rhinoceroses is certainly one of the most wonderful facts in geology;
but independently of the imagined difficulty of supplying them with
food from the adjoining countries, the whole case is not, I think, so
perplexing as it has generally been considered. The plains of Siberia,
like those of the Pampas, appear to have been formed under the sea,
into which rivers brought down the bodies of many animals; of the
greater number of these, only the skeletons have been preserved, but of
others the perfect carcass. Now, it is known that in the shallow sea
on the Arctic coast of America the bottom freezes, [19] and does not
thaw in spring so soon as the surface of the land, moreover at greater
depths, where the bottom of the sea does not freeze the mud a few feet
beneath the top layer might remain even in summer below 32 degs., as in
the case on the land with the soil at the depth of a few feet. At
still greater depths, the temperature of the mud and water would
probably not be low enough to preserve the flesh; and hence, carcasses
drifted beyond the shallow parts near an Arctic coast, would have only
their skeletons preserved: now in the extreme northern parts of Siberia
bones are infinitely numerous, so that even islets are said to be
almost composed of them; [20] and those islets lie no less than ten
degrees of latitude north of the place where Pallas found the frozen
rhinoceros. On the other hand, a carcass washed by a flood into a
shallow part of the Arctic Sea, would be preserved for an indefinite
period, if it were soon afterwards covered with mud sufficiently thick
to prevent the heat of the summer-water penetrating to it; and if, when
the sea-bottom was upraised into land, the covering was sufficiently
thick to prevent the heat of the summer air and sun thawing and
corrupting it.
Recapitulation.--I will recapitulate the principal facts with regard to
the climate, ice-action, and organic productions of the southern
hemisphere, transposing the places in imagination to Europe, with which
we are so much better acquainted. Then, near Lisbon, the commonest
sea-shells, namely, three species of Oliva, a Voluta, and a Terebra,
would have a tropical character. In the southern provinces of France,
magnificent forests, intwined by arborescent grasses and with the trees
loaded with parasitical plants, would hide the face of the land. The
puma and the jaguar would haunt the Pyrenees. In the latitude of Mont
Blanc, but on an island as far westward as Central North America,
tree-ferns and parasitical Orchideae would thrive amidst the thick
woods. Even as far north as central Denmark, humming-birds would be
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