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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    then affume a Point at pleafure in the Florizontal-* ime \N AE, ataconvenient Diftance from A, as at B, and from thence draw a Line paral- lel to AM, to cut the polar Line A P in P. From P draw a Line parallel to the Aorizonral- lize W AE, as the Line PC. Take the Di- ftance A B upon the’ Horizontal-line, and fet on the Line AD from A to D, ‘and ‘through D draw a Line parallel.to A M, to come into the Ftorizontal-line at R, ‘and continue it through Dorill it cut the Line PC in S, ‘a Ruler laid from A to S, and ‘the Line A'S drawn thereby, is the Sub/tile of ‘the Dial. Then at the'Point'S erect a Perpendicular to the Line A S, as the Line ST. Set the Diftance R D from S to T, and draw the Line A T, fo hall the Triangle SAT reprefent the Stile of the Dial; for a Triangular Plate in that Form, ereéted perpendicularly upon the Subfiile AS, fhall by its upper fide A T caft a Shadow to the Hour of the Day, when the Hour-lines are drawn, which is the next Thing to ‘be done. For drawing the Hour-lines, affume a Point in the Szb/tile at pleafure, through which, aid ‘at Right Angles with the Swb/file, draw the Tan- “gent-line FF as long as you can, and fetting one Foot of ‘your Commpafies, where the T'an- gent-line cuts ‘the Szfitlar, take with the other the neareft Diftance to the Stile, or Line A T, and with the fame Extent, one Foot remaining ‘iin the Point of Interfe€tion, with the other find the Point /E in in the S#s/fiile, and with the fame Ex- “tent (one Foot'refting in AB) defcribe the Semicir- clem n; ‘this doe, lay a Ruler from A, (the ‘Center of the Semicircle) to the Point where: the “Tangent-line E F ‘cuts the Meridian AM, as at QO; begin-at O to‘divide the Semicircle into 12 Ss I equal