Virgil, seeing his astonishment, explains why the sun is going north instead of south as it climbs the sky. The sun is now in Aries, and therefore on the equator, as we know from several passages, but Virgil begins by saying that if it were in Gemini [a more northerly sign] and kept to its ancient path, Dante would see it travelling still further northwards in its daily course. “If Castor and Pollux [stars in Gemini] were in company with that Mirror [the sun] which carries his light up and down [_i.e._ goes north and south alternately], you would see the glowing zodiac [that part in which the sun is] revolving still closer to the Bears.” Gemini is literally nearer to the constellations of the Bears than Aries, but this is not the sense of Virgil’s statement: he means merely to indicate the north in general (see Ptolemy, p. 157). “To understand why the sun goes north,” Virgil says, “you must know that this mountain and Zion [Jerusalem] are so situated on the earth that one is precisely antipodal to the other; and so, the sun’s path being between them, when he is viewed in one direction from Jerusalem, he is viewed in the opposite direction from Purgatory. If you turn from the east to your right to see him from Jerusalem, you must turn to your left in Purgatory.” Virgil speaks of the sun’s path or the ecliptic as the path which Phaëton was not able to keep, and he describes the two antipodal places as having one and the same horizon but two entirely different hemispheres. “Certainly,” replies Dante, “I have never seen anything so clearly as I now perceive what at first puzzled me. For the middle circle of the celestial motion,[398] which is called the equator in a certain art [astronomy], and which always remains between the sun and winter, [the sun crosses it departing from us in either hemisphere at the autumnal equinox], here lies to the north of us, for the reason you have given [namely, that we are in the southern hemisphere], whilst the Hebrews [inhabitants of Jerusalem] see it towards the hot region [the south].” Observe that the expression used of the equator “che sempre riman tra il sole e il verno,”[399] distinctly suggests the reversed seasons in the southern and northern hemispheres, so that Dante has no intention, as Dr. Moore suggests, of assuming by a poetic licence that it is spring in Purgatory as well as in Italy.[400] It is autumn in the southern hemisphere, but this need not distress us: the holy Mountain knows no inclement weather,[401] and in the Garden of Eden on its summit spring flowers and autumn fruits eternally flourish together.[402] An allusion is made to a tropical summer in “la terra che perde ombra.”[403] Tropical Africa is intended, where the sun at certain times passes directly overhead, and therefore casts no shadows, as the Alexandrian astronomers had observed (see p. 117). ------------------------------------------------------------------------ [398] _Cf. Conv._ III. v. 76, 191.