Introductory Astronomical Writings of the Ancients

are brought to beginners, [and] are by the best right applied to the sphere. For the northern [circle] defines the stars which are perpetually visible to us. The summer tropic contains the turning of the sun, and is the limit of its transition toward the north. The equinoctial circle encompasses the equinoxes: the winter tropic is the goal of the sun’s progression toward the south, and holds within itself its winter recession. The antarctic circle determines the stars which flee our view. Therefore, since they offer certain advantages to those who are to be imbued with the first rudiments of astrology, who would doubt that they have been rightly placed upon the sphere?

On the concealment and emergence of the five equidistant [circles].

But of the five mentioned equidistant circles, the Arctic certainly exists entirely above the earth: the summer tropic, however, is cleft in two by the horizon, with the greater part of it visible above the earth, and the lesser hidden beneath. Nor yet is this circle cut by the horizon in the same way in every tract or city, but according to the variety of the climates, it receives a varying excess of the segments: also, for those who live closer to the north, it is cut more unevenly by the horizon; nor does [this] end until a place is reached where it stands entirely above the earth. But those who [dwell] more to the south