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. We have now done with all those circles that are fixed, and such as are drawn upon the Globes themselves; we next proceed to the moveable circles. III. _Of the Horizon._ [Sidenote: _Horizon._] 12. The _Horizon_ is that great circle which divides the upper, or visible Hemisphere of the world, from the lower, or invisible: This circle is distinguished into two sorts, the _Sensible_, and the _Rational_. [Sidenote: _Sensible Horizon._] The _Sensible_, or _Apparent Horizon_, is that circle which limits or determinates our prospect, whether we are at land or sea, reaching as far as we can see, or it is that circle where the Sky and the Earth, or Water, seem to meet. When we are on _Terra Firma_, this circle commonly seems rugged and irregular, occasioned by the unevenness of the ground terminating our prospect; but at sea there are no such irregularities; the semidiameter of this circle varieth according to the height of the eye of the observer; if a man of six feet high stood upon a large plain, or the surface of the sea, he could not see above three miles round. This circle determines the rising and setting of the Heavenly bodies, and distinguishes Day and Night. [Sidenote: _Rational Horizon._] The _Rational_, or true _Horizon_, is a great circle passing thro’ the center of the Earth, parallel to the sensible Horizon, being distant from it by the Earth’s semidiameter, which is about 3980 miles: This distance is nothing in comparison of the immense distance of the Sun and the fixed Stars, therefore astronomers make no distinction between these two circles, but consider the apparent Horizon, or that wherein the Sun appears to rise and set, as passing thro’ the center of the Earth. [Sidenote: _Cardinal Points of the Horizon._]