It is unquestionably possible, for example, that the Black Sea may have been once an inland lake, which has, either from the consequences of gradual waste, or from more sudden and violent causes, found a passage into the Mediterranean. It is even probable that the great plain of Thessaly, as ancient writers inform us, may have been laid dry in the same manner. These, and many similar events, on which geologists have speculated, may have produced currents attended by a distant transportation of alluvial matters, and, of course, of such shells as they might have contained. But such events, whatever other proofs we may have of them, cannot be established by their supposed effects in this respect, as so many other causes may have given to shells the appearance of transportation, and as from the uncertainty already pointed out, which attends the nature and correspondence of species, these cannot be securely traced to distant sources.
But even the instance just alluded to could only have produced alluvial deposits, as the consolidation and eleva tion of rocks are prior to that state of the globe in which they must have taken place. Similar ones, in more an cient times, and in a more ancient state of the globe, might unquestionably have produced corresponding ap pearances in the rocky deposits ; but it seems vain to speculate on such possible events, for purposes so uncer tain and so incapable of proof. It is easy to see, from the example of the Caspian, how a transportation may have been imagined where it never took place. Shells are every where dispersed at great distances from the present seat of this lake, unlike those of the \Volga, or other rivers near which they live, but resembling those of the lake itself. But it is apparent, from a variety of cir cumstances, that the bounds of the Caspian Sea have been contracted; and thus these depositions are accounted for, without transportation by imaginary floods.
The hypothesis of transportation has been also applied to the explanation of such cases as that of Monte Bolca ; hut we have already said enough on that subject, and we need only further observe, that the hypothesis is not wanted, because the facts which it pretends to explain are in some instances not established, and in others may be accounted for on other more obvious principles. The same remarks nearly may be made on its application to the question of climate, so lately discussed. In the more striking cases, or in those of the vegetables of the coal strata, their condition renders a transportation impossible; and the uncertainty of the whole subject is such as to render this hypothesis respecting it superfluous.
It is still necessary to bestow a few words on the ques tion of transportation in the case of the fossil remains of Dalmatia, and of those found in the alluvial soils; although, respecting the latter, the remarks on climate already made have already superseded the necessity of any detailed observations. With respect to the former, they are found
scattered over a great extent of country ; but are more abundant, according to the Abbe Fortis, who has describ ed them, in the islands of Cherso and Osero, where they are imbedded with argillaceous and calcareous matter, mixed with fragments of rock, in chasms or fissures of the strata. These remains are principally the bones of vari ous animals, supposed to be herbivorous, sometimes un known, and very much broken and confused. But that they have been produced or deposited by some general catastrophe which overwhelmed a multitude of animals in one place, or that they were deposited by some deluge, cannot be proved ; while it is much more probable that they have been accumulated where they now are during the lapse of ages, in the manner we formerly hinted, as those probably have been which are now found in the rock of Gibralter.
On the subject of those fossil bones found in alluvial soils, which have been supposed the result of transporta tion, we may add here a few remarks to those already of fered, to prove that the Siberian remains are those of animals that have lived in the climates where they are now found, and that they have not been brought to their present places by transportation from a distant country. The facts are interesting, although further arguments against their transportation should prove superfluous. The extent which they occupy is no less great than remark able, since it exceeds 4000 miles. From Pallas we learn that the bones of the elephant, rhinoceros, and other large animals, have been found in or near every considerable river of northern Asia, from the Tanais to the Anadyr, or nearly from the Black Sea to the Gulf of Kamtschatka. They are, however, chiefly limited to the alluvial plains, being rarely found among the mountains. No torrent or inundation can be conceived capable of producing effects so uniform and extensive; and it therefore follows, as we attempted to show before, that these animals, under dif ferences of species, habits, food, or other circumstances, once inhabited the plains whence they have so long dis appeared. That entire skeletons should have been sub jected to a power so enormous as a torrent capable of extending over so large a tract of country, or that not only these, but the entire carcasses formerly mentioned, shouldhave resisted the effect of such a devastation, is Impossible. That these should have been floated by the sea from more southern latitudes to their present abodes, as is supposed by Pallas, is equally impossible; as, under these circumstances, the skin and muscular parts could not have been preserved ; while the fact formerly noticed, of their occasional entanglement in ice, seems sufficient to set this question at rest for ever.