....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.”
Fifteen hundred years afterwards, and just before the Monte Nuovo eruption, the place was visited by that painful old topographer, Leandro Alberti, the Leland of Italy. The channel made by Augustus was then gone; but the lake was still on a level with the sea, for he asserts that in storms the sea broke into it: and the water, as he expressly affirms, was salt. Now, its level is several feet above that of the sea, and the water is fresh. The upheaval must have been gradual and peaceful, for the outline of the lonely mere is as perfectly rounded now as the poet Lycophron described it;—but a portion only of that bewildering succession of changes of which this coast has been the theatre: the latest vibration of that vast commotion figured in the legendary war of the Giants. Nor is it quite so wild a conjecture as some have deemed it, that the tradition which peopled this bright coast with Cimmerians—then dwellers in the everlasting mist, on the border-land between the dead and the living—had its origin in the tales of primeval navigators, who had visited the neighbourhood during some mighty and prolonged eruption, covering sea and shore with a permanent darkness which “might be felt:” like the coast of Iceland in 1783, when for a whole summer continual eruptions arose from the sea as well as the land: when “the noxious vapours that for many months infected the air, enveloped the whole island in a dense fog which obscured the sun, and was perceptible even in England and Holland.”
Still farther westward in our panoramic view, the confusion between past and present becomes even more undecipherable. Baiæ has disappeared; a stately city of pleasure, which, to judge by its remaining foundations, rose on a hillside in terraces, something like its British counterpart Bath, but with its foot washed by the Mediterranean instead of the Avon: so has Misenum, with its naval station: and not only are these towns gone, but the land on which they stood seems so to have changed its shape, through earthquakes, marine encroachments, and the labour of men, that its very outlines are altered, until the eye rests at last on the peak of Ischia, which ends the semicircle.
Thus much by way of introduction to the more immediate point of our inquiry: the changes in the general aspect and character of the earth’s vegetable covering which have taken place in the same period of two thousand years, and in the same locality.