'Georgica reverso post
Actiacam victoriam Augusto atque Atellae ... commoranti per continuum
quadriduum legit.' It was written at Naples. Cf. iv. 559,

'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 +Diosemeia+ of Aratus; iii. 425 _sqq._, the
Calabrian serpent, from the +Theriaka+ 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,

'_Exercet_que frequens tellurem atque _imperat_ arvis,'

and the whole passage i. 118-159. Lucretian science is borrowed in
passages like i. 89,

'Seu pluris calor ille vias et caeca relaxat
spiramenta, novas veniat qua sucus in herbas';

l. 415-423 (of the habits of birds); iii. 242 _sqq._ (on the passion
of love). Notice also, with Munro, Lucretian phrases like _principio_,
_quod superest_, _his animadversis_, _nunc age_, _praeterea_, _nonne
vides_, _contemplator_, _genitalia semina_.

_Political purpose of the Georgics._--The political purpose of the
Georgics is to help the policy of Augustus, which aimed at checking
the depopulation of the country districts. C