Observations on Mount Vesuvius, Mount Etna, and Other Volcanos Part 3

REMARKS upon the NATURE of the SOIL of NAPLES, and its Neighbourhood.

"Mille miracula movet saciemque mutat locis, et defert montes, subrigit plana, valles extuberat novas, in profundo insulas eregit."

SENECA, De Terra-motu.

Naples, Oct. 16, 1770.

SIR,

According to your desire, I lose no time in sending you such further remarks as I have been making with some diligence, for six years past, in the compa.s.s of twenty miles, or more, round this capital. By accompanying these remarks with a map of the country I describe [Plate VI.], and with the specimens of different matters that compose the most remarkable spots of it, I do not doubt but that I shall convince you, as I am myself convinced, that the whole circuit (so far as I have examined) within the boundaries marked in the map is wholly and totally the production of subterraneous fires; and that most probably the sea formerly reached the mountains that lie behind Capua and Caserta, and are a continuation of the Appenines. If I may be allowed to compare small things with great, I imagine the subterraneous fires to have worked in this country, under the bottom of the sea, as moles in a field, throwing up here and there a hillock; and that the matter thrown out of some of these hillocks, formed into settled Volcanos, filling up the s.p.a.ce between one and the other, has composed this part of the continent, and many of the islands adjoining.

From the observations I have made upon Mount Etna, Vesuvius, and its neighbourhood, I dare say, that, after a careful examination, most mountains, that are or have been Volcanos, would be found to owe their existence to subterraneous fire; the direct reverse of what I find the commonly received opinion.

Nature, though varied, is certainly in general uniform in her operations; and I cannot conceive that two such considerable Volcanos as Etna and Vesuvius should have been formed otherwise than every other considerable Volcano of the known world. I do not wonder that so little progress has been made in the improvement of natural history, and particularly in that branch of it which regards the theory of earth; Nature acts slowly, it is difficult to catch her in the fact. Those who have made this subject their study have, without scruple, undertaken at once to write the natural history of a whole province, or of an entire continent; not reflecting, that the longest life of man scarcely affords him time to give a perfect one of the smallest insect.

I am sensible of what I undertake in giving you, Sir, even a very imperfect account of the nature of the soil of a little more than twenty miles round Naples: yet I flatter myself that my remarks, such as they are, may be of some use to any one hereafter, who may have leisure and inclination to follow them up. The kingdom of the Two Sicilies offers certainly the fairest field for observations of this kind, of any in the whole world; here are Volcanos existing in their full force, some on their decline, and others totally extinct.

To begin with some degree of order, which is really difficult in the variety of matter that occurs to my mind, I will first mention the basis on which I found all my conjectures. It is the nature of the soil that covers the antient towns of Herculaneum and Pompeii, and the interior and exterior form of the new mountain, near Puzzole, with the sort of materials of which it is composed. It cannot be denied, that Herculaneum and Pompeii stood once above ground; though now, the former is in no part less than seventy feet, and in some parts one hundred and twelve feet, below the present surface of the earth; and the latter is buried ten or twelve feet deep, more or less. As we know from the very accurate account given by Pliny the younger to Tacitus, and from the accounts of other contemporary authors, that these towns were buried by an eruption of Mount Vesuvius in the time of t.i.tus; it must be allowed, that whatever matter lies between these cities and the present surface of the earth over them, must have been produced since the year 79 of the Christian ra, the date of that formidable eruption.

Pompeii, which is situated at a much greater distance from the Volcano than Herculaneum, has felt the effects of a single eruption only; it is covered with white pumice stones, mixed with fragments of lava and burnt matter, large and small: the pumice is very light; but I have found some of the fragments of lava and cinders there, weighing eight pounds. I have often wondered, that such weighty bodies could have been carried to such a distance (for Pompeii cannot be less than five miles, in a strait line, from the mouth of Vesuvius). Every observation confirms the fall of this horrid shower over the unfortunate city of Pompeii, and that few of its inhabitants had dared to venture out of their houses; for in many of those which have been already cleared, skeletons have been found, some with gold rings, ear rings, and bracelets. I have been present at the discovery of several human skeletons myself; and under a vaulted arch, about two years ago, at Pompeii, I saw the bones of a man and a horse taken up, with the fragments of the horse's furniture, which had been ornamented with false gems set in bronze. The skulls of some of the skeletons found in the streets had been evidently fractured by the fall of the stones. His Sicilian Majesty's excavations are confined to this spot at present; and the curious in antiquity may expect hereafter, from so rich a mine, ample matter for their dissertations: but I will confine myself to such observations only as relate to my present subject.

Over the stratum of pumice and burnt matter that covers Pompeii, there is a stratum of good mould, of the thickness of about two feet and more in some parts, in which vines flourish, except in some particular spots of this vineyard, where they are subject to be blasted by a foul vapour, or _mofete_, as it is called here, that rises from beneath the burnt matter. The abovementioned shower of pumice stones, according to my observations, extended beyond Castel-a-mare (near which spot the ancient town of Stabia also lies buried under them) and covered a tract of country not less than thirty miles in circ.u.mference. It was at Stabia that Pliny the elder lost his life, and this shower of pumice stones is well described in the younger Pliny's letter. Little of the matter that has issued from Vesuvius since that time, has reached these parts: but I must observe, that the pavement of the streets of Pompeii is of lava; nay, under the foundation of the town, there is a deep stratum of lava and burnt matter. These circ.u.mstances, with many others that will be related hereafter, prove, beyond a doubt, that there have been eruptions of Vesuvius previous to that of the year 79, which is the first recorded by history.

The growth of soil by time is easily accounted for; and who, that has visited ruins of ancient edifices, has not often seen a flourishing shrub, in a good soil, upon the top of an old wall? I have remarked many such on the most considerable ruins at Rome and elsewhere. But from the soil which has grown over the barren pumice that covers Pompeii, I was enabled to make a curious observation. Upon examining the cuts and hollow ways made by currents of water in the neighbourhood of Vesuvius and of other Volcanos, I had remarked that there lay frequently a stratum of rich soil, of more or less depth, between the matter produced by the explosion of succeeding eruptions[28]; and I was naturally led to think, that such a stratum had grown in the same manner as the one abovementioned over the pumice of Pompeii. Where the stratum of good soil was thick, it was evident to me that many years had elapsed between one eruption and that which succeeded it. I do not pretend to say, that a just estimate can be formed of the great age of Volcanos from this observation; but some sort of calculation might be made: for instance, should an explosion of pumice cover again the spot under which Pompeii is buried, the stratum of rich soil abovementioned would certainly lie between two beds of pumice; and if a like accident had happened a thousand years ago, the stratum of rich soil would as certainly have wanted much of its present thickness, as the rotting of vegetables, manure, &c. is ever increasing a cultivated soil. Whenever I find then a succession of different strata of pumice and burnt matter, like that which covers Pompeii, intermixed with strata of rich soil, of greater or less depth, I hope I may be allowed reasonably to conclude, that the whole has been the production of a long series of eruptions, occasioned by subterraneous fire. By the size and weight of the pumice, and fragments of burnt erupted matter in these strata, it is easy to trace them up to their source, which I have done more than once in the neighbourhood of Puzzole, where explosions have been frequent. The gradual decrease in the size and quant.i.ty of the erupted matter in the stratum abovementioned, from Pompeii to Castle-a-Mare, is very visible: at Pompeii, as I said before, I have found them of eight pounds weight, when at Castle-a-Mare the largest do not weigh an ounce.

The matter which covers the ancient town of Herculaneum is not the produce of one eruption only; for there are evident marks that the matter of six eruptions has taken its course over that which lies immediately above the town, and was the cause of its destruction. These strata are either of lava or burnt matter, with veins of good soil between them. The stratum of erupted matter that immediately covers the town, and with which the theatre and most of the houses were filled, is not of that foul vitrified matter, called lava, but of a sort of soft stone, composed of pumice, ashes, and burnt matter. It is exactly of the same nature with what is called here the Naples stone; the Italians distinguish it by the name of _tufa_, and it is in general use for building. Its colour is usually that of our free stone, but sometimes tinged with grey, green, and yellow; and the pumice stones, with which it ever abounds, are sometimes large, and sometimes small: it varies likewise in its degree of solidity.

The chief article in the composition of _tufa_ seems to me to be, that fine burnt material, which is called _puzzolane_, whose binding quality and utility by way of cement are mentioned by Vitruvius[29], and which is to be met with only in countries that have been subject to subterraneous fires. It is, I believe, a sort of lime prepared by nature. This, mixed with water, great or small pumice stones, fragments of lava, and burnt matter, may naturally be supposed to harden into a stone of this kind[30]; and, as water frequently attends eruptions of fire, as will be seen in the accounts I shall give of the formation of the new mountain near Puzzole, I am convinced the first matter that issued from Vesuvius, and covered Herculaneum, was in the state of liquid mud. A circ.u.mstance strongly favouring my opinion is, that, about two years ago, I saw the head of an antique statue dug out of this matter within the theatre of Herculaneum; the impression of its face remains to this day in the _tufa_, and might serve as a mould for a cast in plaister of Paris, being as perfect as any mould I ever saw. As much may be inferred from the exact resemblance of this matter, or _tufa_, which immediately covers Herculaneum, to all the _tufas_ of which the high grounds of Naples and its neighbourhood are composed. I detached a piece of it sticking to, and incorporated with, the painted stucco of the inside of the theatre of Herculaneum, and shall send it for your inspection[31]. It is very different, as you will see, from the vitrified matter called lava, by which it has been generally thought that Herculaneum was destroyed. The village of Resina and some villas stand at present above this unfortunate town.

To account for the very great difference of the matters that cover Herculaneum and Pompeii, I have often thought that, in the eruption of 79, the mountain must have been open in more than one place. A pa.s.sage in Pliny's letter to Tacitus seems to say as much: "Interim Vesuvio monte pluribus locis latissim flamm, atque incendia relucebant, quorum fulgor et claritas tenebras noctis pellebat:" so that very probably the matter that covers Pompeii proceeded from a mouth, or crater, much nearer to it than is the great mouth of the Volcano, from whence came the matter that covers Herculaneum. This matter might nevertheless be said to have proceeded from Vesuvius, just as the eruption in the year 1760, which was quite independent of the great crater (being four miles from it), is properly called an eruption of Vesuvius.

In the beginning of eruptions, Volcanos frequently throw up water mixed with the ashes. Vesuvius did so in the eruption of 1631, according to the testimony of many contemporary writers. The same circ.u.mstance happened in 1669, according to the account of Ignazzio Sorrentino, who, by his history of Mount Vesuvius, printed at Naples in 1734, has shewn himself to have been a very accurate observer of the phnomena of the Volcano, for many years that he lived at Torre del Greco, situated at the foot of it. At the beginning of the formation of the new mountain, near Puzzole, water was mixed with the ashes thrown up, as will be seen in two very curious and particular accounts of the formation of that mountain, which I shall have the pleasure of communicating to you presently; and in 1755, Etna threw up a quant.i.ty of water in the beginning of an eruption, as is mentioned in the letter I sent you last year upon the subject of that magnificent Volcano[32]. Ulloa likewise mentions this circ.u.mstance of water attending the eruptions of Volcanos in America. Whenever therefore I find a _tufa_ composed exactly like that which immediately covers Herculaneum, and undoubtedly proceeded from Vesuvius, I conclude such a _tufa_ to have been produced by water mixing with the erupted matter at the time of an explosion occasioned by subterraneous fire; and this observation, I believe, will be of more use than any other, in pointing out those parts of the present _terra firma_, that have been formed by explosion. I am convinced, it has often happened that subterraneous fires and exhalations, after having been pent up and confined for some time, and been the cause of earthquakes, have forced their pa.s.sage, and in venting themselves formed mountains of the matter that confined them, as you will see was the case near Puzzole in the year 1538, and by evident signs has been so before, in many parts of the neighbourhood of Puzzole; without creating a regular Volcano. The materials of such mountains will have but little appearance of having been produced by fire, to any one unaccustomed to make observations upon the different nature of Volcanos.

If it were allowed to make a comparison between the earth and a human body, one might consider a country replete with combustibles occasioning explosions (which is surely the case here) to be like a body full of humours. When these humours concentre in one part, and form a great tumour out of which they are discharged freely, the body is less agitated; but when, by any accident, the humours are checked, and do not find free pa.s.sage through their usual channel, the body is agitated, and tumours appear in other parts of that body, but soon after the humours return again to their former channel. In a similar manner one may conceive Vesuvius to be the present great channel, through which nature discharges some of the foul humours of the earth: when these humours are checked by any accident or stoppage in this channel for any considerable time, earthquakes will be frequent in its neighbourhood, and explosions may be apprehended even at some distance from it. This was the case in the year 1538, Vesuvius having been quiet for near 400 years. There was no eruption from its great crater, from the year 1139 to the great eruption of 1631, and the top of the mountain began to lose all signs of fire. As it is not foreign to my purpose, and will serve to shew how greatly they are mistaken, who place the seat of the fire in the centre, or towards the top, of a Volcano; I will give you a curious description of the state of the crater of Vesuvius, after having been free from eruption 492 years, as related by Bracini, who descended into it not long before the eruption of 1631: "The crater was five miles in circ.u.mference, and about a thousand paces deep; its sides were covered with brush wood, and at the bottom there was a plain on which cattle grazed. In the woody parts, boars frequently harboured; in the midst of the plain, within the crater, was a narrow pa.s.sage, through which, by a winding path, you could descend about a mile amongst rocks and stones, till you came to another more s.p.a.cious plain covered with ashes: in this plain were three little pools, placed in a triangular form, one towards the East, of hot water, corrosive and bitter beyond measure; another towards the West, of water salter than that of the sea; the third of hot water, that had no particular taste."

The great increase of the cone of Vesuvius, from that time to this, naturally induces one to conclude, that the whole of the cone was raised in the like manner; and that the part of Vesuvius, called Somma, which is now considered as a distinct mountain from it, was composed in the same manner. This may plainly be perceived, by examining its interior and exterior form, and the strata of lava and burnt matter of which it is composed. The ancients, in describing Vesuvius, never mention two mountains. Strabo, Dio, Vitruvius, all agree, that Vesuvius, in their time, shewed signs of having formerly erupted[33], and the first compares the crater on its top to an amphitheatre. The mountain now called Somma was, I believe, that which the ancients called Vesuvius: its outside form is conical; its inside, instead of an amphitheatre, is now like a great theatre. I suppose the eruption in Pliny's time to have thrown down that part of the cone next the sea, which would naturally have left it in its present state; and that the conical mountain, or existing Vesuvius, has been raised by the succeeding eruptions: all my observations confirm this opinion. I have seen antient lavas in the plain on the other side of Somma, which could never have proceeded from the present Vesuvius. Serao, a celebrated physician now living at Naples, in the introduction of his account of the eruption of Vesuvius in 1737 (in which account many of the phnomena of the Volcano are recorded and very well accounted for), says, that at the convent of Dominican Fryars, called the Madona del Arco, some years ago, in sinking a well, at a hundred feet depth, a lava was discovered, and soon after another; so that, in less than three hundred feet depth, the lavas of four eruptions were found. From the situation of this convent, it is clear beyond a doubt, that these lavas proceeded from the mountain called Somma, as they are quite out of the reach of the existing Volcano.

From these circ.u.mstances, and from repeated observations I have made in the neighbourhood of Vesuvius, I am sure that no virgin soil is to be found there, and that all is composed of different strata of erupted matter, even to a great depth below the level of the sea. In short, I have not any doubt in my own mind, but that this Volcano took its rise from the bottom of the sea; and as the whole plain between Vesuvius and the mountains behind Caserta, which is the best part of the Campagna Felice, is (under its good soil) composed of burnt matter, I imagine the sea to have washed the feet of those mountains, until the subterraneous fires began to operate, at a period certainly of a most remote antiquity.

The soil of the Campagna Felice is very fertile; I saw the earth opened in many places last year in the midst of that plain, when they were seeking for materials to mend the road from Naples to Caserta. The stratum of good soil was in general four or five feet thick; under which was a deep stratum of cinders, pumice, fragments of lava, and such burnt matter as abounds near Vesuvius and all Volcanos. The mountains at the back of Caserta are mostly of a sort of lime-stone, and very different from those formed by fire; though Signior Van Vitelli, the celebrated architect, has a.s.sured me, that, in the cutting of the famous aqueduct of Caserta through these mountains, he met with some soils, that had been evidently formed by subterraneous fire. The high grounds, which extend from Castel-a-Mare, to the point of Minerva towards the island of Caprea, and from the promontory that divides the bay of Naples from that of Salerno, are of lime-stone. The plain of Sorrento, that is bounded by these high grounds, beginning at the village of Vico, and ending at that of Ma.s.sa, is wholly composed of the same sort of _tufa_ as that about Naples, except that the cinders or pumice stones intermixed in it are larger than in the Naples _tufa_. I conceive then that there has been an explosion in this spot from the bottom of the sea. This plain, as I have remarked to be the case with all soils produced by subterraneous fire, is extremely fertile; whilst the ground about it, being of another nature, is not so. The island of Caprea does not shew any signs of having been formed by subterraneous fire; but is of the same nature as the high grounds last mentioned, from which it has been probably detached by earthquakes, or the violence of the waves. Rovigliano, an island, or rather a rock, in the bay of Castel-a-Mare, is likewise of lime-stone, and seems to have belonged to the original mountains in its neighbourhood: in some of these mountains there are also petrified fish and fossil sh.e.l.ls, which I never have found in the mountains which I suppose to have been formed by explosion[34].

You have now, Sir, before you the nature of the soil, from Caprea to Naples. The soil on which this great metropolis stands has been evidently produced by explosions, some of which seem to have been upon the very spot on which this city is built; all the high grounds round Naples, Pausilipo, Puzzole, Baa, Misenum, the islands of Procita and Ischia, appear to have been raised by explosion. You can trace still in many of these heights the conical shape that was naturally given them at first, and even the craters out of which the matter issued, though to be sure others of these heights have suffered such changes by the hand of time, that you can only conjecture that they were raised in the like manner, by their composition being exactly the same as that of those mountains which still retain their conical form and craters entire. A _tufa_, exactly resembling the specimen I took from the inside of the theatre of Herculaneum, layers of pumice intermixed with layers of good soil, just like those over Pompeii, and lavas like those of Vesuvius, compose the whole soil of the country that remains to be described.

The famous grotto anciently cut through the mountain of Pausilipo, to make a road from Naples to Puzzole, gives you an opportunity of seeing that the whole of that mountain is _tufa_. The first evident crater you meet with, after you have pa.s.sed the grotto of Pausilipo, is now the lake of Agnano; a small remain of the subterraneous fire (which must probably have made the bason for the lake, and raised the high grounds which form a sort of amphitheatre round it) serves to heat rooms, which the Neapolitans make great use of in summer, for carrying off diverse disorders, by a strong perspiration. This place is called the Sudatorio di San Germano; near the present bagnios, which are but poor little hovels, there are the ruins of a magnificent ancient bath. About an hundred paces from hence is the Grotto del Cane; I shall only mention, as a further proof of the probability that the lake of Agnano was a Volcano, that vapours of a pernicious quality, as that in the Grotto del Cane, are frequently met with in the neighbourhood of Etna and Vesuvius, particularly at the time of, before, and after, great eruptions. The noxious vapour having continued in the same force constantly so many ages, as it has done in the Grotto del Cane (for Pliny mentions this Grotto[35]), is indeed a circ.u.mstance in which it differs from the vapours near Vesuvius and Etna, which are not constant.

The cone forming the outside of this supposed Volcano is still perfect in many parts.

Opposite to the Grotto del Cane, and immediately joining to the lake, rises the mountain called Astruni, which, having, as I imagine, been thrown up by an explosion of a much later date, retains the conical shape and every symptom of a Volcano in much greater perfection than that I have been describing. The crater of Astruni is surrounded with a wall, to confine boars and deers (this Volcano having been for many years converted to a royal chace). It may be about six miles or more in circ.u.mference: in the plain at the bottom of the crater are two lakes; and in some books there is mention made of a hot spring, which I never have been able to find. There are many huge rocks of lava within the crater of Astruni, and some I have met with also in that of Agnano; the cones of both these supposed Volcanos are composed of _tufa_ and strata of loose pumice, fragments of lava and other burnt matter, exactly resembling the strata of Vesuvius. Bartholomeus Fatius, who wrote of the actions of King Alphonso the First (before the new mountain had been formed near Puzzole), conjectured that Astruni had been a Volcano.

These are his words: "Locus Neapoli quatuor millia pa.s.suum proximus, quem vulgo Listrones vocant, nos unum Phlegris Campis ab ardore nuncupandum putamus." There is no entrance into the crater of either Astruni or Agnano, except one, evidently made by art, and they both exactly correspond with Strabo's description of Avernus; the same may be said of the Solfaterra and the Monte Gauro, or Barbaro as it is sometimes called, which I shall describe presently.

Near Astruni and towards the sea rises the Solfaterra, which not only retains its cone and crater, but much of its former heat. In the plain within the crater, smoak issues from many parts, as also from its sides; here, by means of stones and tiles heaped over the crevices through which the smoak pa.s.ses, they collect in an aukward manner what they call _sale armoniaco_; and from the sand of the plain they extract sulphur and alum. This spot, well attended to, might certainly produce a good revenue, whereas I doubt if they have hitherto ever cleared 200_l._ a year by it. The hollow sound produced by throwing a heavy stone on the plain of the crater of the Solfaterra seems to indicate, that it is supported by a sort of arched natural vault; and one is induced to think that there is a pool of water beneath this vault (which boils by the heat of a subterraneous fire still deeper), by the very moist steam that issues from the cracks in the plain of the Solfaterra, which, like that of boiling water, runs off a sword or knife, presented to it, in great drops. On the outside, and at the foot of the cone of the Solfaterra, towards the lake of Agnano, water rushes out of the rocks, so hot, as to raise the quicksilver in Fahrenheit's thermometer to the degree of boiling water[36], a fact of which I was myself an eye-witness. This place, well worthy the observation of the curious, has been taken little notice of; it is called the _Pisciarelli_. The common people of Naples have great faith in the efficacy of this water; and make much use of it in all cutaneous disorders, as well as for another disorder that prevails here. It seems to be impregnated chiefly with sulphur and alum.

When you approach your ear to the rocks of the Pisciarelli, from whence this water ouzes, you hear a horrid boiling noise, which seems to proceed from the huge cauldron, that may be supposed to be under the plain of the Solfaterra. On the other side of the Solfaterra, next the sea, there is a rock, which has communicated with the sea, till part of it was cut away to make the road to Puzzole; this was undoubtedly a considerable lava, that ran from the Solfaterra when it was an active Volcano. Under this rock of lava, which is more than seventy feet high, there is a stratum of pumice and ashes. This ancient lava is about a quarter of a mile broad; you meet with it abruptly before you come in sight of Puzzole, and it finishes as abruptly within about an hundred paces of the town. I have often thought that many quarries of stone, upon examination, would be found to owe their origin to the same cause, though time may have effaced all signs of the Volcano from whence they proceeded. Except this rock, which is evidently lava and full of vitrifications like that of Vesuvius, all the rocks upon the coast of Baa are of _tufa_.

I have observed in the lava of Vesuvius and Etna, as in this, that the bottom, as well as the surface of it, was rough and porous, like the cinders or scori from an iron foundery; and that for about a foot from the surface and from the bottom, they were not near so solid and compact as towards the centre; which must undoubtedly proceed from the impression of the air upon the vitrified matter whilst in fusion. I mention this circ.u.mstance, as it may serve to point out true lavas with more certainty. The ancient name of the Solfaterra was, _Forum Vulcani_; a strong proof of its origin from subterraneous fire. The degree of heat, that the Solfaterra has preserved for so many ages, seems to have calcined the stones upon its cone, and in its crater, as they are very white, and crumble easily in the hottest parts.

We come next to the new mountain near Puzzole, which, being of so very late a formation, preserves its conical shape entire, and produces as yet but a very slender vegetation. It has a crater almost as deep as the cone is high, which may be near a quarter of a mile perpendicular, and is in shape a regular inverted cone. At the basis of this new mountain (which is more than three miles in circ.u.mference), the sand upon the sea sh.o.r.e, and even that which is washed by the sea itself, is burning hot for above the s.p.a.ce of an hundred yards; if you take up a handful of the sand below water, you are obliged to get rid of it directly, on account of its intense heat.

I had been long very desirous of meeting with a good account of the formation of this new mountain, because, proving this mountain to have been raised by mere explosion in a plain, would prove at the same time, that all the neighbouring mountains, which are composed of the same materials, and have exactly or in part the same form, were raised in the like manner; and that the seat of fire, the cause of these explosions, lies deep; which I have every reason to think.

Fortunately, I lately found two very good accounts of the phnomena that attended the explosion, which formed the new mountain, published a few months after the event. As I think them very curious, and greatly to my purpose, and as they are rare, I will give you a literal translation of such extracts as relate to the formation of the Monte Nuovo. They are bound in one volume[37].

The t.i.tle of the first is, _Dell Incendio di Pozzuolo, Marco Antonio delli Falconi all Ill.u.s.trissima Signiora Marchesa della Padula nel MDx.x.xVIII_.

At the head of the second is, _Ragionamento del Terremoto, del Nuovo Monte, del Aprimento di Terra in Pozzuolo nell' Anno 1538, della significatione d'essi. Per Piero Giacomo da Toledo_; and at the end of the book, _Stampata in Nap. per Giovanni Sulztbach Alemano, a 22di Genaro 1539, con gratia, privilegio_.

"First then (says Marco Antonio delli Falconi), will I relate simply and exactly the operations of nature, of which I was either myself an eye-witness, or as they were related to me by those who had been witnesses of them. It is now two years that there have been frequent earthquakes at Pozzuolo, at Naples, and the neighbouring parts; on the day and in the night before the appearance of this eruption, above twenty shocks great and small were felt at the abovementioned places.

The eruption made its appearance the 29th of September 1538, the feast of St. Michael the angel; it was on a Sunday, about an hour in the night; and, as I have been informed, they began to see on that spot, between the hot baths or sweating rooms, and Trepergule, flames of fire, which first made their appearance at the baths, then extended towards Trepergule, and fixing in the little valley that lies between the Monte Barbaro and the hillock called del Pericolo (which was the road to the lake of Avernus and the baths), in a short time the fire increased to such a degree, that it burst open the earth in this place, and threw up so great a quant.i.ty of ashes and pumice stones mixed with water, as covered the whole country; and in Naples a shower of these ashes and water fell a great part of the night. The next morning, which was Monday, and the last of the month, the poor inhabitants of Pozzuolo, struck with so horrible a sight, quitted their habitations, covered with that muddy and black shower, which continued in that country the whole day, flying death, but with faces painted with its colours; some with their children in their arms, some with sacks full of their goods; others leading an a.s.s, loaded with their frightened family, towards Naples; others carrying quant.i.ties of birds of various sorts, that had fallen dead at the time the eruption began; others again with fish which they had found, and were to be met with in plenty upon the sh.o.r.e, the sea having been at that time considerably dried up. Don Pedro di Toledo, Viceroy of the kingdom, with many gentlemen, went to see so wonderful an appearance; I also, having met with the most honourable and incomparable gentleman, Signior Fabritio Moramaldo, on the road, went and saw the eruption and the many wonderful effects of it. The sea towards Baa had retired a considerable way; though, from the quant.i.ty of ashes and broken pumice stones thrown up by the eruption, it appeared almost totally dry. I saw likewise two springs in those lately-discovered ruins, one before the house that was the Queen's, of hot and salt water; the other of fresh and cold water, on the sh.o.r.e, about 250 paces nearer to the eruption: some say, that, still nearer to the spot where the eruption happened, a stream of fresh water issued forth like a little river. Turning towards the place of the eruption, you saw mountains of smoak, part of which was very black and part very white, rise up to a great height; and in the midst of the smoak, at times, deep-coloured flames burst forth with huge stones and ashes, and you heard a noise like the discharge of a number of great artillery. It appeared to me as if Typheus and Enceladus from Ischia and Etna with innumerable giants, or those from the Campi Phlegrei (which, according to the opinions of some, were situated in this neighbourhood), were come to wage war again with Jupiter. The natural historians may perhaps reasonably say, that the wise poets meant no more by giants, than exhalations, shut up in the bowels of the earth, which, not finding a free pa.s.sage, open one by their own force and impulse, and form mountains, as those which occasioned this eruption have been seen to do; and methought I saw those torrents of burning smoak that Pindar describes in an eruption of Etna, now called Mon Gibello, in Sicily; in imitation of which, as some say, Virgil wrote these lines:

"Ipse sed horrificis juxta tonat tna ruinis, &c.

"After the stones and ashes with clouds of thick smoak had been sent up, by the impulse of the fire and windy exhalation (as you see in a great cauldron that boils), into the middle region of the air, overcome by their own natural weight, when from distance the strength they had received from impulse was spent, rejected likewise by the cold and unfriendly region, you saw them fall thick, and, by degrees, the condensed smoak clear away, raining ashes with water and stones of different sizes, according to the distance from the place: then, by degrees, with the same noise and smoak, it threw out stones and ashes again, and so on by fits. This continued two days and nights, when the smoak and force of the fire began to abate. The fourth day, which was Thursday, at 22 o'clock, there was so great an eruption, that, as I was in the gulph of Puzzole, coming from Ischia, and not far from Misenum, I saw, in a short time, many columns of smoak shoot up, with the most terrible noise I ever heard, and, bending over the sea, came near our boat, which was four miles or more from the place of their birth; and the quant.i.ty of ashes, stones, and smoak, seemed as if they would cover the whole earth and sea. Stones, great and small, and ashes more or less, according to the impulse of the fire and exhalations, began to fall, so that a great part of this country was covered with ashes; and many, that have seen it, say, they reached the vale of Diana, and some parts of Calabria, which are more than 150 miles from Pozzuolo. The Friday and Sat.u.r.day nothing but a little smoak appeared; so that many, taking courage, went upon the spot, and say, that with the stones and ashes thrown up, a mountain has been formed in that valley, not less than three miles in circ.u.mference, and almost as high as the Monte Barbaro, which is near it, covering the Canettaria, the castle of Trepergule, all those buildings and the greatest part of the baths that were about them; extending South towards the sea, North as far as the lake of Avernus, West to the Sudatory, and joining East to the foot of the Monte Barbaro; so that this place has changed its form and face in such a manner as not to be known again: a thing almost incredible, to those who have not seen it, that in so short a time so considerable a mountain could have been formed. On its summit there is a mouth in the form of a cup, which may be a quarter of a mile in circ.u.mference, though some say it is as large as our market-place at Naples, from which there issues a constant smoak; and though I have seen it only at a distance, it appears very great. The Sunday following, which was the 6th of October, many people going to see this phnomenon, and some having ascended half the mountain, others more, about 22 o'clock there happened so sudden and horrid an eruption, with so great a smoak, that many of these people were stifled, some of which could never be found. I have been told, that the number of the dead or lost amounted to twenty-four.

From that time to this, nothing remarkable happened; it seems as if the eruption returned periodically, like the ague or gout. I believe henceforward it will not have such force, though the eruption of the Sunday was accompanied with showers of ashes and water, which fell at Naples, and were seen to extend as far as the mountain of Somma, called Vesuvius by the ancients; and, as I have often remarked, the clouds of smoak proceeding from the eruption moved in a direct line towards that mountain, as if these places had a correspondence and connection one with the other. In the night, many beams and columns of fire were seen to proceed from this eruption, and some like flashes of lightning[38].

We have then, many circ.u.mstances for our observation, the earthquakes, the eruption, the drying up of the sea, the quant.i.ty of dead fish and birds, the birth of springs, the shower of ashes with water and without water, the innumerable trees in that whole country, as far as the Grotto of Lucullus, torn from their roots, thrown down, and covered with ashes, that it gave one pain to see them: and as all these effects were produced by the same cause that produces earthquakes; let us first enquire how earthquakes are produced, and from thence we may easily comprehend the cause of the abovementioned events." Then follows a dissertation on earthquakes, and some curious conjectures relative to the phnomena which attended this eruption, clearly and well expressed, considering, as the author himself apologizes, that at that time the Italian language had been little employed on such subjects.

The account of the formation of the Monte Nuovo, by Pietro Giacomo di Toledo, is given in a dialogue between the feigned personages of Peregrino and Svessano; the former of which says, "It is now two years that this province of Campagna has been afflicted with earthquakes, the country about Pozzuolo much more so than any other parts; but the 27th and the 28th of the month of September last, the earthquakes did not cease day or night, in the abovementioned city of Pozzuolo; that plain, which lies between the lake of Averno, the Monte Barbaro, and the sea, was raised a little, and many cracks were made in it, from some of which issued water; and at the same time the sea, which was very near the plain, dried up about two hundred paces, so that the fish were left on the sand, a prey to the inhabitants of Pozzuolo. At last, on the 29th of the said month, about two hours in the night, the earth opened near the lake, and discovered a horrid mouth, from which were vomited furiously, smoak, fire, stones, and mud composed of ashes; making, at the time of its opening, a noise like very loud thunder: the fire, that issued from this mouth, went towards the walls of the unfortunate city; the smoak was partly black and partly white; the black was darker than darkness itself, and the white was like the whitest cotton: these smoaks, rising in the air, seemed as if they would touch the vault of heaven; the stones that followed were, by the devouring flames, converted to pumice, the size of which (of some I say) were much larger than an ox. The stones went about as high as a cross-bow can carry, and then fell down, sometimes on the edge, and sometimes into the mouth itself. It is very true that many of them in going up could not be seen, on account of the dark smoak; but, when they returned from the smoaky heat, they shewed plainly where they had been, by their strong smell of fetid sulphur, just like stones that have been thrown out of a mortar, and have pa.s.sed through the smoak of inflamed gunpowder. The mud was of the colour of ashes, and at first very liquid, then by degrees less so; and in such quant.i.ties, that in less than twelve hours, with the help of the abovementioned stones, a mountain was raised of a thousand paces in height. Not only Pozzuolo and the neighbouring country was full of this mud, but the city of Naples also, the beauty of whose palaces were, in a great measure, spoiled by it. The ashes were carried as far as Calabria by the force of the winds, burning up in their pa.s.sage the gra.s.s and high trees, many of which were borne down by the weight of them. An infinity of birds also, and numberless animals of various kinds, covered with this sulphureous mud, gave themselves up a prey to man. Now this eruption lasted two nights and two days without intermission, though, it is true, not always with the same force, but more or less: when it was at its greatest height, even at Naples you heard a noise or thundering like heavy artillery when two armies are engaged. The third day the eruption ceased, so that the mountain made its appearance uncovered, to the no small astonishment of every one who saw it. On this day, when I went up with many people to the top of this mountain; I saw down into its mouth, which was a round concavity of about a quarter of a mile in circ.u.mference, in the middle of which the stones that had fallen were boiling up, just as in a great cauldron of water that boils on the fire. The fourth day it began to throw up again, and the seventh much more, but still with less violence than the first night; it was at this time that many people, who were unfortunately on the mountain, were either suddenly covered with ashes, smothered with smoak, or, knocked down by stones, burnt by the flame, and left dead on the spot. The smoak continues to this day[39], and you often see in the night-time fire in the midst of it. Finally, to complete the history of this new and unforeseen event, in many parts of the new-made mountain, sulphur begins to be generated." Giacomo di Toledo, towards the end of his dissertation upon the phnomena attending this eruption, says, that the lake of Avernus had a communication with the sea, before the time of the eruption; and that he apprehended that the air of Puzzole might come to be affected in summer time, by the vapours from the stagnated waters of the lake; which is actually the case.

You have, Sir, from these accounts, an instance of a mountain, of a considerable height and dimensions, formed in a plain, by mere explosion, in the s.p.a.ce of forty-eight hours. The earthquakes having been sensibly felt at a great distance from the spot where the opening was made, proves clearly, that the subterraneous fire was at a great depth below the surface of the plain; it is as clear that those earthquakes, and the explosion, proceeded from the same cause, the former having ceased upon the appearance of the latter. Does not this circ.u.mstance evidently contradict the system of M. Buffon, and of all the natural historians, who have placed the seat of the fire of Volcanos towards the center, or near the summit of the mountains, which they suppose to furnish the matter emitted? Did the matter which proceeds from a Volcano in an eruption come from so inconsiderable a depth as they imagine, that part of the mountain situated above their supposed seat of the fire must necessarily be destroyed, or dissipated in a very short time: on the contrary, an eruption usually adds to the height and bulk of a Volcano; and who, that has had an opportunity of making observations on Volcanos, does not know, that the matter they have emitted for many ages, in lavas, ashes, smoak, &c. could it be collected together, would more than suffice to form three such mountains as the simple cone or mountain of the existing Volcano? With respect to Vesuvius, this could be plainly proved; and I refer to my letter upon the subject of Etna, to shew the quant.i.ty of matter thrown up in one single eruption, by that terrible Volcano. Another proof, that the real seat of the fire of Volcanos lies even greatly below the general level of the country whence the mountain springs, is, that was it only at an inconsiderable depth below the basis of the mountain, the quant.i.ty of matter thrown up would soon leave so great a void immediately under it, that the mountain itself must undoubtedly sink and disappear after a few eruptions.

In the above accounts of the formation of the new mountain, we are told that the matter first thrown up, was mud composed of water and ashes, mixed with pumice stones and other burnt matter: on the road leading from Puzzole to c.u.ma, part of the cone of this mountain has been cut away, to widen the road. I have there seen that its composition is a _tufa_ intermixed with pumice, some of which are really of the size of an ox, as mentioned in Toledo's account, and exactly of the same nature as the _tufa_ of which every other high ground in its neighbourhood is composed; similar also to that which covers Herculaneum. According to the above accounts, after the muddy shower ceased, it rained dry ashes: this circ.u.mstance will account for the strata of loose pumice and ashes, that are generally upon the surface of all the _tufas_ in this country, and which were most probably thrown up in the same manner. At the first opening of the earth, in the plain near Puzzole, both accounts say, that springs of water burst forth; this water, mixing with the ashes, certainly occasioned the muddy shower; when the springs were exhausted, there must naturally have ensued a shower of dry ashes and pumice, of which we have been likewise a.s.sured. I own, I was greatly pleased at being in this manner enabled to account so well for the formation of these _tufa_ stones and the veins of dry and loose burnt matter above them, of which the soil of almost the whole country I am describing is composed; and I do not know that any one has ever attended to this circ.u.mstance, though I find that many authors, who have described this country, have suspected that parts of it were formed by explosion.

Wherever then this sort of _tufa_ is found, there is certainly good authority to suspect its having been formed in the same manner as the _tufa_ of this new mountain, for, as I said before, Nature is generally uniform in all her operations.

It is commonly imagined that the new mountain rose out of the Lucrine lake, which was destroyed by it; but in the above account, no mention is made of the Lucrine lake; it may be supposed then, that the famous dam, which Strabo and many other ancient authors mention to have separated that lake from the sea, had been ruined by time or accident, and that the lake became a part of the sea before the explosion of 1538.

If the above-described eruption was terrible, that which formed the Monte Barbaro (or Gauro, as it was formerly called), must have been dreadful indeed. It joins immediately to the new mountain, which in shape and composition it exactly resembles; but it is at least three times as considerable. Its crater cannot be less than six miles in circ.u.mference; the plain within the crater, one of the most fertile spots I ever saw, is about four miles in circ.u.mference: there is no entrance to this plain, but one on the East side of the mountain, made evidently by art; in this section you have an opportunity of seeing that the matter of which the mountain is composed is exactly similar to that of the Monte Nuovo. It was this mountain that produced (as some authors have supposed) the celebrated Falernian wine of the ancients.

c.u.ma, allowed to have been the most ancient city of Italy, was built on an eminence, which is likewise composed of _tufa_, and may be naturally supposed a section of the cone formed by a very ancient explosion.

The lake of Avernus fills the bottom of the crater of a mountain, undoubtedly produced by explosion, and whose interior and exterior form, as well as the matter of which it is composed, exactly resemble the Monte Barbaro and Monte Nuovo. At that part of the basis of this mountain which is washed by the sea of the bay of Puzzole, the sand is still very hot, though constantly washed by the waves; and into the cone of the mountain, near this hot sand, a narrow pa.s.sage of about 100 paces in length is cut, and leads to a fountain of boiling water, which, though brackish, boils fish and flesh without giving them any bad taste or quality, as I have experienced more than once. This place is called Nero's bath, and is still made use of for a sudatory, as it was by the ancients; the steam that rises from the hot fountain abovementioned, confined in the narrow subterraneous pa.s.sage, soon produces a violent perspiration upon the patient who sits therein. This bath is reckoned a great specifick in that distemper which is supposed to have made its appearance at Naples before it spread its contagion over the other parts of Europe.

Virgil and other ancient authors say, that birds could not fly with safety over the lake of Avernus, but that they fell therein; a circ.u.mstance favouring my opinion, that this was once the mouth of a Volcano. The vapour of the sulphur and other minerals must undoubtedly have been more powerful, the nearer we go back to the time of the explosion of the Volcano; and I am convinced that there are still some remains of those vapours upon this lake, as I have observed there are very seldom any water-fowl upon it; and that when they do go there, it is but for a short time; whilst all the other lakes in the neighbourhood are constantly covered with them, in the winter season. Upon Mount Vesuvius, in the year 1766, during an eruption, when the air was impregnated with noxious vapours, I have myself picked up dead birds frequently.

The castle of Baa stands upon a considerable eminence, composed of the usual _tufa_ and strata of pumice and ashes; from which I concluded I should find some remains of the craters from whence the matter issued: accordingly, having ascended the hill, I soon discovered two very visible craters, just behind the castle.

The lake called the Mare-morto was also, most probably, the crater, from whence issued the materials which formed the Promontory of Misenum, and the high grounds around this lake. Under the ruins of an ancient building, near the point of Misenum, in a vault, there is a vapour, or _mofete_, exactly similar in its effects to that of the Grotto del Cane, as I have often experienced.

The form of the little island of Nisida shews plainly its origin[40]. It is half a hollow cone of a Volcano cut perpendicularly; the half crater forms a little harbour called the Porto Pavone; I suppose the other half of the cone to have been detached into the sea by earthquakes, or perhaps by the violence of the waves, as the part that is wanting is the side next to the open sea.

The fertile and pleasant island of Procita shews also most evident signs of its production by explosion, the nature of its soil being directly similar to that of Baa and Puzzole; this island seems really, as was imagined by the ancients, to have been detached from the neighbouring island of Ischia.