Part 25

The appearance of what are called fresh water shells, in alternate beds with marine animals, being sometimes observed in newer flœtz rocks in great abundance, seems to indicate a reiterated retreat and return of the sea. But however meritorious the labours of naturalists, through whom attention has been directed to the subject, may be in other respects, we are nevertheless disposed to entertain doubts concerning their conclusions. In our own seas and ponds upon the coasts, we observe the same testaceous animals growing equally well in salt water, and in water nearly fresh; and, again, fresh water animals living in salt water[402]. By artificial means the inhabitants of the sea may be changed into inhabitants of fresh water; as fresh-water animals are, in their turn, converted into marine animals, so that, to decide concerning the proper element of each individual species is often matter of difficulty. Therefore, other circumstances besides that of containing salt must be taken into account. The occasional plenty, scarcity, or absolute want of food; the soil being sometimes sandy, slimy, or rocky; the depth, extent, agitation or tranquillity of the water; and, finally, the quality of the air contained in it, may be as instrumental in determining the habitation of these animals, as the materials which the water holds in solution. An excellent observer has indeed very lately shewn in a treatise, which supports the idea of fresh-water formations, that we possess no unerring character for distinguishing sea shell-fish from those of fresh water; but admitted, notwithstanding the transition above stated, we can draw a line of distinction between them, we must not forget that this investigation is neither regarding sea shell-fish now existing, nor of our present waters. We indeed draw our conclusion, and not without reason, from similar conformation, similar modes of existence. But one of two things must be; either that the shell-fish, whose remains are found in beds of rocks, lived in the water out of which these beds were precipitated, or the water in which they lived, was dislodged by other water containing the materials of the precipitations. In the first and more generally admitted case, the water was so different from the present water, whether salt or fresh, that we cannot infer from the inhabitants of the latter any thing concerning the inhabitants of the former; but we can confidently maintain, that a greater resemblance prevails between our sea and land water, than between either the one or the other, and that fluid which was inhabited by the shell-fish. In other respects, there remains no other difference between fresh and salt water formations, but that the bottom upon which the former is placed once contained land water; a fact worthy of observation: but the notion of enclosed basins, and of isolated formations originating in them, the way in which fresh water formations are supposed to have taken place, remained a long time unsatisfactory. Finally, we may be permitted to ask, upon what grounds they considered themselves entitled to ascribe to the former sea the continual possession of a portion of salt, while the salt precipitates appear only at particular intervals, and after long interruptions? If the sea occasionally contained a great, and sometimes a very small, quantity of salt, it might equally be at times altogether without it. And yet it deserves to be remembered, that the beds of rock, to which the salt formations are most nearly related, contain no petrifactions; that, therefore, the so-called marine animals are wanting in those periods during which we have any direct evidence of the presence of salt water.

There is, however, a geognostic fact, which, in preference to all others, has been cited in evidence of violent revolutions and deluges, that is, the appearance of conglomerates or of reproduced kinds of stone. Indeed, there might still be a wide field for investigation here, and more than one formation, which now passes for sandstone, might be acknowledged as an original and chemical production; without having occasion to go so far as Mr Gerhard does with greywacke,--that is, to consider them as immediate precipitates from the atmosphere. But still conglomerates sufficiently genuine, will remain from the transition period through all the subsequent formations, to serve as acknowledged monuments of destruction, as well as of the renovation of what was destroyed. These are the Codices rescripti, in the archives of the Earth, out of which, the antiquarian will one day decipher the almost obliterated traces of her former condition, as well as the history of her changes. Though these conglomerates deviate so much in their nature, and in the character of their origin, from chemical productions, they have yet among themselves this remarkable and common characteristic, that, with few exceptions, the older are much less varied in character, and more extensive in distribution, than the newer, and that, at length, the newest conglomerates become mere local appearances. But, in reference to the main question which engages our attention, we may conjecture that the beds of rocks from which the sea had never retreated, might be assailed by its floods and currents, and shattered to pieces, as happens even in our own time, and the fragments be again reunited into solid rocks, by means of the still remaining dissolved matter in the water. But of many conglomerates it is evident that they have been deposited on the dry land, in the same way as our gravels. Jupiter, who took counsel with himself, whether he would destroy the sinful world with fire or water, and at length decided for water[403], may not be so justly considered the author of these appearances, as Saturn, who devoured his children. Or, to be less metaphorical in our language, it may perhaps have been with the origin of conglomerates, as it is in our own day with the origin of fragments of rock and boulders, in which the rock being fractured in various places by the alternations of heat and cold, by the influence of air and atmospheric water, falls into pieces of greater or smaller magnitude, which are carried forward by the water, and gradually rounded in their progress, so that they assume a more perfectly globular shape the farther they are removed from their original situation. Therefore, as regards the foregoing enquiry, it is not an unimportant circumstance, that the long but continual rolling of the boulders during their rounding, appears to be much more efficacious than a rapid and violent impetus, and that, in this case, as in many other geognostic appearances, time rather than force is to be taken into account. Another circumstance, perhaps, corresponds with this, that the change produced by the weather, not only by the first disunion, but also by the progressive disintegration of the rocks, by the blunting of the edges and corners, by the diminution of the fragments, and generally in the origin of the boulders and fragments of rocks of every description, has just as much influence as the mechanical operation of the water; and that a great part of the land called Alluvial, generally owes its existence to this cause[404]. But if, upon farther consideration, the conglomerates appear to derive their origin in a similar way with rolled masses of gravel, they afford evidence, nevertheless, of the elevated station of the water in the neighbourhood, from which they had been before removed; for their conglomeration could take place only under water; and, with few exceptions, they occupy an incomparably greater elevation than any of the coal formations, or any of the beds of rocks which enclose the remains of land animals.

Geognosy certainly contains many facts, which cannot be explained, but by a change from dry land to the bottom of the sea, although our knowledge of them is still so imperfect, that we cannot hazard a probable conjecture respecting the numbers of these changes, whether they commence at the same or at different periods in the various quarters of the world, and whether they are local or universal. These changes appear neither sudden nor violent, such as we consider revolutions of the earth, but at all times proceed with silent and regular steps, and depend upon similar causes, concealed it is true from us, such as the universal retreat of the waters from their original height to the present bed of the ocean. We do not belong to those geologists who divert the world from its axis for the purpose of explaining the inequalities of its surface, at whose command the Earth sometimes opens her bosom to engulf the sea, and at other times the floodgates of Heaven are lifted up to pour down another ocean. He who reflects on the devastation caused by earthquakes, inundations and the fall of mountains, even though they are merely local appearances confined to particular quarters, cannot help putting the question to himself, how the order, regularity and connection exhibited by strata of rocks, could in any measure exist, if the same or similar accidents had happened throughout the whole world, and if mechanical power had operated with such energy, and to such an extent? All our knowledge of the structure of the earth, and of the existence of its inhabitants, declares rather a quiet uninterrupted and continually progressive advancement in its formation and development.

In the lapse of geological epochs, we observe a gradation of rock formations following one another, in which the latter, however remotely connected, still appear sufficiently similar to the earlier to indicate a common origin, till they at length terminate in simple formations, resembling those which are presently taking place. When the precipitates were exhausted, and the structure was completed, nay, even earlier, its destruction commenced; not that violent destruction by which lofty mountains are torn asunder and levelled, no uproar of nature, no gigantic struggle of the elements, such as we commonly conceive, but a decomposition of the strata of rocks to a greater or less depth, caused partly by chemical, partly by mechanical, but slow operating powers, what they wanted in intensity being compensated by the endurance of their operation. According to the common law of nature, deficiency of power is supplied by duration of time; for, of all the oracles which have been consulted concerning the formation of the earth, there is no one which can make such important revelations to us as the oracle of the age of mountains. These operations at the earth’s surface generally appear to have produced its present figure, and to have designed it for the habitation of numerous organic beings. This appears as early as a suitable element occurred; first, in water, then in land animals; and, like the formation of rocks, we observe a regular succession of organic formations, the later always descending from the earlier, down to the present inhabitants of the earth, and to the last created being who was to exercise dominion over them. But here occurs this important distinction: the organic world with youthful vigour renews itself daily, and decomposes its materials only to reunite them by fresh combinations in uninterrupted succession; while the powers of the inorganic world appear almost extinguished. Though this course of nature is manifest to our own observation, her resources and progress are, on the contrary, more concealed; and we can hardly lift the veil which conceals her, unless we follow Bacon’s advice, Turn back from rash theories, and follow observation and experience.

We have hitherto endeavoured to shew that incontrovertible geognostic facts indicate an alternate rising and falling of the water which covered the earth’s surface, but that they were not of a kind to justify the notion of violent revolutions, or of sudden and universal eruptions of the sea; and that, therefore, such deluges as the Mosaic deluge, recorded in the traditions of nations, were not revolutions of this description. If, according to the supposition of Cuvier, the earth’s surface inhabited at the commencement of the latter deluge has become the present bed of the sea, and the former bed of the sea has become the present dry land, then, according to the present state of geography, _though only conjectural_, we should be able to point out such portions of the earth as were overwhelmed by the catastrophe; and yet we have never heard that any one has hazarded such an experiment. In the constitution of the present habitable globe, we find no proofs remaining of such a revolution.

Among these revolutions of nature, we never reckon common inundations, such as take place at present from water overflowing its boundaries, though these also may produce devastation whose effects remain visible for an hundred years. But, in mountainous districts, another kind of aqueous eruption makes its appearance, and may be classed along with the traditions of a deluge. We very frequently, for instance, observe the valleys of high mountains forming a range of basins separated from one another by shorter or longer defiles, and opening through the last defile into a wider valley, or a marsh. The shape of these basins, or cauldrons, commonly lying above one another like so many stories, and the level surface of their water, leave no doubt of their being once enclosed lakes which were formerly blocked up by the barriers of the defiles, and which flowed towards the level country, as soon as the defiles were broken down by the waters. If no kind of historical monuments in the west of Europe bears evidence of those events, which, at least on a small scale, occur in our own times, this intimates that it was inhabited, not by an original population, but by a foreign or modern race of people; whereas those revolutions extended to remote antiquity. The numerous masses of rock found on both sides of the Alps to the height of 4000 feet, as well as in the plains of the north of Europe, at a great distance from their original position, and concerning whose coming hither so much light has lately been thrown by Messrs Buch and Escher, are a very probable proof of these debacles; while every circumstance renders it evident that these blocks were swept along by the currents thus created, to the place where they are now found. The Greek writers have also preserved accounts of such revolutions, which, although not unquestionably authenticated, are yet stamped with the impress of historical testimony. Herodotus has the following passages directly relative to the country where the Greeks place their second or Deucalionic deluge. “Thessaly must formerly have been an inland sea, surrounded by high mountains. On the east it was bounded by Pelios and Ossa, whose bases were united; on the north by Olympus; on the west by Pindus; and on the south by Othrys. Thessaly lay in the midst of these mountains in the form of a basin, into which, in conjunction with other copious streams, the five well-known rivers, the Peneus, the Apidanus, the Orochomenus, the Enipeus, and the Pamisos, emptied themselves. These rivers, which are collected in their basin from the mountains which encompass Thessaly, after their junction under the name of Peneus, in which they lose their former appellation, open towards the sea through a narrow valley. According to tradition, this valley and opening did not formerly exist; so that the rivers and the Lake Brebeis, which did not formerly bear these names, having their confluence in this place, rendered the whole of Thessaly an inland sea. The Thessalians affirm that Neptune opened the valley for the passage of the river Peneus, and they may perhaps be right. If we consider Neptune the author of earthquakes, and consider the violent concussion of the mountains caused by them as the work of this deity, we must, upon surveying these regions, confess that they owe their present shape to him; for the separation of every mountain appears to me to have been produced by some violent commotion of the earth.” Strabo makes mention of this tradition, which he thought worthy of belief, and accounts for the origin of the Vale of Tempe, which is the bed of the river Peneus, and likewise for the separation of Ossa from Olympus, by means of an earthquake[405]. In making this remark, we perceive that our theories which allow that earthquakes are to operate in forming the surface of the earth, have not even the merit of novelty. According to the last writer, similar eruptions of water must have originated in the lake Copais in Bœotia[406], in the lakes Bistonis and Aphnetis, in Thrace, and have been accompanied with huge devastation[407]. Diodorus Siculus[408] remembered a Samothracian tradition, according to which the Euxine Sea was once shut up on all sides. It afterwards burst through its mighty mound of _kyanischen_ rocks to the Hellespont, and inundated a great part of the coast of Asia, as well as Samothracia itself. An objection started to the possibility of such an event is, that, from the observations of Olivier and General Andreossy, the shores of the Black Sea are, in most places, lower than those of the Bosphorus; and that its waters, therefore, even if they were considerably higher than they are at present, would more readily overflow the former than the latter. But since every rock exposed for such a length of time is daily crumbling down, it is a question, whether the shore of the Black Sea has undergone any alteration since that period; and we know that the eruptions took their direction, not so much from the low situation of the barrier, as from the nature of the rock of which it was constructed, being influenced by the weather, and from the rock itself being rent asunder. Be that as it may, the words with which Diodorus commences his narrative are remarkable, when he says, the Samothracian deluge happened earlier than those of other nations. It at least so far preceded others, that, in the estimation of the Greek historian, independent of the deluges of Ogyges and Deucalion, similar natural occurrences more or less authenticated were received as historical facts.

Finally, the effects produced by the bursting of lakes or debacles do not appear to be out of proportion to the devastation mentioned by the traditions of nations. To abide by our former example, floods which could carry along with them masses of rock of 50,000 cubic feet, were in a situation to bury a whole people; and the few individuals who might be preserved would undoubtedly have handed down the memory of such an event to remote posterity. Other deluges may have arisen from other causes, at a time when, as is shewn by numerous vestiges, lakes and rivers had a much greater elevation than at present; and, therefore, every overflowing of them must have produced greater and more extensive ravages.

From these last local eruptions of water, that is, from single limited districts, arose the mechanical precipitates known under the denomination of Alluvial Soil. Their situation, as the uppermost covering of the earth, as well as their origin, which takes place beneath our own observation, furnishes evidence of their being the most recent mineral formations; and it follows from their nature and connection that they were not produced by chemical means, but removed by the mechanical force of water. Since they, among other things, contain prostrate forests, and abundant remains of land animals, we conclude that they did not originate in the bed of the sea, but were floated and deposited upon the dry land by an overflow of land water. How is it conceivable that these precipitates have been covered by the ocean, since their deposition, and have, by means of an opposite change, become the dry land they are at present; and yet it must have been so, if they are to be considered as intimations of the Mosaic deluge.

The view now given, which is that of Henger in his Beiträge, is also advocated by other naturalists, and has lately been brought forward in an interesting manner in the Edinburgh Philosophical Journal[409]. We have been frequently requested to give the two views, in regard to the universal deluge, namely, that which maintains that it is proved by an appeal to the phenomena of the mineral kingdom; the other, which affirms that that great event has left no traces of its existence on the surface or in the interior of the earth. M. Cuvier’s Essay, and Professor Buckland’s Reliquiæ, are the best authorities for the first opinion; while numerous writers have advocated the second.

NOTE, p. 244.

ON THE ACTION OF RUNNING WATERS.

A very great degree of power has been attributed to the waters which move at the surface of the earth, or in its interior. Many geologists have advanced the opinion, that they have scooped out the channels and even the valleys in which they flow, and formed the cliffs whose feet they wash; and many philosophers, naturalists and even geologists, still support this opinion, not only in some of its applications, but even in its whole extent.

In order to appreciate it, it is sufficient to observe with care the different modes of action of water set in motion by different causes, and the changes which it has operated upon the rocks and deposits upon which it has acted, from the most remote times to which history may reach.

We must, in the first place, successively examine the different sorts of action of the principal masses of water which are in motion at the surface of the earth, that is to say, the action of torrents, of rivers, of currents of the sea, or of great lakes, and that of waves.

We shall afterwards see what consequences are to be deduced from these observations.

1. _Action of Torrents._

_Torrents_ have a true degrading and _scooping_ action upon the earth’s surface, but, by the necessary consequence of the sense which we attach to the word, this action cannot be exercised upon spaces of great extent, for a torrent is a water-course which has a great declivity. Now, on account of the little height which the most elevated summits of the globe have in comparison with the extent of its surface, this action cannot be very extensive; it can only, therefore, produce short and narrow ravines. This action, as all who have visited high mountain chains may have seen, is only often local and instantaneous; it presents no remarkable effect but upon the heaps of debris which cover the declivities of the mountains, and on broken rocks, partially disintegrated by other causes, and lastly on moveable deposits. The results of this action contribute to confine it within narrower limits still, by heaping up at the mouths of torrents in the valleys or plains, the debris carried down by these torrents. The elevation of the soil, which necessarily follows from the accumulation of these debris, diminishes with the declivity, the rapidity, and consequently the power of these water-courses.