lated at certain spots, could hardly
boast of more large quadrupeds than Southern Africa does at
present. If we speculate on the condition of the vegetation during
those epochs, we are at least bound so far to consider existing
analogies, as not to urge as absolutely necessary a luxuriant
vegetation, when we see a state of things so totally different at
the Cape of Good Hope.

We know that the extreme regions of North America many degrees
beyond the limit where the ground at the depth of a few feet
remains perpetually congealed, are covered by forests of large and
tall trees. (5/9. See "Zoological Remarks to Captain Back's
Expedition" by Dr. Richardson. He says, "The subsoil north of
latitude 56 degrees is perpetually frozen, the thaw on the coast
not penetrating above three feet, and at Bear Lake, in latitude 64
degrees, not more than twenty inches. The frozen substratum does
not of itself destroy vegetation, for forests flourish on the
surface, at a distance from the coast.") In a like manner, in
Siberia, we have woods of birch, fir, aspen, and larch, growing in
a latitude (64 degrees) where the mean temperature of the air falls
below the freezing point, and where the earth is so completely
frozen, that the carcass of an animal embedded in it is perfectly
preserved. (5/10. See Humboldt "Fragmens Asiatiques" page 386:
Barton's "Geography of Plants"; and Malte Brun. In the latter work
it is said that the limit of the growth of trees in Siberia may be
drawn under the parallel of 70 degrees.) With these facts we must
grant, as far as QUANTITY ALONE of vegetation is concerned, that
the great quadrupeds of the later tertiary epochs might, in most
parts of Northern Europe and Asia, have lived on the spots where
their remains are now found. I do not here speak of the KIND of
vegetation necessary for their support; because, as there is
evidence of physical changes, and as the animals have become
extinct, so may we suppose that the species of plants have likewise
been changed.

These remarks, I may be permitted to add, directly bear on the case
of the Siberian animals preserved in ice. The firm conviction of
the necessity of a vegetation possessing a character of tropical
luxuriance, to support such large animals, and the impossibility of
reconciling this with the proximity of perpetual congelation, was
one chief cause of the several theories of sudden revolutions of
climate, and of overwhelming catastrophes, which were inv