413. The inhabitants of the globe, then, like all the other parts of it, are subject to change. It is not only the individual that perishes, but whole _species_, and even perhaps _genera_, are extinguished. It is not unnatural to consider some part of this change as the operation of man. The extension of his power would necessary subvert the balance that had before been established between the inhabitants of the earth, and the means of their subsistence. Some of the larger and fiercer animals might indeed dispute with him, for a long time, the empire of the globe; and it may have required the arm of a Hercules to subdue the monsters which lurked in the caves of Bayreuth, or roamed on the banks of the Ohio. But these, with others of the same character, were at length exterminated: the more innocent species fled to a distance from man; and being forced to retire into the most inaccessible parts, where their food was scanty, and their migration checked, they may have degenerated from, the size and strength of their ancestors, and some species may have been entirely extinguished. But besides this, a change in the animal kingdom seems to be a part of the order of nature, and is visible in instances to which human power cannot have extended. If we look to the most ancient inhabitants of the globe, of which the remains are preserved in the strata themselves, we find in the shells and corals of a former world hardly any that resemble exactly those which exist in the present. The species, except in a few instances, ate the same, but subject to great varieties. The vegetable impressions on slate, and other argillaceous stones, can seldom be exactly recognised; and even the insects included in amber are different from those of the countries in which the amber is found. 414. Supposing, then, the changes which have taken place in the qualities and habits of the animal creation, to be as great as those in their structure and external form, we can have no reason to wonder if it should appear that some have formerly dwelt in countries from which the similar races are now entirely banished. The power of living in a different climate, of enduring greater degrees of cold or of heat, or of subsisting on different kinds of food, may very well have accompanied the other changes. Though one species of elephant may now be confined to the southern parts of Asia, another may have been able to endure the severer climates of the north; and the same may be true of the buffalo or the rhinoceros. In all this no physical impossibility is involved; though whether it is a probable solution of the difficulty concerning the origin of these animal remains, can only be judged of from other circumstances. 415. If we consider attentively the facts that respect the Siberian fossil bones, there will appear insurmountable objections to every theory that supposes them to be exotic, and to have been brought into their present situation from a distant country.