The Eruption of Vesuvius in 1872 Part 5

[A] For a fuller account of the literature and history of advancement of human knowledge as to Earthquakes, here merely glanced at, I must refer to my First Report on the Facts of Earthquakes, "Reports, British a.s.sociation, 1850," and to the works of Daubeny, Lyell, Phillips and others, its _complete_ history remaining yet to be written.

[B] Yet how indistinctly formed were Young's ideas, and indistinct in the same direction as those of Humboldt, becomes evident by a single sentence: "When the agitation produced by an Earthquake extends further than there is any reason to suspect a subterraneous communication, it is probably propagated through the earth nearly in the same manner as a noise is conveyed through the air."--_Lectures, Nat. Phil._, Vol. I.

[C] The Right Rev. Charles Graves, F.R.S., etc., then Fellow of Trinity College, Pres. R. I. Acad., and now Bishop of Limerick, on presentation of the Academy's Cunningham Medal.

[D] In this Report, though I have never before referred to it, and do so now with reluctance, I have always felt that the Author did me some injustice. The only reference made to my labours, published the preceding year only, is in the following words: "Many persons have regarded these phenomena (viz., Earthquakes) as due in a great measure to vibrations ... and the subject has lately been brought under our notice, in a Memoir by Mr. Mallet, 'On the Dynamics of Earthquakes,' in which he has treated it in a more determinate manner, and in more detail, than any preceding writer" (p. 74). If that Paper of mine be collated with this Report, it will be, I believe, found that, as respects the earthquake part, the latter tint parades, in a mathematical dress, some portions of the general theory of earthquake movements, previously published by me as above stated. So, also, in the chapter (p.

90) referring to Seismometry, and the important uses to Geology that might be (and since have been, to some extent) made of it, no mention is made of those instruments previously proposed by me, nor of my antic.i.p.ation of their important uses. This is but too mortifyingly suggestive of the--

"Pereant qui mea ante mihi dixerunt."

Having left this unnoticed for so many years, and during which the Author has preceded me to that bourne where our errors to each other must be forgotten, I should certainly not have now trespa.s.sed on the good rule, _De mortuis nil nisi bonum_, had I not observed very recently one amongst other results probably attributable to it. In Professor Phillips's "Vesuvius," if any one will refer to the pa.s.sage beginning "The mechanism of earthquake movement has been investigated by competent hands. The late eminent mathematician, Mr. Hopkins, explained these tremors in the solid earth by the general theory of vibratory motion,"

etc. (pages 257-259)--I think he must, in the absence of collateral information, conclude that, not I, but Mr. Hopkins, was the discoverer of the Theory of Earthquakes as explained by the general theory of vibratory motion.

Probably my friend, Professor Phillips, had not recently referred to those Memoirs and Reports of twenty-four years back, and I am thoroughly convinced that, if he has here perpetuated an injustice, he has done so unintentionally and unwittingly.

Still, the facts show how true it is that

"The ill men do lives after them, The good they do is oft interred with their bones."

And I may venture to ask my friend, should his admirable book reach, as I doubt not it will, another edition, to modify the pa.s.sage.

[E] a.s.suming the point of ejection of this block (the crater) to be 8,000 feet above where it landed, and allowing it as high a density as admissible, and the angle of projection the best for large horizontal range, it may be proved that this ma.s.s, to reach nine miles horizontally, would require an initial velocity of projection of from 1,500 to 1,600 feet per second, one as great as that of a smooth-bore cannon-shot at the muzzle, and perfectly inconceivable to be produced by a volcano.

[F] The Rev. O. Fisher, M.A., F.G.S., in a most interesting and valuable Paper, "On the Elevation of Mountain Chains by Lateral Pressure, its Cause, and the Amount of it, with a Speculation on the Origin of Volcanic Action," read, April, 1868, and published in the Transactions of the Cambridge Philosophical Society, Vol. XI., Part III., in 1869, has deduced the necessary crushing of the earth's crust by a different but closely a.n.a.logous method. I had not seen this Paper until after my own was in the hands of the Royal Society. The author's volcanic views are wholly different from my own, and do not appear to me equally valid with his notions as to elevation.--R. M.

[G] "Magna ista quia parvi sumus"--SENECA, "Quaes. Nat."

END.

TRANSLATION OF

PROFESSOR PALMIERI'S

_ACCOUNT OF_ THE ERUPTION OF VESUVIUS OF _1871-1872_

I.

ACCOUNT OF THE ERUPTION.

The great and disastrous conflagration of Vesuvius, which took place on the 26th of April, 1872, was, in my opinion, the last phase of an eruption which commenced at the end of January, 1871, an account of which I was unwilling to write, because I was convinced that it would not really terminate without a more or less violent explosion, such as I had often predicted. I shall now state the reasons upon which my prediction was founded.

When the central crater begins to heave, with slight eruptions, one may always predict a series of slight convulsions of greater or less duration, which are preparatory to the grand explosion, after which the Volcano remains for the most part in repose. Thus, when I observed the cone fissuring in November, 1868, and copious lava streams issuing from it, and flowing over the beautiful and fertile plains of the Novelle, through the Fossa della Vetrana, instead of announcing the beginning of an eruption, I announced the termination of one which had been manifest for upwards of a year by the constant flow of lava from the summit of the cone.

From the month of November, 1868, until the end of December, 1870, the mountain remained quiet, except that the fumaroles at the head of the fissure showed a degree of activity by which chlorides and sulphides of copper, sulphide of potash and other products, were engendered.

But in the beginning of 1871 the seismograph was disturbed,[1] and the crater discharged, with a slight detonation, a few incandescent projectiles. Then I announced that _a new eruption had commenced, which might be of long duration, but with phases that could not possibly be foreseen_; and on the 13th January, on the northern edge of the upper plain of the Vesuvian cone, an aperture appeared, from which at first a little lava issued, and then a small cone arose and threw out incandescent projectiles, with much smoke of a reddish colour, whilst the central crater continued to detonate more loudly and frequently. The lava-flow continued to increase until the beginning of March, without extending much beyond the base of the cone, although it had great mobility. In March, this little cone appeared not only to subside, but even partly to give way, as almost happens with eccentric cones when their activity is at an end. Upon visiting it, I observed that four prismatic or pillar-like ma.s.ses remained standing, three of which were formed of scoriae which had fallen back again in a pasty condition, and had become soldered together, the fourth consisting of a pyramidal block of compact and lithoidal lava, which appeared to have been forced up by impetus from the ground beneath. A little smoke issued from the small crater, and a loud hissing from the interior was audible. By lying along the edge, I could see a cavity of cylindrical form about ten metres in depth, tapestried with stalact.i.tic scoriae covered with sublimations of various colours. The bottom of this crater was level, but in the centre a small cone of about two metres had formed, pointed in such a manner that it possessed but a very narrow opening at the apex, from which smoke issued with a hissing sound, and from which were spurted a few very small incandescent scoriae. This little cone increased in size as well as activity until it filled the crater, and rose four or five metres above the brim.[A] New and more abundant lavas appeared near the base of this cone, and, pouring continually into the Atria del Cavallo, rushed into the Fossa della Vetrana in the direction of the Observatory and towards the Crocella, where they acc.u.mulated to such an extent as to cover the hill-side for a distance of about 300 metres; then turning below the Canteroni, they formed a hillock there without spreading much farther. These very leucitic lavas are capable of great extension, the pieces which are ejected forming for the most part very fine filiform ma.s.ses, which may be collected on the mountain in great quant.i.ties, and specimens of which I presented to the Academy under the name of _filiform lapilli_. These threads were often of a clear yellowish colour, and, when observed under the microscope, were found to consist of very minute crystals of leucite embedded in a h.o.m.ogeneous paste. The crystals were still smaller as the diameter of the threads was less, and never formed knots or swellings even in the most hair-like threads. These observations led me to reject the opinion of those who hold that crystals of leucite are pre-existent in the lava. The viscous nature of these lavas prevented their being covered with fragmentary scoriae, but caused the formation at first of a skin, which, thickening, became at last a more or less pliable sh.e.l.l, that, when more solidified, allowed the still fluid part to run as in a tube formed of this solid sh.e.l.l. For many months the lava descended thus from the cone and traversed the Atria del Cavallo, always covered, appearing below the Canteroni of a lively fluidity, until it could no longer be enveloped in its skin, which was stretched by the addition of new lava, and finally rent asunder to give room to the current until, owing to diminished liquidity, it was constrained to stop. When the lava, having traversed the covered channel it had made for itself from the top of the mountain to below the Canteroni, made its appearance still running, it frequently formed large bubbles on the surface, which mostly burst to give vent to smoke, and then disappeared.

In October, 1871, near the edge of the central crater, another small crater was formed by falling in, which, after a few days, gave vent to smoke and several jets of lava. The princ.i.p.al cone frequently opened in some point of the slope to give egress to small currents of lava, which quickly ceased. But towards the end of October the detonations increased, the smoke from the central crater issued more densely and mixed with ashes, and the seismograph and accompanying apparatus were disturbed: for all these reasons, I said in one of my bulletins, _we have either reached a new phase or the end of the eruption_, not knowing whether the new phase would be the last. On the 3rd and 4th November copious and splendid lava streams coursed down the princ.i.p.al cone on its western side, but were soon exhausted. The cone of 1871 appeared again at rest, and partly even fell in, but did not cease to emit smoke and to show fire in the interior.

In the beginning of January, 1872, the little cone again became active, the crater of the preceding October resumed strength, with frequent bellowings and projectiles, and soon after lavas of the same kind as before reappeared. The cone of 1871, formed again by the lava ejected, became so full that the lava poured from its summit in the most singular and enchanting manner. So far only an eccentric or ephemeral cone had risen close to the central crater, which, after exhaustion, regained vigour and discharged lava from the apex instead of the base, as usually happens.

In the month of February matters were somewhat moderated; but in March, with the full moon, the cone opened on the north-west side--the cleavage being manifest by a line of fumaroles--and a lava stream issued from the lowest part without any noise and with very little smoke, and poured down into the Atria del Cavallo as far as the precipices of Monte di Somma. This lava ceased flowing after a week, but the fumaroles pointed out the cleft of the cone; and between the small re-made cone, which had risen to the height of 35 metres, and the central crater, a new crater of small dimensions and interrupted activity opened.

On the 23rd April (another full moon) the Observatory instruments became agitated, the activity of the craters increased, and on the evening of the 24th splendid lavas descended the cone in various directions, attracting on the same night the visits of a great many strangers. All these lava streams were nearly exhausted on the morning of the 25th; only one remained, which issued from the base of the cone, not far from the spot whence that of the preceding month had issued. Numbers of visitors, attracted by the splendour of the lava streams of the preceding night, which they supposed still continued, soon arrived, but, finding them exhausted, were for the most part conducted by their guides to see the one still flowing. It was almost inaccessible, and to reach it one had to walk over the rough inequalities of the scoriae. It took me two hours to get there from the Observatory, when I visited it that morning, and therefore I endeavoured to dissuade those who wished to visit it at night from the attempt, but set out myself from the Observatory at 7 p.m., leaving my only a.s.sistant there. The instruments were agitated. After midnight the Observatory was closed, and my a.s.sistant retired to rest. Late and unlucky visitors pa.s.sed un.o.bserved with an escort of inexperienced guides; at half-past 3 o'clock in the morning of the 26th they were in the Atria del Cavallo, when the Vesuvian cone became rent in a north-westerly direction, the fissure commencing at the little cone which disappeared, and extending to the Atria del Cavallo, whence a copious torrent of lava issued. Two large craters formed at the summit of the mountain, discharging numerous incandescent projectiles with white ashes, and glittering with particles of mica, which frequently recurred.

A cloud of smoke enveloped these unfortunates, who were under a hail of burning projectiles and close to the lava torrent. Some were buried beneath it[B] and disappeared for ever; two dead bodies were picked up, and eleven grievously injured, one of whom died close to the Observatory. He alone revealed his name, Antonio Giannone. I learned afterwards that he was a fine young fellow, and a.s.sistant-Professor in one of the Universities.

a.s.sistant-Professors Signor Franco, who is a priest, and Signor Francesco Cozzolino, a priest also, entrusted with the festive ma.s.s for the Observatory, hastened to a.s.sist the dying. On my own return thither, the sad spectacle of the dead and dying awaited me; the former were conveyed, through the a.s.sistance of the munic.i.p.al officer of Resina, to the Cemetery, and the latter to the Hospital. But we must leave this scene of grief and sorrow, and return to the eruption.

The fissure of the cone on the north-west side was large and deep, and extended into the Atria del Cavallo, about 300 metres. No mouth opened along the cleft of the cone itself; all the lava issued from that part which extended into the Atria. From previous experience I should have expected to have seen the formation of advent.i.tious cones along the widest part of the fissure, which is never that most elevated, and these discharging from their summits aeriform matter frequently mixed with projectiles, and from their base lava; but on this occasion no cone appeared at the widest part of the fissure, but a long hillock was formed like a little chain of mountains, one point of which was elevated about fifty metres above the plain beneath, and bearing no resemblance to a cone.

Another fissure opened in the cone on the south side, which did not extend to the base, and lava issued from this and flowed in the direction of the Camaldoli. Streams of less importance furrowed the cone in other directions, but the largest quant.i.ty of lava proceeded from the fissure in the Atria del Cavallo, below the hillock or miniature chain of collines just described. This lava stream was for some time restrained within the Atria del Cavallo, among the holes and inequalities of the lavas of 1871, but these being filled up and overcome, it divided into two branches--the smaller one flowing through a hollow which separated the lavas of 1867 from those of 1871, and made its way over the lavas of 1858, threatening Resina, but stopped as soon as it reached the first cultivated ground; the larger branch precipitated itself into the Fossa della Vetrana, occupying the whole width, about 800 metres; and traversing the entire length of 1,300 metres in three hours. It dashed into the Fossa di Faraone; here it again divided into two streams, one overlying the lava of 1868, on the Plain of the Novelle, partially covering the cultivated ground and country-houses; the other flowing on through the Fossa di Faraglione, over the lava of 1855, reached the villages of Ma.s.sa and St. Sebastiano, covering a portion of the houses, and thence continued its course through the bed of a foss or trench which, contrary to my advice, had been excavated after the eruption of 1855, in the expectation of diverting the course of that lava. I did not fail to observe that the rains which previously descended through these steep channels, would in future be kept back to filtrate through the scoriae, without ever reaching the new channel.

The lava of this eruption, meeting with this said excavation, flowed into it, instead of pursuing its road over the lava of 1855, and thus invaded highly cultivated ground and towns of considerable value, extending to the very walls of a country-house belonging to the celebrated painter, Luca Giordano. This lava stream, having surmounted the obstacles which the heaps of scoriae in the Atria del Cavallo presented to it, ran with great velocity (notwithstanding its being greatly widened out in the Fossa del Vetrano), so that between 10 a.m.

and 11 p.m. it traversed about five kilometres of road, occupying a surface of five to six square kilometres. If it had not greatly slackened after midnight, from the failure of supply at its source, in twenty-four hours more, by occupying Ponticelli, it would have reached Naples, and flowed into the sea.

Although I had often visited the two villages of Ma.s.sa and St.

Sebastiano, previously greatly injured by the lava of 1855, yet I could not well estimate, upon now seeing them again, the number of houses which had disappeared. Ma.s.sa seemed to me diminished by about one-third, and St. Sebastiano by somewhat less than a fourth. But the way of escape was open to the inhabitants of Ma.s.sa; whilst a great river of lava occupying the road leading to St. Giorgio a Cremano would have hindered the flight of the inhabitants of St. Sebastiano, if they had been dilatory. The lava stream now separating the two villages is little less than a kilometre in width, and is about six metres in height.

On the night of the 26th April, the Observatory lay between two torrents of fire, which emitted an insufferable heat. The gla.s.s in the window-frames, especially on the Vetrana side, was hot and cracking, and a smell of scorching was perceptible in the rooms. The cone, besides being furrowed by the lava streams just described, was traversed by several others, which appeared and disappeared. It seemed completely perforated, and the lava oozed as it were through its whole surface. I cannot better express this phenomenon, than by saying that _Vesuvius sweated fire_. In the day-time, the cone appeared momentarily covered with white steam jets (fumaroles), which looked like flakes of cotton against the dark mountain-side, appearing and disappearing at brief intervals.

Simultaneously with the grand fissure of the cone, two large craters opened at the summit, discharging with a dreadful noise, audible at a great distance, an immense cloud of smoke and ashes with bombs and flakes, rising to the height of 1300 metres[C] above the brim of lava (_sull' orlo de essi_). The white ashes, before described, although they did not fall beyond the Crocella, were carried by the wind as far as Cosenza, from whence they were sent to me by Dr. Conti. These ejections were followed by dark sand, with lapilli and small fragments of scoriae of the same colour. The smoke, driven up with violence, a.s.sumed the usual aspect of a pine tree, of so sad a colour that it reminded us of the shadowy elm of Virgil's dreams ("_ulmus opaca ingens_"). From the trunk and branches of the pine-tree cloud fell a rain of incandescent material, which frequently covered all the cone. The lapilli and the ashes were carried to greater distances.

The victims of the morning of the 26th, the torrents of fire which threatened Resina, Bosco and Torre Annunziata, and which devastated the fertile country of the Novelle, of Ma.s.sa, St. Sebastiano and Cercola, the two partially buried villages, the continual and threatening growlings of the craters, caused such terror that numbers fled from their dwellings near the mountain into Naples, and several in Naples went to Rome or to other places. Very many delayed from the knowledge that I was in the Observatory, and held themselves in readiness for flight whenever I should abandon it.

The rapidity with which the vast torrent of fire a.s.sailed the houses (_i.e._, in these villages), and the great heat which spread to a distance, scarcely allowed the fugitives to carry away any of their belongings; many were completely dest.i.tute. The authorities vied with each other in zealous efforts to relieve the distress, and the munic.i.p.ality of Naples sheltered and fed the wretched beings for many days.

The igneous period of the eruption was short, for on the morning of the 27th the lava stream, bearing down upon Resina, having covered a few cultivated fields, stopped; the lava descending from the summit of the mountain towards the Camaldoli also stopped; and the great lava torrent, which pa.s.sed the shoulders of the Observatory through the Fossa della Vetrana, lowered the level of its surface below those of its two sides, which appeared like two parallel ramparts above it.

If these streams had continued on the 27th, flowing in the same manner as they did on the night of the 26th, they would have reached the sea, bringing destruction to the very walls of Naples.

But before leaving the subject of these lavas I must narrate an important fact to which I was witness, and which was thrice repeated, near the banks of the great river of fire that ran close to the Observatory. At three several points, and at different times, I observed great b.a.l.l.s of black smoke issue from the lava, driven up with continued violence, as if from a crater; through the smoke I frequently observed numerous projectiles thrown up into the air, but I could not say whether with noise or in silence, for the noise of the central crater was deafening. Each of these little eruptions, which I may call _external eruptions_, lasted from fifteen to twenty minutes. The first took place at the most elevated point of the Fossa della Vetrana, on the right bank of the torrent; the second, under the hill of Apicella, where the lava divided into the two branches, before described; and the third near to the Observatory on the left bank of the lava stream. These singular explosions terminated without leaving little cones or craters, the lava in its impetuosity carrying every trace away. These eruptions were seen from Naples, and the Observatory was justly believed to be in danger.

One has been clearly photographed, the one which was the best seen from Naples, being the nearest and the least darkened by the smoke of the lava. (Plate 4.) Is this the first time that the phenomenon has been remarked? I believe that it is at least the first time it has been authenticated. The authority of Julius Schmidt, quoted by Scrope, has no weight with me, for I was also a witness of what happened at Vesuvius in 1855; and, although these cones were in the midst of the lava in the Atria del Cavallo, they originated, according to the opinion of everyone, from the fissure from which the other and much larger cones proceeded. The same phenomenon was observed in the Atria del Cavallo in 1858, when I caused two of the little cones to be brought to the Observatory; but these also might belong to the fissure along which the other cones were arranged. The same may be said of the little craters observed, after they had been exhausted, by Professor Scacchi in 1850.

But the discharging mouths now observed in the Fossa della Vetrana, which existed for twenty minutes and then disappeared, and which were not at all in a continuous line, and could not be supposed to correspond with any fissure beneath, const.i.tute a circ.u.mstance which, if not new, is evident for the first time, and cause the recognition of a power in the lava itself to form eruptive fumaroles.[2]

The igneous period of the eruption having terminated on the evening of the 27th, the ashes, lapilli, and projectiles became a little more abundant, whilst the roaring noises of the craters apparently became greater. The pine-tree cloud was of a darker colour, and was furrowed by continual lightning, visible by daylight from the Observatory. Many writers on the subject of Vesuvius affirm that the flashes which appear through the smoke cloud were lightning unaccompanied with thunder, but they studied the phenomena from Naples, or some place more or less distant from the crater, where the report of the thunder was inaudible, or could not be distinguished from the bellowing and detonation of the mountain. The fact is that these flashes were constantly followed by thunder, after an interval of about seven seconds.[D] When the flash was very short, a simple noise like the report of a gun was heard, but if it were long, a protracted sound like that from torn paper ensued.

On the 28th the ashes and lapilli, continuing to fall abundantly, darkened the air, yet without diminishing the terrible noise; at Resina, Portici, St. Giorgio a Cremano, Naples, etc., terror was universal.