PROCLUS' SPHERE.

On the axis and poles.

Large initial letter A at the beginning of the first paragraph.

The diameter of the world, around which it rotates, is called the axis. The extremities of the axis are called the poles of the world. Of the poles, one is called the northern, the other the southern. The northern is the one which is always visible with respect to our habitation; the southern is the one which is always invisible with respect to our horizon. There are, however, certain places on the earth where it happens that the pole which is always visible to us is invisible to them; and the pole which is invisible to us is visible to them. And again, there is a place on the earth where both poles lie equally upon the horizon.

On the circles of the sphere.

Of the circles on the sphere, some are parallel, some oblique, and others pass through the poles. Parallel are those which have the same poles as the world. There are five parallel circles: the Arctic, the summer tropical, the equinoctial, the winter tropical, and the Antarctic. The Arctic is the largest of the circles that are always visible, which touches the horizon at a single point and is taken in its entirety above the earth. In this, the stars that are situated do not undergo setting or rising, but are seen revolving around the pole throughout the whole night. This circle, in our inhabited world, is traced by the forefoot of the Great Bear. The summer tropical circle is the northernmost of the [circles] by the