• But a difficulty yet remains. For though we regard it as probable, that the animals of one continent have removed to the other by the Arctic passages, and allow, that this supposition has been freed from any objection of much force, it is evident that the animals of the northern latitudes only could reach America in the way to which we allude. But it is certain, that there are animals of warm climates, as the lion, the tiger, and the alligator, to be found in the New World; and as those could not pass, either by the north of Europe, or of Asia, because (say the objectors) they could not live there ; it is obvious, if we adhere to the principle that the animals of the New World came originally from the Old, we must account for their migration by some other route than those which have vet been mentioned. The equinoctial animals, it is said, could pass only by a corn immication in the regions of the torrid zone : or, at least, in those regions where the heat is considerable during a great part of the year, and where the general tempe rature is moderate.
In order to obviate the difficulty which has now been stated, it deserves to be remarked, that there are very few animals of the torrid zone to be found in America. This is so much the case, that Buffon has absolutely denied, that any quadruped habituated to a warm cli mate in the Old World exists in the Ncw: hut the asser tion of that distinguished naturalist has not, in this in stance, a sufficient support from an unbiassed view of animated nature, as it appears on the American conti nent. It is unquestionable, however, that the number of animals belonging to the warmer climates in the New World is exceedingly small. Only a few species are to be found there : of course, only a few species have pass ed from the eastern to the western hemisphere. Now, though it is certain that the animals of the torrid zone are peculiar to that region of the earth, and those which are contiguous to it ; yet it is equally certain, that these animals can exist in the more northern latitudes. The infer for creatures, a:, w ell as man, ltrt capable of ac commodating themselves to almost climate. II. therefore, any cause has driven a kW species towarth. the north of Asia, and continued to Operate for any length of time, or has been succeeded by other causes, detaining them in the latter situation, they inay gradually have been accustomed to the less hospitable regions ; and, at length may ha\ e passed from Kamschatka to the American shore, undergoing, either in their pas sage in their way to it, or alter it had taken place, soni:_, of the changes, to which we know, from their appear ance in the Western World, they have been subjected.
If any of the individuals remained for a while in the northern latitudes, they may either halve perished from accidental circumstances, or have been destroyed by tin inhabitants of those regions ; their numbers being small, and their physical strength diminished by the influence of the climate.
There is more ground for this supposition than ap pears at first view. It is extremely probable, that such causes as we have mentioned really operated, and gaNe rise to the effects which we have ascribed to them. We know that the population of the ancient continent advanced from the equatorial regions towards the high er latitudes, and especially towards the north. 11 this be allowed, it is not unreasonable to admit, that, in the progress and multiplication of human beings, some animals of the torrid zone may have been driven before them from their early and more favourable abodes; that these animals may have reached the Asiatic shore, which is nearest to America, passed over to that conti nent, and at length found there a region suited to their natures, where they continued to live, and where they exist at the present day. Those of them which re mained in the northern latitudes of Asia and America, enfeebled by the climate, may have been destroyed by the same cause which forced than thither—the increase and progress of the human species. Hence it is, that their original abodes in the eastern hemisphere, and their corresponding haunts in the western, where they have preserved or partially regained their physical strength, arc the only regions in which they are to be found at present, because in these regions alone they have been able to resist the approaches and the art of man.
If what has been said is not reckoned sufficient to ob viate the difficulty which we have stated, there remains no other solution, as it appears to us, than that the con tinent of Asia was formerly united to the Western World, in the more southern latitudes ; and that the innume•a ble islands in the Pacific Ocean are the higher parts of the land, which completed, above water, the connection between the Old World, and the New. Or, if this hy pothesis likewise is exceptionable, we must suppose that the peninsula of Africa was joined to the eastern hemisphere, in ages unknown to research: and that the islands of St Matthew, St Thomas, and St Helena, toge ther with the Canaries, the Cape Verd islands, and those of the West Indies, are the remains of the union which once existed between the continents on the oppo site sides of the Atlantic. (1)