Lucrine Lake, the station of Roman fleets and the very central point of Roman luxury, disappeared in the same elemental commotion; leaving a narrow stagnant pool behind. Only yon slight dyke or barrier of beach, between this shrunken mere and the sea, deserves respect; for that has remained, strange to say, almost unaltered throughout. It is one of the very oldest legendary spots of earth; doubtless the very road along which Hercules dragged the oxen of Geryon; the very “narrow shore” on which Ulysses landed, in order to call up the melancholy shades of the dead. Farther inland, again, Avernus remains unchanged, in shape at least; but many and strange are the revolutions which it has undergone in other respects. We first hear of it as a dark pool, surrounded by forests; the bed, doubtless, of an ancient crater filled with water, and retaining much of volcanic action; but not (as commonly supposed) fatal to the birds that flew over it. That notion is not classical; or rather, it is founded on a misconception of classical authorities. The pool is not called by the best writers “lacus Avernus” but “lacus Averni,” the lake _of_ the Avernus. What is an Avernus? Lucretius tells us that it is a spot where noxious gases escape from the earth, so that the birds which fly over it fall dead on the earth _or_ into the lake if there happens to be a lake below them. “Si forte lacus substratus Averno est.” And Virgil’s description, accurately construed, gives exactly the same meaning. “Spelunca alta fuit.... ....tuta lacu nigro nemorum que tenebris, _Quam_ super” (not quem super, over the cavern, not the lake) ....“haud ullæ poterant impune volantes Tendere iter pennis.... Unde _locum_” (not _lacum_) “Graii dixerunt nomine Aornon.” It was the exhalations from the mysterious cavern that were deadly, not those from the lake. Such an “Avernus” is the “Gueva Upas” or Valley of Death, in Java, to which condemned criminals were formerly sent to perish; whence the romance about the Upas Tree. And such an Avernus, on a small scale, still exists on the shore of the peaceful little Lake of Laach in Germany, also an extinct crater: there are spots on its beach where bird-corpses are to be found in numbers, killed by mephitic exhalations. But—to return to our lake—it must at that time have lain at or (like some other extinct craters) below the level of the sea; for Augustus’s great engineering operation consisted in letting the sea _into_ the lake. “Tyrrhenusque fretis immittitur æstus Avernis.”