Introductory Astronomical Writings of the Ancients

the arctic circles become [greater]. There is an extremity, a certain land lying toward the north, in which the pole stands at the zenith. And the arctic circle assumes the position of the horizon and coincides with it during the rotation of the world, and takes on the same magnitude as the equator, so that the three circles—the arctic, the equator, and the horizon—obtain the same order and position. Again, for those dwelling toward the south, the poles become lower, and the arctic circles smaller. And there is an extremity, a certain land lying to the south of us, which is that called "under the equator," in which the poles lie beneath the horizon, and the arctic circles are entirely abolished, so that instead of five parallel circles, there are three parallels: the tropics and the equator. For because of the aforementioned reasons, one must not assume that the five parallels exist universally, but that their number is set forth in relation to our own habitation. For there are some horizons in which only three parallel circles exist. And there are habitations upon the earth, the first of which is the habitation among those for whom the summer tropic circle touches the horizon and assumes the position of the arctic circle. The second is the habitation called "under the poles." The third is the habitation of which we spoke a little before, which is designated "under the equator."

Concerning the order of the five parallel circles.

Whence the order of the five parallel circles is...