THE SPHERE OF PROCLUS, TRANSLATED BY THOMAS LINACRE THE BRITON.

On the Axis and Poles.

The diameter of the world, around which it revolves, is called the axis of the world. The extremities of the axis are named the poles of the world, or vertices: one of these is called the northern, the other the southern. The northern is that which always appears in our habitation; the southern, conversely, is that which is always hidden beneath our horizon. There are, however, certain places on earth in which the pole that is always visible to us is not seen at all by those who dwell there. Indeed, the one that is perpetually hidden from us becomes visible to them. Again, you will also find a place on earth where both poles have an equidistant position on the horizon.

On the circles of the sphere.

Of the circles of the sphere, some are parallel or equidistant, others are oblique, and others are drawn through the poles. The equidistant are those which have the same poles as the world. These are five in number: the Arctic, the Summer Solstice, the Equator, the Winter Solstice, and the Antarctic. The Arctic circle, therefore, is the one which is clearly the largest of all those we perpetually behold, and which touches the horizon at a single point, entirely intercepted above the earth. Whatever stars are enclosed within this circle know neither rising nor setting, but are seen to revolve around the pole throughout the whole night. Furthermore, this circle in our region, [being] larger than the former...