The Third Book of the Cross-Staff

CHAP. XIV.
To describe the Parallels of the Sines in any of the former Planes.

The Equator and the Tropicks before described do shew the Suns entrance into 4 of the Signs; the Equator into C♈ and &# 9806;, the one Tropick into ♋, and the other into &# 9809;: The rest of the intermediate Signs will be described in the same manner as the Tropicks, if first we know their Declination.

The manner of finding the Declination, not onely of the beginning of the Signs, but all other Points of the Ecliptick, is before set down in 2 Prop. Astronomical, by which you may find the declination of the beginning of ♉, ♍, and ♏, ♓ to be 11 gr. 30 m. and of ♊ ♌, ♐, and ♒ to be 20 gr. 12 m. If then you inscribe the Chords of 11 gr. 30 m. and of 20 gr. 12 m. into the former Figure BDT, pag. 64. from D toward T, the Lines drawn from B through the Terms of those Chords shall be the Signs required.

And with these declinations, the height of the Style, and the length of the Axis, you may find the Angles at the Parallel, and then the Distances between the center and the Parallel, which being pricked down upon the several Hour-lines, shall give you the Points of Intersection, by which you may draw the Parallels of the Signs, as in the Figures belonging to the Polar Planes.