A short treatise of dialling shewing, the making of all sorts of sun-dials, horizontal, erect, direct, declining, inclining, reclining; vpon any flat or plaine superficies, howsoeuer placed, with ruler and compasse onely, without any arithmeticall calculation. By Edvvard Wright.

CHAP. XIII. The drawing of the line of Contingence, and of the Equinoctiall circle, and how it must be diuided. (Book 13)

NOw in all Dials that be not aequinoctiall, draw a right line, EHF. so long as you can, making right angles with the substi∣lar line, which is called the line of contin∣gence, or touchline.

2 Then describe the Equinoctiall circle GHI. after this manner: Take with your compasses the shortest distance betweene H. the intersection of the line of contingence with the substilar line, and the stilar line, and leauing one foot in that interse∣ction, with the other make a pricke B. in the sub∣stilar line, whereupon describe a circle GHI. which shall be called the equinoctiall circle.

3 If the distance of the stile from the substilar be augmented, you must draw two touch lines and two aequinoctial circles: as in 10. 12. 17. figures.

4 The halfe of the aequinoctiall circle next the

line of contingence must be deuided into 12. equal parts, beginning at H, the intersection thereof with the substilar line in all direct dials, and erect or me∣ridian polars which are commonly called East or West dials erect, as in the 3. 4. 5. 6. 13. 14. 15. figures.

5 In polars not meridian nor direct, let HK, in fig. 7. & 8. (the complement of the angle which the dial ground maketh with the plaine of the me∣ridian) be numbred and marked in the aequinoctial circle, beginning at the substilar line, and procee∣ding that way which the diall ground declineth as from H. to K. for at that marke K you must begin to diuide.

6 In decliners not polars, if the stile make a right angle with the meridian line, as in the 9. 10. 11. 12. figu. a paralel to the line of contingence, drawne by the center of the aequinoctiall, shall shew the be∣ginning of the diuision, as BK in figu. 9. 10. 11. 12.

7 But if the stile make an oblique angle with the meridian line, and the line of contingencye, cut the meridian line, as in the 16. figu. your ruler laid to that cutting at X and the center of the Equinoctial B. shal shew in the peripherie thereof, the begin∣ning of the diuision K if the distance of the stile from the substilar be not augmented.

8 But if it be augmented (as in the 17. figure) the shortest distance HX betweene H the inter∣section of the touch line, with the substilar line, and the stile not augmented AV must bee taken with the compasses, and resting one foot in that interse∣ction H, with the other make a pricke Y in the

substilar line, towards B the center of the Equino∣ctiall; by which pricke Y & Z the mutuall inter∣sectiō of the next touch line with the meridian line, let a right line YZ be drawne, for BK. and BK. pa∣ralels to it drawne out of the cenrers of both the E∣quinoctials, towards the meridian line, at their cros∣sings with the Equinoctials K & K shall shew the beginnings of their diuisions.

9 But if the touch line cut not the meridian line as in the figure 18. let a paralel thereto XY bee drawne, which may cut the meridian line in Y and take with the compasses the shortest distance ZA betwixt the intersection thereof with the sub∣stilar line and the stile not augmented; and leauing one foote in that intersection Z, with the other make a pricke B in the substilar line towards the center of the Equinoctiall; from this pricke drawe a right line BY from B to Y the intersection of the said paralel with the meridian line; for BKA pa∣ralel to this line drawne out of the center of the E∣quinoctiall B. shall shew the beginning of the diui∣sion K.