[From _Conv._ IV. xxiii. and III. vi., where Dante explains the use of temporal hours, we learn that mid-tierce on the day of the equinox is an hour and a half after sunrise, or 7.30 A.M. Since the sun moves through 360 degrees divided by 24, that is 15 degrees, in an hour, and his motion is vertical in equatorial countries at the equinox, it would bring him in 1½ hours to 22½ degrees above the horizon. His greatest height above the horizon at the pole is only one degree more than this, for it is obviously equal to the greatest distance between the equator and the ecliptic, _i.e._ 23½ degrees, since at the pole the equator coincides with the horizon. This gives a good idea, therefore, of the appearance of the sun in the sky to the people at _Maria_, and is a striking illustration of the difference between the polar sun and the equatorial. For at the time mentioned, the sun has only a quarter the height which it will attain at noon, when it will pass through the zenith of the Garamantes; yet this is the highest position in which the inhabitants of _Maria_ can ever see it]. If a man stood upright in _Maria_, and kept turning his face to the sun, he would see it move to his right [as we do]. After reaching his greatest height in the sky, the sun would begin to descend again, in the same spiral way like a screw turning, for another ninety revolutions or so, until once more he was circling down on the horizon, only half his body visible. Then he would be lost to sight altogether, and would begin to be seen in _Lucia_, where he would rise and descend in just the same way as in _Maria_. But if a man faced the sun in _Lucia_, he would see it moving to his left [as one does in Australia where it goes north at noon]. [Illustration: Fig. 43. The Sun at the Equinox, seen from the poles and the equator. _Conv._ III. v. (Maria, Lucia, imaginary cities at the North and South poles).] We see, then, that these places have one day in the year which is six months long, and one night of equal length, and when it is day with one, it is night with the other. Now on the circle on the globe where the Garamantes live [the equator], the sun when in Aries goes exactly overhead, not circling horizontally like a mill-stone, but vertically like a wheel, and exactly half of this wheel is visible above the horizon. After this, the sun is seen to depart and go towards _Maria_ for about 91 days; then in about the same time it returns, and enters Libra; then it goes towards _Lucia_ for about 91 days, and in the same period returns. And this place, which circles the entire globe, always has equal day and night, on whichever side of it the sun is; and twice in the year it has a very hot summer, and twice a mild winter. The regions which are between the two imaginary cities and the mid-circle, see the sun in different ways, according to their distance from these places, but the details, our author says, he will leave to the ingenious reader,