Place, where you may fee the Pole-Star by Night, and the Sun by Day. When the Pole-Star is on the Meridian, look through the Sight with the bigger hole, and turn the whole Inftrument about ’till you fee op- pofite Plumb-Line interfeét the Pole-Star. Take care at the fame time, that the Plumb-Lines hang fo as to Aivekde Si the Sights. Your Inftrument, thus placed, ftandeth nicely on the Meridian, fo as to fee when either Sun, Moon, or Stars come thereon. ~ When you look by Night, ’tis neceflary that a Candle fhould fhine on the Plumb- Line, that you may {ee it. If you look at the Sun, you muft guard your Eye againit the geen wit