Part 24

The inhabitants of Adria have formed exaggerated pretensions, in many respects, as to the high antiquity of their city, though it is undeniably one of the most ancient in Italy, as it gave name to the sea which once washed its walls. By some researches made in its interior and its environs, a stratum of earth has been found mixed with fragments of Etruscan pottery, and with nothing whatever of Roman manufacture. Etruscan and Roman pottery are found mixed together in a superior bed, on the top of which the vestiges of a theatre have been discovered. Both of these beds are far below the level of the present soil. I have seen at Adria very curious collections, in which these remains of antiquity are separately classed; and having, some years ago, observed to the viceroy, that it would be of great importance, both to history and geology, to make a thorough search into these buried remains at Adria, carefully noticing the levels in comparison with the sea, both of the primitive soil, and of the successive alluvial beds, his Highness entered warmly into my ideas; but I know not whether these propositions have been since carried into effect.

Following the coast, after leaving Hatria, which was situated at the bottom of a small bay or gulf, we find to the south a branch of the _Athesis_ or Adige, and of the _Fossa Philistina_, of which the remaining trace corresponds to what might have been the Mincio and Tartaro united, if the Po had still run to the south of Ferrara. We next find the _Delta Venetum_, which seems to have occupied the place where the lake or lagune of Commachio is now situated. This delta was traversed by seven branches of the _Eridanus_ or Po, formerly called also the _Vadis Padus_ or _Podincus_; which river, at the diramification of these seven branches, and upon its left or northern bank, had a city named _Trigoboli_, whose site could not be far from where Ferrara now stands. Seven lakes, inclosed within this delta, were called _Septem Maria_, and Hatria was sometimes denominated _Urbs Septem Marium_, or the city of the seven seas or lakes.

Following the coast from Hatria to the northwards, we come to the principal mouth of the _Athesis_ or Adige, formerly named _Fossa Philistina_, and afterwards _Estuarium Altini_, an interior sea, separated by a range of small islands from the Adriatic Gulf, in the middle of which was a cluster of other small isles, called _Rialtum_, and upon this archipelago the city of Venice is now seated. The _Estuarium Altini_ is what is now called the Lagune of Venice, and no longer communicates with the sea, except by five passages, the small islands of the Archipelago having been united into a continuous dike.

To the east of the lagunes, and north from the city of Este, we find the _Euganian_ mountains, or hills, forming, in the midst of a vast alluvial plain, a remarkable isolated group of rounded hills, near which spot the fable of the ancients supposes the fall of Phæton to have taken place. Some writers have supposed that this fable may have originated from the fall of some vast masses of inflamed matters near the mouths of the Eridanus, that had been thrown up by a volcanic explosion; and it is certain that abundance of volcanic products are found in the neighbourhood of Padua and Verona.

The most ancient notices that I have been able to procure respecting the situation of the shores of the Adriatic at the mouths of the Po, only begin to be precise in the twelfth century. At that epoch the whole waters of this river flowed to the south of Ferrara, in the _Po de Volano_ and the _Po di Primaro_, branches which inclosed the space occupied by the _lagune_ of Commachio. The two branches which were next formed by an irruption of the waters of the Po to the north of Ferraro, were named the river of _Corbola_, _Longola_, or _Mazzorno_, and the river _Toi_. The former, and more northern of these, received the _Tartaro_, or _canal bianco_, near the sea, and the latter was joined at Ariano by another branch derived from the Po, called the _Goro river_. The sea-coast was evidently directed from south to north, at the distance of ten or eleven thousand _metres_[388] from the meridian of Adria; and _Loreo_, to the north of _Mesola_, was only about 2000 _metres_[389] from the coast.

Towards the middle of the twelfth century, the flood-waters of the Po were retained on their left or northern side by dikes near the small city of _Ficarolo_, which is about 19,000 _metres_[390] to the north-west of Ferrara, spreading themselves southwards over the northern part of the territory of Ferrara and the _Polesine_ of Rovigo, and flowed through the two formerly mentioned canals of _Mazzorno_ and _Toi_. It seems perfectly ascertained, that this change in the direction of the waters of the Po had been produced by the effects of human labours; and the historians who have recorded this remarkable fact only differ from each other in some of the more minute details. The tendency of the river to flow in the new channels, which had been opened for the more ready discharge of its waters when in flood, continually increased; owing to which the two ancient chief branches, the _Volano_ and _Primaro_, rapidly decreased, and were reduced in less than a century to their present comparatively insignificant size; while the main direction of the river was established between the mouth of the Adige to the north, and what is now called _Porto di Goro_, on the south. The two before-mentioned canals of _Mazzorno_ and _Toi_ becoming insufficient for the discharge, others were dug; and the principal mouth, called _Bocco Tramontana_, or the northern mouth, having approached the mouth of the Adige, the Venetians became alarmed in 1604; when they excavated a new canal of discharge, named _Taglio de Porto Viro_, or _Po delle Fornaci_, by which means the _Bocco Maestra_, was diverted from the Adige towards the south.

During four centuries, from the end of the twelfth to that of the sixteenth, the alluvial formations of the Po gained considerably upon the sea. The northern mouth, which had usurped the situation of the _Mazzorno_ canal, becoming the _Rama di Trimontana_, had advanced in 1600 to the distance of 20,000 _metres_[391] from the meridian of Adria; and the southern mouth, which had taken possession of the canal of _Toi_, was then 17,000 _metres_[392] advanced beyond the same point. Thus the shore had become extended nine or ten thousand _metres_[393] to the north, and six or seven thousand to the south[394]. Between these two mouths there was formerly a bay, or a part of the coast less advanced than the rest, called _Sacca di Goro_. During the same period of four hundred years previous to the commencement of the seventeenth century, the great and extensive embankments of the Po were constructed; and also, during the same period, the southern slopes of the Alps began to be cleared and cultivated.

The great canal, denominated _Taglio di Porto Viro_, or _Po delle Fornaci_, ascertains the advance of the alluvial depositions in the vast promontory now formed by the mouths or delta of the Po. In proportion as their entrances into the sea extend from the original land, the yearly quantity of alluvial depositions increases in an alarming degree, owing to the diminished slope of the streams, which was a necessary consequence, of the prolongation of their bed, to the confinement of the waters between dikes, and to the facility with which the increased cultivation of the ground enabled the mountain torrents which flowed into them to carry away the soil. Owing to these causes, the bay called _Sacra di Goro_ was very soon filled up, and the two promontories which had been formed by the two former principal mouths of _Mazzorno_ and _Toi_, were united into one vast projecting cape, the most advanced point of which is now 32,000 or 33,000 _metres_[395] beyond the meridian of Adria: so that in the course of two hundred years, the mouths or delta of the Po have gained about 14,000 _metres_[396] upon the sea.

From all these facts, of which I have given a brief enumeration, the following results are clearly established.

_First_, That, at some ancient period, the precise date of which cannot be now ascertained, the waves of the Adriatic washed the walls of Adria.

_Secondly_, That, in the twelfth century, before a passage had been opened for the waters of the Po at _Ficarrolo_; on its left or northern bank, the shore had been already removed to the distance of nine or ten thousand _metres_[397] from Adria.

_Thirdly_, That the extremities of the promontories formed by the two principal branches of the Po, before the excavation of the _Taglio di Porto Viro_, had extended, by the year 1600, or in four hundred years, to a medium distance of 18,500 _metres_[398] beyond Adria; giving, from the year 1200, an average yearly increase of the alluvial land of 25 _metres_[399].

_Fourthly_, That the extreme point of the present single promontory, formed by the alluvions of the existing branches, is advanced to between thirty-two and thirty-three thousand _metres_[400] beyond Adria; whence the average yearly progress is about seventy _metres_[401] during the last two hundred years, being a greatly more rapid proportion than in former times.

PRONY.

NOTE, p. 244.

_On the Universal Deluge._

Mr Cuvier in the present work, and more recently in a note to Mr Lemaire’s edition of Ovid’s Metamorphoses, enumerates the Mosaic, Grecian, Assyrian, Persian, Indian, and Chinese traditions, concerning a universal deluge; and concludes from them, that the surface of the globe, five or six thousand years ago, underwent a general and sudden revolution, by which the lands inhabited by the human beings who lived at that time, and by the various species of animals known at the present day, were overflowed by the ocean; out of which emerged the present habitable portions of the globe. This celebrated naturalist maintains, that these regions of the earth were peopled by the few individuals who were preserved, and that the tradition of the catastrophe has been preserved among these new races of people, variously modified by the difference of their situation and their social disposition. According to Mr Cuvier, similar revolutions of nature had taken place, at periods long antecedent to that of the Mosaic deluge. The dry land was inhabited, if not by human beings, at least by land animals at an earlier period; and must have been changed from the dry land to the bed of the ocean; and it might even be concluded from the various species of animals contained in it, that this change, as well as its opposite, had occurred more than once.

This opinion being brought forward in a geognostic work, especially in a work abounding in such valuable matters of fact, and stated as the result of geognostic investigation, we may be permitted, in this point of view, to examine it; and to ask, whether, from the phenomena exhibited by the present condition of the earth’s surface, we are entitled to conclude that it owes its conformation to such a universal deluge.

We know, from arguments suggested by chemistry and the higher mechanics, that the globe was once in a state of fluidity; hence it might be maintained with some appearance of probability, that the condition of the earth, previous to the existence of organic matter, depended upon fusion; and that the primitive rocks are of igneous origin. Since, however, granite has been found above rocks of various kinds which contain the remains of organic bodies, we are under no necessity of ascribing to primitive rocks an origin different from that of subsequent formations; and, without having recourse to other arguments, the fact, that aquatic animals are the most abundant of fossil organic remains from the earliest of the transition to the latest of the secondary and tertiary formations, affords evidence that they are precipitates from water.

Notwithstanding the great and daily advancement of science, our knowledge of chemistry is still too imperfect for us to arrive at an adequate knowledge of the state of this water, or rather sea, as, from its universal expansion, it must be denominated. Did it contain dissolved in it at the same time all the materials from which the various beds of rock were formed; what were the solvents of those materials which we find, either insoluble in water, or at least not easily soluble; by what means were the precipitates produced; and whence came this prodigious mass of waters? Upon these unanswered questions depend others no less important. The aquatic animals of a former world undoubtedly lived in this sea; otherwise, we must admit of another sea free from heterogeneous materials. But did these animals continue to live in it during the whole process of precipitation; and did this process proceed so slowly and imperceptibly, that animal life was not interrupted by it, and that only remains of dead animals, such as the skeletons of fishes, and the covering of shell-fishes, were enveloped in the precipitates? Or, did animal life continue only during the state of solution; and were the myriads of aquatic animals found in beds of rocks buried in them alive? Many naturalists appear to entertain the latter opinion, from observing the agonies of death depicted in the distorted position of fishes in copper-slate, or from deriving the bituminous properties of stink-stone, as well as of marl, from the decomposition of animal bodies, of which such numerous vestiges are extant in these beds? In this way a plausible explanation is given of the phenomena of a former world that has perished. How, then, do they explain the constant appearance of so many species, which have continued without interruption for such an infinite length of time? Have these species been propagated by individuals who accidentally escaped destruction: or, Does a new race continually spring up again? But laying aside the difficulty of this explanation, the violent destruction of so many races of animals, is scarcely consistent with the general order of the universe, according to which, we behold every animal occupying its proper element, and fulfilling its particular destiny. We, therefore, involuntarily revert to the opinion, that those creatures, whose remains are preserved in beds of rocks, have lived continually in the sea, out of which the rocks were precipitated, in the same manner as the analogous species now living in the sea become enveloped in deposits still taking place, although on a comparatively small scale.

What has just been said does not entitle us to admit that the various parts of the earth have been, from time to time, overflowed with water. Yet are there other appearances which completely indicate such a change, namely, beds of coal, and the fossil remains of land animals. The carbonisation of roots of trees in clefts of rocks, and of marsh plants in peat-bogs, which takes place, as it were, under our own immediate observation; the transitions of bituminous wood into pitch-coal, the frequent presence of vegetables partly converted into coal, in the neighbourhood of beds of coal, and which are more abundant the nearer they are to these beds; and, finally, the chemical nature of coal, which is similar to that of vegetables, go to prove the vegetable origin of the older and independent coal formation.

Though some fossil vegetables might derive their origin, by being floated to quarters more or less remote from their native soil, as we find to be the case in many islands of the South Sea, and on other shores; on the other hand, neither the breadth and extent of beds of coal, nor the erect position in which fossil trees and reed plants are not unfrequently found in their neighbourhood, coincide with such an explanation. The plants, from which these beds were formed, once stood and grew in the place where they were buried; and, from these remains, we infer that they were entirely land plants, tree-ferns, _Lycopodia_, and other cryptogamia. It also appears undeniable, that the land, being once dry, was, during a longer or shorter time, covered with luxuriant vegetation; that it was afterwards overflowed with water, and then became dry land again. But, was this overflow of water produced by a sudden, violent, and universal catastrophe, such as we consider the deluge? Many circumstances leave room for opposite conjecture. If it is probable that the older or black coal is of vegetable origin, the plants from which it has originated, must have suffered an incomparably greater change than those of more recent coal formations. Their composition and their texture, afford evidence of a long operation of the fluid in which the changes were produced; and their situation, proves that the substance of the plants, though not entirely dissolved, was yet much comminuted, and was kept floating and swimming, and then precipitated. How can we, in any other way, account for the layers of sandstone and slate-clay, with which coal regularly alternates, so that from one to sixty alternate beds have been enumerated? How can we explain the combination of mineral coal with slate-clay, or account for the appearance of bituminous shale, flinty slate, of iron-pyrites and iron-ore, in the midst of mineral coal itself? We do not, however, admit of a repeated uncovering and covering of the land with water, and of a renewal of vegetation for every particular bed of coal; far from it, for violent inundations exhibit very different phenomena. These formations, like pure mineral formations, bear the evident impress of a lengthened operation, and of gentle precipitations; and whoever still entertains doubts regarding this, may have them completely removed by the condition in which vegetable remains are frequently found in the coal formations, by the perfect preservation of the most delicately shaped fern leaves, by the upright position of stems, and by other appearances of a similar character. It is also an important objection against the universality of the cover of water, notwithstanding the wide extent of beds of coal, that they are sometimes accompanied with fossil remains of fresh-water shells, from which we are entitled to draw the conclusion, that they must have been deposited in inclosed basins of inland waters.

From the beds of coal found in various situations among _Alpine_ limestone, as well as in other secondary formations, under similar circumstances, we are at liberty to maintain that they are not indebted for their origin to any universal and sudden revolution.

When we proceed to the second division of coal formations, to brown coal, or to _lignite_, the principal difference we discover is, that the change which the vegetables have undergone, having taken place at a time when the chemical power had lost much of its energy, was incomplete; and besides, we observe in the different brown coal formations the same repetition of single beds alternating with other beds of rocks, the mixture of different minerals, and not unfrequently of upright stems. Some appear to be derived from sea plants, and others from fresh-water plants; but the greater proportion from land plants. They, equally with the beds of black coal, give evidence of a new overflow of water, and the water plants themselves, which never thrive at a great depth, and which frequently appear under prodigious beds of rocks, must have experienced such a change. But that change was scarcely of the kind which we understand by a deluge, and the frequent repetition of deluges indicated, according to some, by the repeated beds of coal from the transition to the newest tertiary periods, is hardly credible. It may be maintained, with more certainty, of _brown coal_ than of _black coal_, that they have been formed in land water, and hence in limited and isolated basins of water, since fresh-water animals are their constant attendants.

Although the beds of coal of our secondary formations appear to have originated in a similar way with other mineral formations, and not by violent catastrophes, it is otherwise with a part of those vegetable remains which are met with in alluvial land. Subterranean forests, whose circumference, in some instances, extends about 70 square leagues, partly in a state of good preservation, and partly more or less decomposed, afford satisfactory proof of deluges, and have undoubtedly been covered up with earth by a violent eruption of standing or running water. But these are local effects, similar to what take place in our own day, but on a larger scale.

There are abundant fossil remains of land animals, resembling those of water animals, found in such a state of preservation, that we cannot suppose them to have been brought hither from distant places, and by means of currents. Their appearing in beds of rocks, or generally in aqueous precipitates, proves that the soil they first inhabited, must have been dry land, afterwards overflowed with water.