ture, the
introductory and concluding passages of the twelfth chapter of his
"Meteorics" are certainly very remarkable. In the first sentence he
says, "The distribution of land and sea in particular regions does not
endure throughout all time, but it becomes sea in those parts where it
was land, and again it becomes land where it was sea: and there is
reason for thinking that these changes take place according to a certain
system, and within a certain period." The concluding observation is as
follows:--"As time never fails, and the universe is eternal, neither the
Tanais, nor the Nile, can have flowed forever. The places where they
rise were once dry, and there is a limit to their operations; but there
is none to time. So also of all other rivers; they spring up, and they
perish; and the sea also continually deserts some lands and invades
others. The same tracts, therefore, of the earth are not, some always
sea, and others always continents, but every thing changes in the course
of time."

It seems, then, that the Greeks had not only derived from preceding
nations, but had also, in some slight degree, deduced from their own
observations, the theory of periodical revolutions in the inorganic
world: there is, however, no ground for imagining that they contemplated
former changes in the races of animals and plants. Even the fact that
marine remains were inclosed in solid rocks, although observed by some,
and even made the groundwork of geological speculation, never stimulated
the industry or guided the inquiries of naturalists. It is not
impossible that the theory of equivocal generation might have engendered
some indifference on this subject, and that a belief in the spontaneous
production of living beings from the earth or corrupt matter, might have
caused the organic world to appear so unstable and fluctuating, that
phenomena indicative of former changes would not awaken intense
curiosity. The Egyptians, it is true, had taught, and the Stoics had
repeated, that the earth had once given birth to some monstrous animals,
which existed no longer; but the prevailing opinion seems to have been,
that after each great catastrophe the same species of animals were
created over again. This tenet is implied in a passage of Seneca, where,
speaking of a future deluge, he says, "Every animal shall be generated
anew, and man free from guilt shall be given to the earth."[24]

An old Arabian version of the doctrine of the successive rev