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Page:Popular Science Monthly Volume 24.djvu/37

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fields and destroyed a great number of Roman buildings. These two mountains of volcanic erection, formed under similar conditions, at two distinct epochs corresponding in each case with a period of repose in Vesuvius, are distinguished by their regular form, which may be compared with that of the classic volcanoes of the chain of the puys of Auvergne. Both, terminating in a vast crater, have emitted, like the volcanoes of Auvergne, only a single flow of lava, which seems to have exhausted all their energy. A long period of repose followed. During more than a century "Ischia the Joyous," as it was called, rested in perfect tranquillity. The pleasure-loving Romans made of it the most enchanting resort in the world; all their magnates had villas there.

It is to be remarked that this period of repose was correspondent with a resumption of activity on Vesuvius. The first symptom of an awakening of energy in that volcano was an earthquake, which in the year 68 occasioned considerable damage in the neighboring towns. We know well how, eleven years later, in 79, the hitherto peaceful mountain, covered at the time with rich plantations and forests nearly to its crater, revealed by a sudden explosion the terrible force that was sleeping in its depths. La Somma, reduced to powder, was projected into the air; then a column of thick smoke was seen to rise vertically from the summit of the mountain, and to spread horizontally, covering the country under its immense shadows. The sun was obscured even as far as to Rome, and it was believed that the "great night of the earth" was about to begin. When light was restored, the dismantled mountain had changed its form; the luxuriant forests that had covered it had disappeared, and so had the populous cities of Herculaneum, Pompeii, and Stabise, buried, with their inhabitants, under ashes and volcanic d├ębris. From this time, Vesuvius does not appear to have emitted any eruption of lava for several hundred years; and this period of quiet at that center seems to have been marked at Ischia by a resumption of the fires of Epomeo, which had enjoyed so long a rest that large forests had grown up to the very edge of its crater. In 1302, after the island had been shaken with a succession of earthquakes during the previous year, the lava gushed out by a new opening near the city of Ischia, and in less than four hours reached the sea, having destroyed everything in its passage as if it had been a torrent of fire. The city was terribly afflicted; large houses and numerous villas were buried, with their inhabitants. The rough surface of this lava stream has resisted all weathering, and still refuses to bear any vegetation. The new eruptive phase was of long duration, and it is remarked that while it continued Vesuvius was quiet. The alternations between the eruptive movements of lava in the two volcanic centers find a natural explanation in the facts that they are both on the same line of fracture, and a subterranean communication probably exists between them.