Lessons in Astronomy

represents it as established; and the ends of the passing axis, upon which the revolution occurs, represent two Poles, called the one Boreal and the other Austral, upon which the entire Machine of the heavens is turned by that motion which is completed in the space of 24 hours; and as it is called "diurnal" by the Latins, so it is νυχθήμερος by the Greeks, as if "night-day," because it encompasses the space of a day and a night.

And the Sphere is not indeed woven from as many orbs as the heavens we previously described; yet the whole structure of the heavens can be understood from this simple framework of circles, insofar as, just as the former is moved upon the Spherical poles, so the latter is moved in its entirety by a single snatching away upon the poles of the World.

To be sure, although the lower heavens perform specific motions by which they withdraw themselves, as it were, toward the east—and that according to the circle which shall soon be called the Zodiac—nonetheless, they are all snatched away toward the west by a single impulse from the overarching Primum Mobile, and are carried around within the same time, namely 24 hours. Whence it also happens that the Stars established within them appear to rise and set daily, or to go and return; and the motion impressed upon them is called the Rapt motion.

Meanwhile, this Rapture supposes that all the heavens must be not only transparent, but also contiguous, solid, and hard, and that the stars adhere to them, so that they can be snatched away together. However much this may not be true in reality, it can nevertheless be admitted as a Hypothesis for explaining the motions.

As for the circles of the Sphere, they are ten in number; and of these, six are called the Major (or Greatest)