absolutely no
motion.

On the inside, at two points diametrically opposite each other,
this convexity has two most sturdy poles (to speak
mechanically), projecting towards the center (which you call
the poles of the heavens), and the largest immobile semicircle,
in some manner is drawn from the center of one pole to the
center of the other. This semicircle in the middle, namely at a
point equidistant from each pole, is thought to be secured by
some sign, for example, by that "o," for arranging more
perceptibly the seat of the sun (as will be shown later). This
much must be conceived first.

You must understand that imposed on these poles is the first
mobile [Primum Mobile], everywhere convex, and divided, into 12
equal parts [Dodecatemoria], by the 6 greatest circles,
intersecting each other at the centers of the poles. Then it is
divided by another equally great circle, everywhere equidistant
from the poles, into two hemispheres. One hemisphere of 12
parts, proceeding in order from west [setting] to east [rising]
should be assigned the respective signs of the zodiac; that is,
one to Aries, the next to Taurus, and so on, etc. The circle
which cuts those 12 parts transversely in the middle, you call
the ecliptic. Then, these capital spaces of the Primum Mobile
are subdivided by degrees, minutes, etc., both in longitude and
in latitude, so that this heaven represents a kind of great
spherical net, extended to capture the longitude and latitude
of the stars, and Mobile on the aforementioned poles. Note,
however (and this is almost the leading point of the system),
in that circle of longitude which divides the sign of Gemini
from Cancer and Arcitenens [Sagittarius] from Capricorn, you
must conceive two points, directly opposite each other and
removed about twenty-three and a half degrees from the poles:
Boreal [the northern] between Gemini and Cancer; Austral [the
southern] between Sagittarius and Capricorn. These two points
by some power (imagine it is magnetic power), equal between
them, hold the terraqueous orb suspended in the middle, by
acting on the axis of the same orb (imagine it is iron) in such
a way that the earth is continually drawn to those two points
as to two opposite centers. It is never nearer to one, for as
i