a lake of Campania in Italy, near Baiae, famous among the ancients for its poisonous qualities. The following is the description given of it by Strabo. "Next to Baiae lies the Lucrine bay, and within it the lake Avernus. It was here that Homer had described Ulysses as conversing with Tiresias's ghost; for here they said was the oracle faced to the shades, which Ulysses came and consulted concerning his return. The Avernus is a deep darksome lake, with a narrow entry from the outer bay; it is surrounded with steep banks that hang threatening over it; and is only accessible by the narrow passage thro' which you fail in. These banks were anciently quite overgrown with a wild wood, impenetrable to the human foot. Its gloomy shade impressed an awful superstition upon the minds of the beholders; whence it was reputed the habitation of the Cimmerians who dwelt in perpetual night. Whoever failed 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; but nobody ever believed it, stating it to be a vein of the river Styx: somewhere near this fountain was the oracle; and the hot waters frequent in those parts made them think they were branches of the burning Phlegethon." The communication with the Lucrine lake is still to be distinguished, although filled up with earth; the distance between the two is but a few paces. The poisonous effluvia from this lake were said to be so strong, that they proved fatal to birds endeavouring to fly over it; but after grubbing up the wood, and building round it, no noxious effects were felt. Virgil ascribes the poisonous exhalation not to the lake itself, but to the cavern near it, which was called Avernus, or Cave of the Sibyl, and through which the poets feigned a descent to hell. Hence the proper name of the lake is Lacus Avernus, the lake near the cavern, as it is called by some ancient authors. It is now called Averno; is about two miles long, and one broad; and so far is it now from having any qualities noxious to birds, that many swim upon it. A little to the west is the cave of the sibyl; but its noxious qualities seem also to be lost. There are also some old walls standing, which some suppose to have been a temple of Apollo, and others of Pluto. Among the ancients all the places which emitted poisonous exhalations were called Avern.

AVERRHOA, in botany, a genus of the decandra order, belonging to the pentagynia class of plants. Of this genus there are three species, all natives of India, but possessing no remarkable quality.