To come to later periods; it has been said, by Volta, as we before observed, that 105 species of the fish found in Monte Bolca, are now the inhabitants of distant seas. Assuredly many of the fish found there still the Mediterranean, as we trust we have proved in its proper place; while, as we formerly remarked. they could not have been transported, hut must have been elevated at once from the bottom of the ocean, by some extensive volcanic operation. This fact, therefore, proves nothing respecting changes of climate.
It has been attempted to argue in the same manner re specting the elephants and similar animals now found buried in the frozen regions of the north, when their living resemblances are confined to hot climates. But this seems chiefly a question, as in the case of plants, respecting spe cies and analogies. It is not decided that the species of these northern animals are the ame as the southern ; in man) instances, the c ntrary is known to he the case; and we have therefore no reason to say that such species could nut have inhabited these regions, or that animals are limit ed to climates by wider analogies. Even where species should prove identical, we know not hut that the habits of animals are, in this respect, convertible; since the dog, the horse, and the fox, for example, are spread over all the climates of the globe; as are many of the migratory birds.
But the state in which an example at least of the ani mal in question was found, renders it certain that the cli mate in which it was buried was also that in which it lived and died. This is the mammoth, already mentioned, as hay in; been found entangled in ice in northern Asia : an ex ample, too, which is not solitary, as far as the present ar gument is concerned. It rests on the authority of Pallas, that a rhinoceros nearly entire was found buried in the earth on the banks of the \Vilui; in a temperature where the earth, at a very small depth beneath the surface, is in a state of perpetual congelation. We need not quote more instances in confirmation of this opinion ; as there can re main no doubt that even these two examples are sufficient to prove that the climate of Siberia, when these animals lived, was the same as it is at present; and that, what ever revolutions may have taken place in the globe, as far, at least, as regards the later fossil remains, these have been revolutions in the species, the habits, or the places of its inhabitants, not of the climate or of the position of the earth's axis.
Thus much respecting the doubtful facts which indi cate changes of climate in the globe; but a few words will be requisite on that supposed change of the earth's axis to which they have been attributed. At present the mo tions of the earth are so regulated, that, in no series of years, could they cause any change in the axis capable of producing any effect on the climate, far less that total change from the present to an equatorial position, which is demanded by the supporters of that opinion. Astro
nomy here leaves the geologist to his own inventions, and it is for him to consider whether he is entitled to regulate the mundane system by such imperfect evidence as his science affords. Having 110 resource, therefore, in that tedious change in the earth's position, which produces the precession of its equinoctial points, he may inquire, 'whether, as has been supposed, the centre of gravity of the whole earth may not have been changed by means of actions which the inventors of this hypothesis have neither ex plained nor applied; or whether the imaginary appulse of a comet may not have produced a sudden and entire al teration of its position. But here we enter on the regions of poetry and imagination. However these speculations may amuse, they do not admit of reasoning. Of those who may find pleasure in them, it is scarcely worth while to ask, whether the facts which these violent suppositions are required to explain, are established; or whether they are not attempting to illustrate doubtful things by things more doubtful. There is much, doubtless, that is possible respecting former conditions of the earth, and concerning which we cannot prove a negative; but these inquiries constitute no part of the present subject, and not a much larger one of rational philosophy.
There is an hypothesis, however, under which such changes, or at least some considerable changes of the axis of the earth, are possible, granting that which the hypo thesis in question implies, viz. a long period of time, and numerous successive revolutions. This is the theory of Dr. Hutton. Taking an extreme case in this theory, we may suppose that the earth was at first a very irregular mass, and that its spheroidal figure was not the conse quence either of an universal state of fluidity, or even of a very considerable one. But in the progress of waste, from the usual powerful causes which still tend to alter the state of the surface, and during other successive revolu tions by which the strata have been broken up and dis placed, it is plain from geometrical considerations, into which we will not here enter, that the present spheroidal form may, after many intermediate vacillations, have been produced. Thus the position of the axis would neces sarily also vary ; and it is only necessary to assume a suffi cient number of such changes, sufficient also in extent, to account for anv change in the position of the globe. We need not dwell on the probabilities of this explanation. It is sufficient if they are consistent with the laws by which the earth is at present governed, and that they involve no impossibilities of any kind.