Copy 2

Leybourn's Dialling improv'd. Or, the whole art perform'd, I. geometrically ... II. arithmetically ... Also, how to describe all necessary furniture for sun-dials ... With reflective dialling ... To which is now added, instrumental dialling ... and likewise mechanick dialling ... with the manner of ordering oyl and colours for painting sun-dials. Concluding with tables ... / By Henry Wilson.

  • Leybourn, William, 1626-1716.
Date:
1728
Catalogue details

Licence: Public Domain Mark

Credit: Leybourn's Dialling improv'd. Or, the whole art perform'd, I. geometrically ... II. arithmetically ... Also, how to describe all necessary furniture for sun-dials ... With reflective dialling ... To which is now added, instrumental dialling ... and likewise mechanick dialling ... with the manner of ordering oyl and colours for painting sun-dials. Concluding with tables ... / By Henry Wilson. Source: Wellcome Collection.

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    and the Line A B fo ereGed, is called the: Perpendicular. PRACT IC £. Let C D bea right Line given, and let it be required to erect a Perpendicular thereupon, from. the Point B: Open yeur Compaffes to any con- venient final] Diftance, and fetting one Foot in | the Point B, with the other, make the Plate 1. other two Marks E and F, on either Fig. 1. Side of the Point B. This done, open the Compafles to any other con-- venient Diftance greater than the former, and fet- ting one Foot in the Point E, with the other draw the obfcure Arch G G, as.near as you may gues. over the given Point B. Again, (the Compaffes. being ftill opened to the fame Diftance) fet one Foot in the Point F, and with the other Foot de- fcribe another obfcure Arch H H, croffing the for- mer inthe Point A, fo is A the Point, through. which if you draw a. right Line from ‘the given Point B, that right Line A B fo drawn, thal be perpendicular to the given Line C D, ‘and from the Point B, as. was required. BEER PRE ES eae PRR OF Bs El How spon (or near) the End of a given right Line, to erect a Perpendicular. “O effec this, there are feveral Ways, but I: | will inftance Only in two, which are familiar and eafy. The.