_Increase of rein-deer imported into Iceland._--As an example of the
rapidity with which a large tract may become peopled by the offspring of
a single pair of quadrupeds, it may be mentioned that in the year 1773
thirteen rein-deer were exported from Norway, only three of which
reached Iceland. These were turned loose into the mountains of
Guldbringe Syssel, where they multiplied so greatly, in the course of
forty years, that it was not uncommon to meet with herds, consisting of
from forty to one hundred, in various districts.

The rein-deer, observes a modern writer, is in Lapland a loser by his
connexion with man, but Iceland will be this creature's paradise. There
is, in the interior, a tract which Sir. G. Mackenzie computes at not
less than forty thousand square miles, without a single human
habitation, and almost entirely unknown to the natives themselves. There
are no wolves: the Icelanders will keep out the bears; and the
reindeer, being almost unmolested by man, will have no enemy whatever,
unless it has brought with it its own tormenting gad-fly.[982]

Besides the quadrupeds before enumerated, our domestic fowls have also
succeeded in the West Indies and America, where they have the common
fowl, the goose, the duck, the peacock, the pigeon, and the guinea-fowl.
As these were often taken suddenly from the temperate to very hot
regions, they were not reared at first without much difficulty: but
after a few generations, they became familiarized to the climate, which,
in many cases, approached much nearer than that of Europe to the
temperature of their original native countries.

The fact of so many millions of wild and tame individuals of our
domestic species, almost all of them the largest quadrupeds and birds,
having been propagated throughout the new continent within the short
period that has elapsed since the discovery of America, while no
appreciable improvement can have been made in the productive powers of
that vast continent, affords abundant evidence of the extraordinary
changes which accompany the diffusion and progressive advancement of the
human race over the globe. That it should have remained for us to
witness such mighty revolutions is a proof, even if there was no other
evidence, that the entrance of man into the planet is, comparatively
speaking, of extremely modern date, and that the effects of his agency
are only beginning to be felt.

_Population which the globe is capable of supporting._--A