Dante and the early astronomers . in vain to find a suo-aestion of this kind. Yet an explanation and a source of this statementis not far to seek, and instead of proving ignorance itindicates that the author of the Qucestio knew hisAlfraganus well. The passage is evidently slightlycorrupt, but the clue to its meaning lies in the wordeccentricity. In two other places of the Qucestiothe moons eccentric orbis is alluded to,^ but if wetranslate tliis as orbit we shall be introducingmodern ideas which meant nothing to Dante or his ^ Nearest Elarth. ^ Qu. vii. 4, 6, and xxiii. 52. { THE SPHERES AND
Dante and the early astronomers . in vain to find a suo-aestion of this kind. Yet an explanation and a source of this statementis not far to seek, and instead of proving ignorance itindicates that the author of the Qucestio knew hisAlfraganus well. The passage is evidently slightlycorrupt, but the clue to its meaning lies in the wordeccentricity. In two other places of the Qucestiothe moons eccentric orbis is alluded to,^ but if wetranslate tliis as orbit we shall be introducingmodern ideas which meant nothing to Dante or his ^ Nearest Elarth. ^ Qu. vii. 4, 6, and xxiii. 52. { THE SPHERES AND THE ELEMENTS. 449 contemporaries. According to Alfraganus and Ptolemythe moons orb or sphere ^ was eccentric, but this wasnot the main cause of her varying distance from was the revolution of her epicycle round its centreC, which caused her to move continually from apogeeM to perigee P; and as the whole epicycle was mean-while revolving on the deferent round C, and thesetwo periods were not quite equal, the moon was as. Fig. 52, The moons epicycle and deferent.(The dotted line represents the southern half of the deferent). often in the perigee of her epicycle when it was southas when it was north. But besides this, the deferent,being eccentric to Earth, had also a perigee and apogee;and Alfraganus says that the perigee of the eccentric isalways in the south. Saturnus, Jupiter, atque Marseccentricorum suorum absidas summas et imas habentdeclinatas a zodiaco, illas ad boream, liasce ad austrum, ^ Orbis and sphaera are used indifferently by Alfraganus toindicate the celestial spheres: thus, in ch. xii. he says Orbes, quistellarum omnes motus complectantur, numero esse octo, and on thenext page, unamquamque harum sphccrarum octo. 450 THE SPHERES AND THE ELEMENTS. secundum eandem semper deflexus mensuram: quedad-7}iodum res in Luna ohtinet. ^ The upper and lower apsides are defined in chapterxii. as the positions of apogee and perigee respectively.^ In this quotation the wo
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