Circles of Longitude.
8. All great circles passing through the Poles of the ecliptic, and consequently intersecting it at right angles, are called Circles of Longitude: So that,
Longitude of any Point in the Heavens.
Place of a Star.
9. The Longitude of any Point in the Heavens (as a Star or Planet, &c.) is an arch of the ecliptic contained between the circle of longitude passing thro’ that point, and the equinoctial point ♈. And that degree of any sign which lies under the circle of longitude, passing thro’ any Star or Planet, is called the Place of that Star or Planet.
Note, The Sun never goes out of the ecliptic, and it is not usual to say the Sun’s longitude, but we commonly express it the Sun’s Place, which is that sign, degree, minute, &c., of the ecliptic, which he at any time passes.
10. All circles conceived to be drawn parallel to the ecliptic, are called Parallels of Latitude: So that,
Latitude of a Star, &c.
11. The Latitude of any point in the Heavens, (as a fixed Star, &c.) is an arch of the circle of longitude, in passing thro’ that point, and intercepted betwixt it, and the ecliptic; or, the latitude is the distance from the ecliptic; and if the said point be to the Northward of the ecliptic, it is called North Latitude; but if it be to the Southward, is called South Latitude.
Upon the Terrestrial Globe, none of the circles of longitude are described; and upon the Celestial, they are commonly drawn thro’ the beginning of every Sign; but they are all supplied upon both Globes, by fastening a thin plate of brass over one of the Poles of the ecliptic, and so as to be moved to any degree thereof at pleasure. The parallels of latitude are also supplied by the graduations upon the said plate, as shall be shewn in a proper place.