‘Haec super arvorum cultu pecorumque canebam ...
Illo Vergilium me tempore dulcis alebat
Parthenope, studiis florentem ignobilis oti.’
The concluding part of Book iv., originally a dirge on Cornelius Gallus, was afterwards altered for the myth of Aristaeus, to please Augustus.
Serv. ad Ecl. 10, 1, ‘Fuit Cornelius Gallus amicus Vergilii, adeo ut quartus Georgicorum a medio usque ad finem eius laudes teneret, quas postea iubente Augusto in Aristaei fabulam commutavit.’
Sources of the Georgics.—Besides his own observation, Virgil used the following authorities:
1. Hesiod—mostly in Book i., e.g. ll. 276-286 (lucky and unlucky days). Cf. ii. 176,
‘Ascraeumque cano Romana per oppida carmen.’
2. Books of the priests; e.g. i. 269 sqq. (what is lawful on holy days), i. 338 sqq. (Ambarvalia).
3. For agriculture and natural history—Greek writers like Aristotle, Theophrastus, Democritus, and Xenophon; and Latin writers like Cato and Varro.
4. Alexandrian writers for science and mythology; e.g. Eratosthenes for i. 233, ‘quinque tenent caelum zonae,’ etc.; i. 351-465, signs of weather, from the Διοσημεῖα of Aratus; iii. 425 sqq., the Calabrian serpent, from the Θηριακά of Nicander, whose writings were also used for the subject of bees in Book iv.
5. Lucretius, to whom Virgil is chiefly indebted, ii. 475 sqq., especially 490 sqq., ‘felix qui potuit,’ etc., refers to Lucretius. The idea of Lucretius, cf. v. 206-217, that man has a perpetual struggle with nature, is reflected in Virgil, but modified by his acceptance of the argument from design. Cf. i. 99,