We have now done with all the circles of the sphere, and it may be observed, that the _Equinoctial_, the _Ecliptic_, and the _Horizon_, with their Secundaries and parallels, are all alike; and altering their position, may be made to serve for one another. Thus, if the _Poles of the World_ be brought into the _Zenith_ and _Nadir_, the _Equinoctial_ will coincide with the _Horizon_, the _Meridians_ will be the same with the _Vertical Circles_, and the parallels of _Declination_ will be the parallels of _Altitude_. After the same manner, if shifting the position, we bring the _Ecliptic_ to coincide with the _Horizon_, the circles of _Longitude_ will be the _Vertical Circles_, and the parallels of _Latitude_ and _Altitude_ will coincide. The horizon and the equator may be either parallel, perpendicular, or oblique to each other. [Sidenote: _Parallel Sphere._] 15. A _Parallel Sphere_ is that position where the equator coincides with the horizon, and consequently the poles of the world are in the Zenith and Nadir: The inhabitants of this sphere (if there be any) are those who live under the poles of the world. [Sidenote: _Right Sphere._] 16. A _Right_ or _Direct Sphere_ is that position where the equator is perpendicular to the horizon, the inhabitants whereof are those who live under the equinoctial. [Sidenote: _Oblique Sphere._] 17. An _Oblique Sphere_ is when the equinoctial and the horizon make oblique angles with each other, which every where happens but under the equator and the poles. [Sidenote: _Diurnal_ and _Nocturnal Arch_.] The arch of any parallel or declination, which stands above the horizon is called the _Diurnal Arch_; and the remaining part of it, which is below the horizon, is called the _Nocturnal Arch_. That point of the equinoctial which comes to the (Eastern/Western) part of the horizon with any point of the Heavens, is called the (Ascension/Descension) of that point, counted from the beginning of ♈; and if it be in a right sphere, the ascension or descension is called right; but if it be an oblique sphere it is called an oblique ascension or descension. So that, [Sidenote: _Right Ascension._] 18. The _Right Ascension_ of the _Sun_, _Moon_, or any _Star, &c._ is an arch of the equator contained betwixt the beginning of ♈, and that point of the equinoctial which rises with them in a _Right Sphere_, or which comes to the meridian with them in an oblique sphere. [Sidenote: _Oblique Ascension._] 19. _Oblique Ascension_, or _Descension_, is an arch of the equinoctial intercepted between the beginning of ♈, and that _Point_ of the _Equator_ which rises or sets with any point in the Heavens in an oblique sphere. [Sidenote: _Ascensional Difference._] 20. _Ascensional Difference_, is the difference betwixt the right and oblique ascension or descension, and shews how long the Sun rises or sets before or after the hour of six. IV. _Of the Division of Time._