Introductory Astronomical Writings of the Ancients

is the same for all. But in our own inhabited world, the first is named the arctic, the second the summer tropic, then the equator, and the winter. The fifth is the antarctic. For those who dwell further toward the north than we do, the summer tropic sometimes becomes the first, the arctic the second, the equator the third, the antarctic the fourth, and the winter tropic the fifth. For where the arctic circle becomes larger than the summer tropic, it is necessary for the aforementioned order to exist.

Concerning the power of the five parallel circles.

Likewise, the powers of the five parallel circles are not the same. For the summer tropic circle among us becomes the winter tropic circle for the antipodes. And the summer tropic circle among them becomes the winter tropic for us. For those dwelling under the equator, by their power, the three circles are summer tropics, for they lie under the very passage of the sun. But in relation to their mutual variation, the equator among us would become the summer tropic, and the two tropics would be the winter ones. For by nature and universally, in relation to the entire inhabited world, the summer tropic circle may be said to be the one that is nearest to the habitation. For which reason, for those dwelling under the equator, the equator becomes the summer tropic, for then the sun comes to be directly over their heads. And all the parallels become equinoctial circles among them, for there is perpetual equinox among them.