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beginning of the four Quarters of the Ecliptic are called Cardinal Signs, viz. Aries, Cancer, Libra, and Capricorn, becauſe the Sun enters them at the beginning of the four Quarters of the year; the four Points of the Compaſs, called Eaſt, Weſt, North, and South, are called Cardinal Points alſo; and if you bring Cancer or Capricorn to the Meridian, the Cardinal Signs will coincide with, and lay over the Cardinal Points of the Horizon. Aries and Libra are alſo called Equinoctial Points and Signs, becauſe the days and nights are then equal, as you will ſee by the Planisphere; if you take the Sun's diurnal Arc on thoſe two days that the Sun enters theſe Points, the two Meridians paſſing through theſe Points, are called Colures, and that which paſſeth through the Equinoctial Points is called the Equinoctial Colure; and that which is at right Angles to it, paſſing through the Solſtitial Points, is called the Solſtitial Colure, as you will ſee them named in the Planisphere. The use of the Prime Vertical in the Planisphere is very obvious; for when, by the diurnal rotation of the Earth, any celeſtial object comes to this circle in the eaſtern Hemiſphere, it appears due Eaſt: and if it be in the weſtern Hemisphere, it is due Weſt, and its Altitude, in both Caſes, is ſeen by inſpection; alſo, when any celeſtial object comes to the ſouthern part of the Meridian, its meridian Altitude is ſeen on the ſcale of Altitude; and when any object is riſing or ſetting, its Azimuth and Amplitude are ſeen on the Horizon, with the Point of the Compaſs on which it riſes or ſets.
