AVERNUS, a lake of Campania in Italy, near Baiae, famous among the ancients for its poisonous qualities. It is described by Strabo as situated within the Lucrine Bay, deep and darksome, surrounded with steep overhanging banks, and only accessible by the narrow passage through which you sail in. Black aged groves stretched their boughs over the watery abyss, and with impenetrable foliage excluded almost every ray of wholesome light; and mephitic vapours ascending from the hot bowels of the earth, being denied free passage to the upper atmosphere, floated along the surface in poisonous mists. These circumstances produced horrors fit for such gloomy deities; while a colony of Cimmerians, as well suited to the rites as the place itself, cut dwellings in the bosom of the surrounding hills, and officiated as priests of Tartarus. Superstition, always delighting in dark ideas, early and eagerly seized upon this noxious spot, and hither she led her trembling votaries to celebrate her dismal orgies. Here she evoked the manes of departed heroes; here she offered sacrifices to the gods of the infernal regions, and attempted to dive into the secrets of futurity. Poets enlarged upon the popular theme, and painted its awful scenery with the strongest colours of their art. Homer brings Ulysses to Avernus, as to the mouth of the infernal abodes; and, in imitation of the Grecian bard, Virgil conducts his hero to the same gloomy regions. Whoever sailed thither, first did sacrifice, and endeavoured to propitiate the infernal powers, with the assistance of some priests, who attended upon the place and directed the mystic performance. Within, a fountain of pure water broke out just over the sea, which was fancied to be a vein of the river Styx. Near this fountain was the oracle; and the hot waters, frequent in those parts, were supposed to be branches of the burning Phlegethon. The poisonous effluvia from this lake were said to be so strong that they proved fatal to birds endeavouring to fly over it. Virgil ascribes the exhalation, not to the lake itself, but to the cavern near it, which was called Avernus, or Cave of the Sybil, and through which the poets feigned a descent to Orcus. Hence the proper name of the lake is Lacus Averni, the lake near the cavern, as it is called by some ancient authors.

The sanctity of these shades remained unimpeached for many ages. Hannibal marched his army to offer incense at this altar; but it may be suspected he was led to such an act of devotion rather by the hopes of surprising the garrison of Puteoli, than by his piety. After a long reign of undisturbed gloom and celebrity, a sudden glare of light was let in upon Avernus; the horrors were dispelled, and with them vanished the sanctity of the lake. The axe of Agrippa levelled its forest with the ground, disturbed its sleepy waters with ships, and gave room for all its malignant effluvia to escape. The virulence of these exhalations, as described by ancient authors, has appeared so very extraordinary, that some modern writers, who know the place in a cleared state only, charge these accounts with exaggeration; but others think them entitled to more respect, since even now the air is feverish and dangerous, as the jaundiced faces of the vine-dressers, who have succeeded the Sybils and Cimmerians in the possession of the temple, most ruefully testify.