Phenomena connected with an Eruption of Vesuvius.

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In the last eruption, in the night of the 23d to the 24th of October, twenty-four hours after the falling in of the great cone of scoriæ which has been mentioned, and when the small but numerous currents of lava had already flowed off, the fiery eruption of ashes and rapilli commenced; it continued without intermission for twelve days, but was greateat in the first four days.

During this period the detonations in the interior of the volcano were so violent that the mere concussion of the air, (for no earthquake movement was perceived,) rent the ceilings of the rooms in the palace of Portici.

In the neighbouring villages of Resina, Torre del Greco, Torre del Annunziata, and Bosche Tre Case, a remarkable phenomenon was witnessed.

Throughout the whole of that part of the country the air was so filled with ashes as to cause in the middle of the day profound darkness, lasting for several hours.

Lanterns were carried in the streets, as has so often been done at Quito during the eruptions of Pichincha . The flight of the inhabitants had never been more general.

Lava currents are regarded by those who dwell near Vesuvius with less dread than an eruption of ashes—a phenomenon which had never been known to such a degree in modern times; and the obscure tradition of the manner in which the destruction of Herculaneum, Pompeii, and Stabiæ took place filled the imagination of men with appalling images.

The hot aqueous vapours which rose from the crater during the eruption, and spread themselves in the atmosphere, formed, in cooling, a dense cloud, surrounding the column of fire and ashes, which rose to a height of between nine and ten thousand feet.

So sudden a condensation of vapour, and even, as Gay- Lussac has shown, the formation of the cloud itself, augmented the electric tension.

Flashes of forked lightning, issuing from the column of ashes, darted in every direction; and the rolling thunders were distinctly heard and distinguished from the sounds which proceeded from the interior of the volcano.

In no other eruption had the play of the electric forces formed so striking a feature.

On the morning of the 26th of October a surprising rumour prevailed, to the effect that a torrent of boiling water was gushing from the crater, and pouring down the slope of the cone of ashes.

The learned and zealous observer of the volcano, Monticelli, soon discovered that this erroneous rumour had arisen from an optical illusion.

The supposed torrent of water was in reality a flow of dry ashes, which, being as loose and moveable as shifting sands, issued in large quantities from a crevice in the upper margin of the crater.

The cultivated fields had suffered much from a long-continued drought which had preceded the eruption: towards its close the “volcanic thunderstorm” which has been described produced an exceedingly violent and abundant fall of rain.

This phenomenon is associated in all climates with the close of a volcanio eruption.

As during the eruption the cone of ashes is generally enveloped in cloud, and as it is in its immediate vicinity that the rain is most violent, torrents of mud are seen to descend from it in all directions, which the terrified husbandman imagines to consist of waters which have risen from the interior of the volcano and overflowed the crater.— Humboldt’s Aspects of Nature.