Introductory Astronomical Writings of the Ancients

become northern. Nor is there an end until one has arrived where the pole is seen above the vertex, the northern [circle] gives way to the place of the horizon, and is joined to it in the rotation of the world, with the magnitude of the equator; and it comes to pass that three circles, the northern, the equator, and the horizon, obtain the same position and orientation. Again, however, for those who dwell toward the south, the poles become lower, and the northern circles smaller. The end of the decrease, however, is a place situated to the south for us under the equator, in which the poles are held beneath the horizon, and the northern circles have vanished entirely. Thus, out of five parallels, three finally remain, namely, with the equator, the two tropics. For one should not think that because of those things which have been said there are five parallels perpetually, but that their number exists according to our habitation: indeed, in some horizons you would find only three parallels. There are, indeed, habitations also above the earth, of which the first is that in which the solstitial circle, which touches the horizon, is held as the arctic circle itself; the second, which they call under the pole; the third, of which we reported a little before, which they name under the equator.

Wherefore neither is the order of the five parallel circles