Principles of Geology Part 42

There have undoubtedly been instances in Calabria and elsewhere of slides of land on which the houses have still remained standing; and it is possible that such may have been the case at Port Royal. The fact at least of submergence is unquestionable, for I was informed by the late Admiral Sir Charles Hamilton that he frequently saw the submerged houses of Port Royal in the year 1780, in that part of the harbor which lies between the town and the usual anchorage of men-of-war. Bryan Edwards also says, in his history of the West Indies, that in 1793 the _ruins_ were visible in clear weather from the boats which sailed over them.[708] Lastly, Lieutenant B. Jeffery, R. N., tells me that, being engaged in a survey between the years 1824 and 1835, he repeatedly visited the site in question, where the depth of the water is from four to six fathoms, and whenever there was but little wind perceived distinct traces of houses. He saw these more clearly when he used the instrument called the "diver's eye," which is let down below the ripple of the wave.[709]

At several thousand places in Jamaica the earth is related to have opened. On the north of the island several plantations, with their inhabitants, were swallowed up, and a lake appeared in their place, covering above a thousand acres, which afterwards dried up, leaving nothing but sand and gravel, without the least sign that there had ever been a house or a tree there. Several tenements at Yallows were buried under land-slips; and one plantation was removed half a mile from its place, the crops continuing to grow upon it uninjured. Between Spanish Town and Sixteen-mile Walk, the high and perpendicular cliffs bounding the river fell in, stopped the pa.s.sage of the river and flooded the latter place for nine days, so that the people "concluded it had been sunk as Port Royal was." But the flood at length subsided, for the river had found some new pa.s.sage at a great distance.

_Mountains shattered._--The Blue and other of the highest mountains are declared to have been strangely torn and rent. They appeared shattered and half-naked, no longer affording a fine green prospect, as before, but stripped of their woods and natural verdure. The rivers on these mountains first ceased to flow for about twenty-four hours, and then brought down into the sea, at Port Royal and other places, several hundred thousand tons of timber, which looked like floating islands on the ocean. The trees were in general barked, most of their branches having been torn off in the descent. It is particularly remarked in this, as in the narratives of so many earthquakes, that fish were taken in great numbers on the coast during the shocks. The correspondents of Sir Hans Sloane, who collected with care the accounts of eye-witnesses of the catastrophe, refer constantly to _subsidences_, and some supposed the whole of Jamaica to have sunk down.[710]

_Reflections on the amount of change in the last one hundred and sixty years._--I have now only enumerated some few of the earthquakes of the last 160 years, respecting which facts ill.u.s.trative of geological inquiries are on record. Even if my limits permitted, it would be an unprofitable task to examine all the obscure and ambiguous narratives of similar events of earlier epochs; although, if the places were now examined by geologists well practised in the art of interpreting the monuments of physical changes, many events which have happened within the historical era might doubtless be still determined with precision.

It must not be imagined that, in the above sketch of the occurrences of a short period, I have given an account of all, or even the greater part, of the mutations which the earth has undergone by the agency of subterranean movements. Thus, for example, the earthquake of Aleppo, in the present century, and of Syria, in the middle of the eighteenth, would doubtless have afforded numerous phenomena, of great geological importance, had those catastrophes been described by scientific observers. The shocks in Syria in 1759, were protracted for three months, throughout a s.p.a.ce of ten thousand square leagues: an area compared to which that of the Calabrian earthquake in 1783 was insignificant. Accon, Saphat, Balbeck, Damascus, Sidon, Tripoli, and many other places, were almost entirely levelled to the ground. Many thousands of the inhabitants perished in each; and, in the valley of Balbeck alone, 20,000 men are said to have been victims to the convulsion. In the absence of scientific accounts, it would be as irrelevant to our present purpose to enter into a detailed account of such calamities, as to follow the track of an invading army, to enumerate the cities burnt or rased to the ground, and reckon the number of individuals who perished by famine or the sword.

_Deficiency of historical records._--If such, then, be the amount of ascertained changes in the last 160 years, notwithstanding the extreme deficiency of our records during that brief period, how important must we presume the physical revolutions to have been in the course of thirty or forty centuries, during which some countries habitually convulsed by earthquakes have been peopled by civilized nations! Towns engulfed during one earthquake may, by repeated shocks, have sunk to great depths beneath the surface, while the ruins remain as imperishable as the hardest rocks in which they are inclosed. Buildings and cities, submerged, for a time, beneath seas or lakes, and covered with sedimentary deposits, must, in some places, have been re-elevated to considerable heights above the level of the ocean. The signs of these events have, probably, been rendered visible by subsequent mutations, as by the encroachments of the sea upon the coast, by deep excavations made by torrents and rivers, by the opening of new ravines, and chasms, and other effects of natural agents, so active in districts agitated by subterranean movements.

If it be asked why, if such wonderful monuments exist, so few have hitherto been brought to light, we reply--because they have not been searched for. In order to rescue from oblivion the memorials of former occurrences, the inquirer must know what he may reasonably expect to discover, and under what peculiar local circ.u.mstances. He must be acquainted with the action and effect of physical causes, in order to recognize, explain, and describe correctly the phenomena when they present themselves.

The best known of the great volcanic regions, of which the boundaries were sketched in the twenty-second chapter, is that which includes Southern Europe, Northern Africa, and Central Asia; yet nearly the whole, even of this region, must be laid down, in a geological map, as "Terra Incognita." Even Calabria may be regarded as unexplored, as also Spain, Portugal, the Barbary States, the Ionian Isles, Asia Minor, Cyprus, Syria, and the countries between the Caspian and Black seas. We are, in truth, beginning to obtain some insight into one small spot of that great zone of volcanic disturbance, the district around Naples; a tract by no means remarkable for the violence of the earthquakes which have convulsed it.

If, in this part of Campania, we are enabled to establish that considerable changes in the relative level of land and sea have taken place since the Christian era, it is all that we could have expected; and it is to recent antiquarian and geological research, not to history, that we are princ.i.p.ally indebted for the information. I shall now proceed to lay before the reader some of the results of modern investigations in the Bay of Baiae and the adjoining coast.

PROOFS OF ELEVATION AND SUBSIDENCE IN THE BAY OF BAIae.

[Ill.u.s.tration: Fig. 86.

Ground plan of the coast of the Bay of Baiae, in the environs of Puzzuoli.]

_Temple of Jupiter Serapis._--This celebrated monument of antiquity, a representation of which is given in the frontispiece,[711] affords in itself alone, unequivocal evidence that the relative level of land and sea has changed twice at Puzzuoli since the Christian era; and each movement, both of elevation and subsidence, has exceeded twenty feet.

Before examining these proofs, I may observe, that a geological examination of the coast of Baiae, both on the north and south of Puzzuoli, establishes, in the most satisfactory manner, an elevation, at no remote period, of more than twenty feet, and, at one point, of more than thirty feet; and the evidence of this change would have been complete, if even the temple had, to this day, remained undiscovered.

_Coast south of Puzzuoli._--If we coast along the sh.o.r.e from Naples to Puzzuoli, we find, on approaching the latter place, that the lofty and precipitous cliffs of indurated tuff, resembling that of which Naples is built, retire slightly from the sea; and that a low level tract of fertile land, of a very different aspect, intervenes between the present sea-beach and what was evidently the ancient line of coast.

The inland cliff may be seen opposite the small island of Nisida, about two miles and a half southeast of Puzzuoli (see Map, fig. 40, p. 361), where, at the height of thirty-two feet above the level of the sea, Mr.

Babbage observed an ancient mark, such as might have been worn by the waves; and, upon farther examination, discovered that, along that line, the face of the perpendicular rock, consisting of very hard tuff, was covered with barnacles (_Bala.n.u.s sulcatus_, Lamk.), and drilled by boring testacea. Some of the hollows of the lithodomi contained the sh.e.l.ls; while others were filled with the valves of a species of Area.[712] Nearer to Puzzuoli, the inland cliff is eighty feet high, and as perpendicular as if it was still undermined by the waves. At its base, a new deposit, const.i.tuting the fertile tract above alluded to, attains a height of about twenty feet above the sea; and, since it is composed of regular sedimentary deposits, containing marine sh.e.l.ls, its position proves that, subsequently to its formation, there has been a change of more than twenty feet in the relative level of land and sea.

[Ill.u.s.tration: Fig. 87.

_a_, Antiquities on hill S. E. of Puzzuoli (see ground plan, fig. 86).

_b_, Ancient cliff now inland.

_c_, Terrace composed of recent submarine deposit.]

The sea encroaches on these new incoherent strata; and as the soil is valuable, a wall has been built for its protection; but when I visited the spot in 1828, the waves had swept away part of this rampart, and exposed to view a regular series of strata of tuff, more or less argillaceous, alternating with beds of pumice and lapilli, and containing great abundance of marine sh.e.l.ls, of species now common on this coast, and amongst them _Cardium rustic.u.m_, _Ostrea edulis_, _Donax trunculus_, Lamk., and others. The strata vary from about a foot to a foot and a half in thickness, and one of them contains abundantly remains of works of art, tiles, squares of mosaic pavement of different colors, and small sculptured ornaments, perfectly uninjured.

Intermixed with these I collected some teeth of the pig and ox. These fragments of building occur below as well as above strata containing marine sh.e.l.ls. Puzzuoli itself stands chiefly on a promontory of the older tufaceous formation, which cuts off the new deposit, although I detected a small patch of the latter in a garden under the town.

[Ill.u.s.tration: Fig. 88.

VIEW OF BAY OF BAIae.

1. Puzzuoli. 2. Temple of Serapis. 3. Caligula's Bridge 4. Monte Barbaro. 5. Monte Nuovo. 6. Baths of Nero. 7. Baiae.

8. Castle of Baiae. 9. Bauli. 10. Cape Misenum. 11. Mount Epomeo in Ischia. 12. South Part of Ischia.

From the town the ruins of a mole, called Caligula's Bridge, run out into the sea (see fig. 88, p. 509).[713] This mole, which is believed to be eighteen centuries old, consists of a number of piers and arches, thirteen of which are now standing, and two others appear to have been overthrown. Mr. Babbage found, on the sixth pier, perforations of lithodomi four feet above the level of the sea; and, near the termination of the mole on the last pier but one, marks of the same, ten feet above the level of the sea, together with great numbers of balani and fl.u.s.tra. The depth of the sea, at a very small distance from most of the piers, is from thirty to fifty feet.

[Ill.u.s.tration: Fig. 89.

_a_, Remains of Cicero's villa, N. side of Puzzuoli.[714]

_b_, Ancient cliff now inland.

_c_, Terrace (called La Starza) composed of recent submarine deposits.

_d_, Temple of Serapis.

_Coast north of Puzzuoli._--If we then pa.s.s to the north of Puzzuoli, and examine the coast between that town and Monte Nuovo, we find a repet.i.tion of a.n.a.logous phenomena. The sloping sides of Monte Barbaro slant down within a short distance of the coast, and terminate in an inland cliff of moderate elevation, to which the geologist perceives at once that the sea must, at some former period, have extended. Between this cliff and the sea is a low plain or terrace, called La Starza (_c_, fig. 89), corresponding to that before described on the southeast of the town; and as the sea encroaches rapidly, fresh sections of the strata may readily be obtained, of which the annexed is an example.

Section on the sh.o.r.e north of the town of Puzzuoli:--

Ft. In.

1. Vegetable soil 1 0

2. Horizontal beds of pumice and scoriae, with broken fragments of unrolled bricks, bones of animals, and marine sh.e.l.ls 1 6

3. Beds of lapilli, containing abundance of marine sh.e.l.ls, princ.i.p.ally _Cardium rustic.u.m_, _Donax trunculus_, Lam., _Ostrea edulis_, _Triton cutaceum_, Lam., and _Buccinum serratum_, Brocchi, the beds varying in thickness from one to eighteen inches 10 0

4. Argillaceous tuff, containing bricks and fragments of buildings not rounded by attrition. 1 6

The thickness of many of these beds varies greatly as we trace them along the sh.o.r.e, and sometimes the whole group rises to a greater height than at the point above described. The surface of the tract which they compose appears to slope gently upwards towards the base of the old cliffs.

Now, if such appearances presented themselves on the coast of England, a geologist might endeavor to seek an explanation in some local change in the set of the tides and currents: but there are scarce any tides in the Mediterranean; and, to suppose the sea to have sunk generally from twenty to twenty-five feet since the sh.o.r.es of Campania were covered with sumptuous buildings is an hypothesis obviously untenable. The observations, indeed, made during modern surveys on the moles and cothons (docks) constructed by the ancients in various ports of the Mediterranean, have proved that there has been no sensible variation of level in that sea during the last two thousand years.[715]

Thus we arrive, without the aid of the celebrated temple, at the conclusion, that the recent marine deposit at Puzzuoli was upraised in modern times above the level of the sea, and that not only this change of position, but the acc.u.mulation of the modern strata, was posterior to the destruction of many edifices, of which they contain the imbedded remains. If we next examine the evidence afforded by the temple itself, it appears, from the most authentic accounts, that the three pillars now standing erect continued, down to the middle of the last century, almost buried in the new marine strata (_c_, fig. 89). The upper part of each protruding several feet above the surface was concealed by bushes, and had not attracted, until the year 1749, the notice of antiquaries; but, when the soil was removed in 1750, they were seen to form part of the remains of a splendid edifice, the pavement of which was still preserved, and upon it lay a number of columns of African breccia and of granite. The original plan of the building could be traced distinctly: it was of a quadrangular form, seventy feet in diameter, and the roof had been supported by forty-six n.o.ble columns, twenty-four of granite and the rest of marble. The large court was surrounded by apartments, supposed to have been used as bathing-rooms; for a thermal spring, still used for medicinal purposes, issues just behind the building, and the water of this spring appears to have been originally conveyed by a marble duct, still extant, into the chambers, and then across the pavement by a groove an inch or two deep, to a conduit made of Roman brickwork, by which it gained the sea.

Many antiquaries have entered into elaborate discussions as to the deity to which this edifice was consecrated. It is admitted that, among other images found in excavating the ruins, there was one of the G.o.d Serapis; and at Puzzuoli a marble column was dug up, on which was carved an ancient inscription, of the date of the building of Rome 648 (or B. C.

105), ent.i.tled "Lex parieti faciundo." This inscription, written in very obscure Latin, sets forth a contract, between the munic.i.p.ality of the town, and a company of builders who undertook to keep in repair certain public edifices, the Temple of Serapis being mentioned amongst the rest, and described as being near or towards the sea, "mare vorsum."

Sir Edmund Head, after studying, in 1828, the topography and antiquities of this district, and the Greek, Roman, and Italian writers on the subject, informed me, that at Alexandria, on the Nile, the chief seat of the wors.h.i.+p of Serapis, there was a Serapeum of the same form as this temple at Puzzuoli, and surrounded in like manner by chambers, in which the devotees were accustomed to pa.s.s the night, in the hope of receiving during sleep a revelation from the G.o.d, as to the nature and cure of their diseases. Hence it was very natural that the priests of Serapis, a pantheistic divinity, who, among other usurpations, had appropriated to himself the attributes of Esculapius, should regard the hot spring as a suitable appendage to the temple, although the original Serapeum of Alexandria could boast no such medicinal waters. Signor Carelli[716] and others, in objecting to these views, have insisted on the fact, that the wors.h.i.+p of Serapis, which we know prevailed at Rome in the days of Catullus (in the first century before Christ), was prohibited by the Roman Senate, during the reign of the Emperor Tiberius. But there is little doubt that, during the reigns of that emperor's successors, the shrines of the Egyptian G.o.d were again thronged by zealous votaries; and in no place more so than at Puteoli (now Puzzuoli), one of the princ.i.p.al marts for the produce of Alexandria.

Without entering farther into an inquiry which is not strictly geological, I shall designate this valuable relic of antiquity by its generally received name, and proceed to consider the memorials of physical changes inscribed on the three standing columns in most legible characters by the hand of Nature. (See Frontispiece.) These pillars, which have been carved each out of a single block of marble, are forty feet three inches and a half in height. A horizontal fissure nearly intersects one of the columns; the other two are entire. They are all slightly out of the perpendicular, inclining somewhat to the southwest, that is, towards the sea.[717] Their surface is smooth and uninjured to the height of about twelve feet above their pedestals. Above this is a zone, about nine feet in height, where the marble has been pierced by a species of marine perforating bivalve--_Lithodomus_, Cuv.[718] The holes of these animals are pear-shaped, the external opening being minute, and gradually increasing downwards. At the bottom of the cavities, many sh.e.l.ls are still found, notwithstanding the great numbers that have been taken out by visitors; in many the valves of a species of arca, an animal which conceals itself in small hollows, occur. The perforations are so considerable in depth and size, that they manifest a long-continued abode of the lithodomi in the columns, for, as the inhabitant grows older and increases in size, it bores a larger cavity, to correspond with the increased magnitude of its sh.e.l.l. We must, consequently, infer a long-continued immersion of the pillars in sea-water, at a time when the lower part was covered up and protected by marine, fresh-water, and volcanic strata, afterwards to be described, and by the rubbish of buildings; the highest part, at the same time, projecting above the waters, and being consequently weathered, but not materially injured. (See fig. 90, p. 514.)

On the pavement of the temple lie some columns of marble, which are also perforated in certain parts; one, for example, to the length of eight feet, while, for the length of four feet, it is uninjured. Several of these broken columns are eaten into, not only on the exterior, but on the cross fracture, and, on some of them, other marine animals (serpulae, &c.) have fixed themselves.[719] All the granite pillars are untouched by lithodomi. The platform of the temple, which is not perfectly even, was, when I visited it in 1828, about one foot below high-water mark (for there are small tides in the bay of Naples); and the sea, which was only one hundred feet distant, soaked through the intervening soil. The upper part of the perforations, therefore, were at least twenty-three feet above high-water mark; and it is clear that the columns must have continued for a long time in an erect position, immersed in salt water, and then the submerged portion must have been upraised to the height of about twenty-three feet above the level of the sea.

By excavations carried on in 1828, below the marble pavement on which the columns stand, another costly pavement of mosaic was found, at the depth of about five feet below the upper one (_a_, _b_, fig. 90). The existence of these two pavements, at different levels, clearly implies some subsidence previously to the building of the more modern temple which had rendered it necessary to construct the new floor at a higher level.

[Ill.u.s.tration: Fig. 90.

Temple of Serapis at its period of greatest depression.