With regard, again, to digressions, Racine, (le Fils) in speaking of didactic poetry, says there are two sorts of episodes which may be introduced into it, and which he terms episodes of narrative and of style, (_De Recit et de Style_,) meaning by the former the recital of the adventures of individuals, and by the latter, general reflections suggested by the subject(436). Without some embellishment of this description, most philosophic poems will correspond to Quintilian’s account of the poem of Aratus on astronomy, “Nulla varietas, nullus affectus, nulla persona, nulla cujusquam, est oratio(437).” From what has already been said concerning the extreme interest excited by the introduction of sentient beings, with all their perils around, and all their passions within them, it follows, that where the subject admits, episodes of the first class will best serve the purposes of poetry, and if the poet choose such dry and abstruse topics as cosmogony, or the generation of the world, he ought to follow the example of Silenus(438), by embellishing his subject with tales of Hylas, and Philomela, and Scylla, and the gardens of the Hesperides—the themes which induce us to listen to the lay of the poet— “Cogere donec oves stabulis, numerumque referre, Jussit, et invito processit Vesper Olympo.” It is, however, with the second class of episodes—with declamations against luxury and vice—reflections on the beauty of virtue—and the delights of rural retirement, that Lucretius hath chiefly gemmed his verses.