it was a dogma of the
Gaulish Druids that the universe was immortal, but destined to survive
catastrophes both of fire and water. That this doctrine was communicated
to them from the East, with much of their learning, cannot be doubted.
Caesar, it will be remembered, says that they made use of Greek letters
in arithmetical computations.[31]

_Pliny._--This philosopher had no theoretical opinions of his own
concerning changes of the earth's surface; and in this department, as in
others, he restricted himself to the task of a compiler, without
reasoning on the facts stated by him, or attempting to digest them into
regular order. But his enumeration of the new islands which had been
formed in the Mediterranean, and of other convulsions, shows that the
ancients had not been inattentive observers of the changes which had
taken place within the memory of man.

Such, then, appear to have been the opinions entertained before the
Christian era, concerning the past revolutions of our globe. Although no
particular investigations had been made for the express purpose of
interpreting the monuments of ancient changes, they were too obvious to
be entirely disregarded; and the observation of the present course of
nature presented too many proofs of alterations continually in progress
on the earth to allow philosophers to believe that nature was in a state
of rest, or that the surface had remained, and would continue to remain
unaltered. But they had never compared attentively the results of the
destroying and reproductive operations of modern times with those of
remote eras, nor had they ever entertained so much as a conjecture
concerning the comparative antiquity of the human race, or of living
species of animals and plants, with those belonging to former conditions
of the organic world. They had studied the movements and positions of
the heavenly bodies with laborious industry, and made some progress in
investigating the animal, vegetable, and mineral kingdoms; but the
ancient history of the globe was to them a sealed book, and, although
written in characters of the most striking and imposing kind, they were
unconscious even of its existence.

CHAPTER III.

HISTORY OF THE PROGRESS OF GEOLOGY--_continued_.

Arabian writers of the tenth century--Avicenna--Omar--Cosmogony
of the Koran--Kazwini--Early Italian writers--Leonardo da
Vinci--Fracastoro--Controversy as to the real nature of
fossils--Attributed to t