The San Francisco calamity by earthquake and fire Part 24

VALUE OF THE DISCOVERY OF POMPEII

This description strongly presents to us the princ.i.p.al value of the discovery of Pompeii. Interesting as are the numerous works of art found in its habitations, and important as is their bearing upon some branches of the art of the ancient world, this cannot compare in interest with the flood of light which is here thrown on ancient life in all its details, enabling us to picture to ourselves the manners and habits of life of a cultivated and flourishing population at the beginning of the Christian era, to an extent which no amount of study of ancient history could yield.

Looking upon the work of the volcano as essentially destructive, as we naturally do, we have here a valuable example of its power as a preservative agent; and it is certainly singular that it is to a volcano we owe much of what we know concerning the cities, dwellings and domestic life of the people of the Roman Empire.

It would be very fortunate for students of antiquity if similar disasters had happened to cities in other ancient civilized lands, however unfortunate it might have been to their inhabitants. But doubtless we are better off without knowledge gained from ruins thus produced.

CHAPTER XXII.

Eruptions of Vesuvius, Etna and Stromboli.

Mount Vesuvius is of especial interest as being the only active volcano on the continent of Europe--all others of that region being on the islands of the Mediterranean--and for the famous ancient eruption described in the last chapter. Before this it had borne the reputation of being extinct, but since then it has frequently shown that its fires have not burned out, and has on several occasions given a vigorous display of its powers.

During the fifteen hundred years succeeding the destructive event described eruptions were of occasional occurrence, though of no great magnitude. But throughout the long intervals when Vesuvius was at rest it was noted that Etna and Ischia were more or less disturbed.

THE BIRTH OF MONTE NUOVO

In 1538 a startling evidence was given that there was no decline of energy in the volcanic system of Southern Italy. This was the sudden birth of the mountain still known as Monte Nuovo, or New Mountain, which was thrown up in the Campania near Avernus, on the spot formerly occupied by the Lucrine Lake.

For about two years prior to this event the district had been disturbed by earthquakes, which on September 27 and 28, 1538, became almost continuous. The low sh.o.r.e was slightly elevated, so that the sea retreated, leaving bare a strip about two hundred feet in width. The surface cracked, steam escaped, and at last, early on the morning of the 29th, a greater rent was made, from which were vomited furiously "smoke, fire, stones and mud composed of ashes, making at the time of its opening a noise like the loudest thunder."

The ejected material in less than twelve hours built the hill which has lasted substantially in the same form to our day. It is a noteworthy fact that since the formation of Monte Nuovo there has been no volcanic disturbance in any part of the Neapolitan district except in Vesuvius, which for five centuries previous had remained largely at rest.

LAVA FROM VESUVIUS

The first recognised appearance of lava in the eruptions of Vesuvius was in the violent eruption of 1036. This was succeeded at intervals by five other outbreaks, none of them of great energy. After 1500 the crater became completely quiet, the whole mountain in time being grown over with luxuriant vegetation, while by the next century the interior of the crater became green with shrubbery, indicating that no injurious gases were escaping.

This was sleep, not death. In 1631 the awakening came in an eruption of terrible violence. Almost in a moment the green mantle of woodland and shrubbery was torn away and death and destruction left where peace and safety had seemed a.s.sured.

Seven streams of lava poured from the crater and swept rapidly down the mountain side, leaving ruin along their paths. Resina, Granasello and Torre del Greco, three villages that had grown up during the period of quiescence, were more or less overwhelmed by the molten lava. Great torrents of hot water also poured out, adding to the work of desolation.

It was estimated that eighteen thousand of the inhabitants were killed.

What made the horror all the greater was a frightful error of judgment, similar to that of the Governor of Martinique at St. Pierre. The Governor of Torre del Greco had refused to be warned in time, and prevented the people from making their escape until it was too late.

Not until the lava had actually reached the walls was the order for departure given. Before the order could be acted upon the molten streams burst through the walls into the crowded streets, and overwhelmed the vast majority of the inhabitants.

In this violent paroxysm the whole top of the mountain is said to have been swept away, the new crater which took the place of the old one being greatly lowered. From that date Vesuvius has never been at rest for any long interval, and eruptions of some degree of violence have been rarely more than a few years apart. Of its various later manifestations of energy we select for description that of 1767, of which an interesting account by a careful observer is extant.

GREAT ERUPTION OF 1767

From the 10th of December, 1766, to March, 1767, Vesuvius was quiet; then it began to throw up stones from time to time. In April the throws were more frequent, and at night the red glare grew stronger on the cloudy columns which hung over the crater. These repeated throws of cinders, ashes and pumice-stones so much increased the small cone of eruption which had been left in the centre of the flat crateral s.p.a.ce that its top became visible at a distance.

On the 7th of August there issued a small stream of lava from a breach in the side of a small cone; the lava gradually filled the s.p.a.ce between the cone and the crateral edge; on the 12th of September it overflowed the crater, and ran down the mountain. Stones were ejected which took ten seconds in their fall, from which it may be computed that the height which the stones reached was 1,600 feet. Padre Torre, a great observer of Vesuvius, says they went up above a thousand feet. The lava ceased on the 18th of October, but at 8 A. M. on the 19th it rushed out at a different place, after volleys of stones had been thrown to an immense height, and the huge traditional pine-tree of smoke reappeared. On this occasion that vast phantom extended its menacing shadow over Capri, at a distance of twenty-eight miles from Vesuvius.

The lava at first came out of a mouth about one hundred yards below the crater, on the side toward Monte Somma. While occupied in viewing this current, the observer heard a violent noise within the mountain; saw it split open at the distance of a quarter of a mile, and saw from the new mouth a mountain of liquid fire shoot up many feet, and then, like a torrent, roll on toward him. The earth shook; stones fell thick around him; dense clouds of ashes darkened the air; loud thunders came from the mountain top, and he took to precipitate flight. The Padre's account is too lively and instructive for his own words to be omitted.

PADRE TORRE'S NARRATIVE

"I was making my observations upon the lava, which had already, from the spot where it first broke out, reached the valley, when, on a sudden, about noon, I heard a violent noise within the mountain, and at a spot about a quarter of a mile off the place where I stood the mountain split; and with much noise, from this new mouth, a fountain of liquid fire shot up many feet high, and then like a torrent rolled on directly towards us. The earth shook at the same time that a volley of stones fell thick upon us; in an instant clouds of black smoke and ashes caused almost a total darkness; the explosions from the top of the mountain were much louder than any thunder I ever heard, and the smell of the sulphur was very offensive. My guide, alarmed, took to his heels; and I must confess that I was not at my ease. I followed close, and we ran near three miles without stopping; as the earth continued to shake under our feet, I was apprehensive of the opening of a fresh mouth which might have cut off our retreat.

"I also feared that the violent explosions would detach some of the rocks off the mountain of Somma, under which we were obliged to pa.s.s; besides, the pumice-stones, falling upon us like hail, were of such a size as to cause a disagreeable sensation in the part upon which they fell. After having taken breath, as the earth trembled greatly I thought it most prudent to leave the mountain and return to my villa, where I found my family in great alarm at the continual and violent explosions of the volcano, which shook our house to its very foundation, the doors and windows swinging upon their hinges.

"About two of the clock in the afternoon (19th) another lava stream forced its way out of the same place from whence came the lava of last year, so that the conflagration was soon as great on this side of the mountain as on the other which I had just left. I observed on my way to Naples, which was in less than two hours after I had left the mountain, that the lava had actually covered three miles of the very road through which we had retreated. This river of lava in the Atrio del Cavallo was sixty or seventy feet deep, and in some places nearly two miles broad.

Besides the explosions, which were frequent, there was a continued subterranean and violent rumbling noise, which lasted five hours in the night,--supposed to arise from contact of the lava with rain-water lodged in cavities within. The whole neighborhood was shaken violently; Portici and Naples were in the extremity of alarm; the churches were filled; the streets were thronged with processions of saints, and various ceremonies were performed to quell the fury of the mountain.

"In the night of the 20th, the occasion being critical, the prisoners in the public jail attempted to escape, and the mob set fire to the gates of the residence of the Cardinal Archbishop because he refused to bring out the relics of St. Januarius. The 21st was a quieter day, but the whole violence of the eruption returned on the 22d, at 10 A. M., with the same thundering noise, but more violent and alarming. Ashes fell in abundance in the streets of Naples, covering the housetops and balconies an inch deep. Ships at sea, twenty leagues from Naples, were covered with them.

"In the midst of these horrors, the mob, growing tumultuous and impatient, obliged the Cardinal to bring out the head of St. Januarius, at the extremity of Naples, toward Vesuvius; and it is well attested here that the eruption ceased the moment the saint came in sight of the mountain. It is true the noise ceased about that time after having lasted five hours, as it had done the preceding days.

"On the 23d the lava still ran, but on the 24th it ceased; but smoke continued. On the 25th there rose a vast column of black smoke, giving out much forked lightning with thunder, in a sky quite clear except for the smoke of the volcano. On the 26th smoke continued, but on the 27th the eruption came to an end."

This eruption was also described by Sir William Hamilton, who continued to keep a close watch on the movements of the volcano for many years.

The next outbreak of especial violence took place in 1779, when what seemed to the eye a column of fire ascended two miles high, while cinder fragments fell far and wide, destroying the hopes of harvest throughout a wide district. They fell in abundance thirty miles distant, and the dust of the explosion was carried a hundred miles away.

In 1793 the crater became active again, and in 1794 after a period of short tranquillity or comparative inaction, the mountain again became agitated, and one of the most formidable eruptions known in the history of Vesuvius began. It was in some respects unlike many others, being somewhat peculiar as to the place of its outburst, the temperature of the lava, and the course of the current. Breislak, an Italian geologist, observed the characteristic phenomena with the eye of science, and his account supplies many interesting facts.

BREISLAK ON THE ERUPTION OF 1794

Breislak remarked certain changes in the character of the earth's motions during this six hours' eruption, which led him to some particular conjecture of the cause. At the beginning the trembling was continual, and accompanied by a hollow noise, similar to that occasioned by a river falling into a subterranean cavern. The lava, at the time of its being disgorged, from the impetuous and uninterrupted manner in which it was ejected, causing it to strike violently against the walls of the vent, occasioned a continual oscillation of the mountain. Toward the middle of the night this vibratory motion ceased, and was succeeded by distant shocks. The fluid ma.s.s, diminished in quant.i.ty, now pressed less violently against the walls of the aperture, and no longer issued in a continual and gushing stream, but only at intervals, when the interior fermentation elevated the boiling matter above the mouth. About 4 A. M. the shocks began to be less numerous, and the intervals between them rendered their force and duration more perceptible.

During this tremendous eruption at the base of the Vesuvian cone, and the fearful earthquakes which accompanied it, the summit was tranquil.

The sky was serene, the stars were brilliant, and only over Vesuvius hung a thick, dark smoke-cloud, lighted up into an auroral arch by the glare of a stream of fire more than two miles long, and more than a quarter of a mile broad. The sea was calm, and reflected the red glare; while from the source of the lava came continual jets of uprushing incandescent stones. Nearer to view, Torre del Greco in flames, and clouds of black smoke, with falling houses, presented a dark and tragical foreground, heightened by the subterranean thunder of the mountain, and the groans and lamentations of fifteen thousand ruined men, women and children.

The heavy clouds of ashes which were thrown out on this occasion gathered in the early morning into a mighty shadow over Naples and the neighborhood; the sun rose pale and obscure, and a long, dim twilight reigned afterward.

Such were the phenomena on the western side of Vesuvius. They were matched by others on the eastern aspect, not visible at Naples, except by reflection of their light in the atmosphere. The lava on this side flowed eastward, along a route often traversed by lava, by the broken crest of the Cognolo and the valley of Sorienta. The extreme length to which this current reached was not less than an Italian mile. The cubic content was estimated to be half that already a.s.signed to the western currents. Taken together they amounted to 20,744,445 cubic metres, or 2,804,440 cubic fathoms; the const.i.tution of the lava being the same in each, both springing from one deep-seated reservoir of fluid rock.

The eruption of lava ceased on the 16th, and then followed heavy discharges of ashes, violent shocks of earthquakes, thunder and lightning in the columns of vapors and ashes, and finally heavy rains, lasting till the 3d of July. The barometer during all the eruption was steady.

Breislak made an approximate calculation of the quant.i.ty of ashes which fell on Vesuvius during this great eruption, and states the result as equal to what would cover a circular area 6 kilometres (about 3 1/2 English miles) in radius, and 39 centimetres (about 15 inches) in depth.

STRANGE EFFECTS