_An Explanation of the Circles of the Sphere, and of
some Astronomical Terms arising therefrom._
[Sidenote: The _Circles of the Sphere_.]
In order to determine the relative situations of places upon the Earth,
as well as the positions of the fixed Stars, and other Celestial
phænomena, the Globe of the Earth is supposed to be environed by
several imaginary circles, and these are called the _Circles of the
Sphere_. These imaginary circles are either fixed, and always obtain
the same position in the Heavens, or moveable, according to the
position of the observer.
Those circles that are fixed, owe their origin to the two-fold motion
of the Earth, and are the _Equator_, and the _Ecliptic_, with their
_Secundaries_ and _Parallels._ These fixed circles are usually
delineated upon the surface of the Globes.
The moveable circles are only the _Horizon_, its _Secundaries_ and
_Parallels_: These are represented by the wooden frame, and the brass
ring, wherein the Globe is hung, and a thin plate of brass to be
screwed in a proper place, upon the said ring, as occasion requires.