The vertical circle passing thro’ the East and West points of the horizon, is called the _Prime Vertical_, or _Circle_ of _East_ and _West_, so that when any object is upon this circle in the Eastern hemisphere, it appears due East; and if it be in the Western hemisphere, it appears due West. [Sidenote: _Amplitude._] That degree in the horizon wherein any object rises or sets from the East or West points, is called the _Amplitude_; which for rising is called _Amplitude Ortive_, and _Occasive_ for setting; which must be also denominated whether it be Northerly or Southerly. It may be observed, that the _Amplitude_ and _Azimuth_ are much the same; the amplitude shewing the bearing of any object when he rises or sets, from the East or West points of the horizon; and the azimuth, the bearing of any object when it is above the horizon, either from the North or South point thereof. As for example, if an object rises or sets within 10 degrees of the East or West, suppose towards the South, we accordingly say, its _Amplitude_ is 10 degrees Southerly; but if an object, that is of any height above the horizon, should be in the vertical circle, passing thro’ the before-mentioned point, we then say, its _Azimuth_ is 80 degrees from the South, or 100 degrees from the North, both which expressions signify the same. [Sidenote: _Almacanthers._] [Sidenote: _Altitudes._] [Sidenote: _Meridian Altitude._] [Sidenote: _Zenith Distance._] 14. All circles drawn parallel to the horizon, in the upper hemisphere, are called _Almacanthers_, or _Parallels of Altitude_: So that the _Altitude_ of any point in the Heavens is an arch of the vertical circle passing thro’ that point, and intercepted betwixt it and the horizon; and if the object be upon the meridian, it is commonly called the _Meridian Altitude_. The complement of the altitude, or what it wants of 90 degrees, is called the _Zenith Distance_. The horizon (by which we mean the rational) is represented by the upper surface of the Wooden frame, wherein the globes are placed; upon this horizon are described several concentric circles, the innermost of which is divided into degrees, which ought to be numbered both ways from the East and the West, until they end at 90 degrees in the North and South points. The use of these divisions is to shew the amplitudes of the Sun and Stars, at their rising and setting: Also in some convenient place upon this horizon, there is commonly noted the points of the Compass. Without the before-mentioned circle there is drawn the ecliptic with its divisions, into signs, and degrees, and a circle of months and days: The use of these two circles is to serve as a kalendar to shew the Sun’s place at any time of the year, and by that means to find his place in the _Ecliptic_, drawn upon the globe itself.