Of true Beavers there is only one species--unless the beaver of the Old World be different from the well-known animal of the American continent. This is a question which has been much debated among naturalists; and certainly the difference which is known to exist between the habits of the two animals would seem to prove them distinct. The European beaver is generally supposed to lead a solitary life--burrowing in the banks of rivers as otters do; but this supposition is evidently erroneous: or, rather, we should say, its solitary habit is not its normal or original condition, but has been produced by circumstances. It is probable that if European beavers were left to themselves, in a situation remote from the presence of man, they would build dams, and dwell together in colonies, just as the American beavers do. In fact, such colonies have actually existed in some parts of Europe and Asia; and no doubt exist at the present hour. One has even been found on the small river Nutha, in a lonely canton of the Magdeburg district, near the Elbe. Moreover, it is well-known that the American beavers, when much hunted and persecuted (as they are certain to be whenever the settlements approach their territory) forsake their gregarious habit; and betake themselves to the "solitary system;" just as their European cousins have done. Did this constitute the only difference between the beavers of the Old and New Worlds, we might regard them as one and the same; but there are other and still more important points of distinction--reaching even to their anatomical structure--which seem to prove them distinct species. The probability is in favour of this view: since there is perhaps no indigenous quadruped of the one continent exactly identical with its synonymous species of the other; excepting the polar bears, and a few other kinds--whose arctic range leads them, as it were, all round the earth. The written natural history of the beaver is usually that of the American species; not that this differs materially from his European congener, but simply because it has been more extensively and accurately observed. Its valuable fur has long rendered it an object of the chase; and for fifty years it has been hunted _a l'outrance_, and, in fact, exterminated from a wide domain of more than a million of square miles. Formerly, its range extended from the Gulf of Mexico almost to the shores of the Arctic Sea, and latitudinally from ocean to ocean. At present, it is not found in the territory of the United States proper, except in remote and solitary situations, among the mountains, or in some tracts still unsettled. Even where found in these places, its mode of life approximates more to that of the European species; that is, it burrows instead of builds. The beaver has been long reputed as the most sagacious of quadrupeds. True it is, that the capacity of cutting down trees--often a foot or more in diameter--floating or rafting these trees