known for the last twenty-five centuries, and in
that time has undergone no material change. Again, in Sicily, similar
interior sea-cliffs are seen, the rubbish at their bases containing the
bones of the hippopotamus and mammoth, proofs of the great change the
climate has undergone since the sea washed those ancient beaches. Italy,
pre-eminently the historic country, in which, within the memory of man,
no material change of configuration has taken place since the
Pleistocene period, very late geologically speaking has experienced
elevations of fifteen hundred feet. The seven hills of Rome are of the
Pliocene, with fluviatile deposits and recent terrestrial shells two
hundred feet above the Tiber. There intervened between the older
Pliocene and the newer a period of enormous length, as is demonstrated
by the accumulated effects taking place in it, and, indeed, the same may
be said of every juxtaposed pair of distinctly marked strata. It
demanded an inconceivable time for beds once horizontal at the bottom of
the sea to be tilted to great inclinations; it required also the
enduring exertion of a prodigious force. Ascent and descent may be
detected in strata of every age: movements sometimes paroxysmal, but
more often of tranquil and secular kind. The coal-bearing strata, by
gradual submergence, attained in South Wales a thickness of 12,000 feet,
and in Nova Scotia, a total thickness of 14,570 feet; the uniformity of
the process of submergence and its slow steadiness is indicated by the
occurrence of erect trees at different levels: seventeen such
repetitions may be counted in a thickness of 4515 feet. The age of the
trees is proved by their size, some being four feet in diameter. Round
them, as they gradually went down with the subsiding soil, calamites
grew at one level after another. In the Sidney coal-field fifty-nine
fossil forests thus occur in superposition.

[Sidenote: Organic proofs of a former high temperature.] Such was the
conclusion forcing itself from considerations connected with inorganic
nature. It received a most emphatic endorsement from the organic world,
for there is an intimate connexion between the existence and well-being
both of plants and animals, and the heat to which they are exposed. Why
is it that the orange and lemon do not grow in New York? What is it that
would inevitably ensue if these exotics were exposed to a cold winter?
What must take place if, in Florida or other of the Southern states