Introductory Astronomical Writings of the Ancients

circles traced by the sun, upon which when the sun arrives, it makes the summer solstice. In this [solstice], the day becomes the longest of all those in the year, and the night becomes the shortest. After the summer solstice, however, the sun is no longer seen progressing toward the north, but it turns toward the other parts of the world; for this reason, it is called tropical. The equinoctial circle is the largest of the five parallel circles, which is bisected by the horizon, so that a semicircle is contained above the earth, and a semicircle beneath the horizon. Upon this, when the sun arrives, it makes the equinoxes, both the vernal and the autumnal. The winter tropical circle is the southernmost of the circles traced by the sun according to the rotation performed by the world; upon this, when the sun arrives, it makes the winter solstice. In this [solstice], the night becomes the longest of all those in the year, and the day becomes the shortest. After the winter solstice, however, the sun is no longer seen progressing toward the south, but it turns toward the other parts of the world; for this reason, this one also is called tropical. The antarctic circle is equal and parallel to the arctic, and it touches the horizon at one point, and is contained entirely beneath the earth, in which the stars situated therein are for us always invisible. Of the aforementioned circles, the equinoctial is the largest, followed next by the tropical; the smallest, with respect to our habitation, are the arctic. These cir-