st a
demonstrable fact, that the slow action of streams had hollowed them in
several places into deep chasms nearly two thousand years ago; for the
remains of Roman works of about that age survive, to show that they had
then, as now, to be spanned over by bridges, and that baths had been
erected in their denuded recesses; and yet the craters out of which
these lavas had flowed retain well nigh all their original sharpness of
outline. No wave ever dashed against their symmetrically sloping sides.
Now, I have in no instance seen the argument derivable from this class
of facts fairly met. The supposed mistake of the Canonico Recupero, or
rather of Brydone, who argued that the "lowest of a series of seven
distinct lavas of Aetna, most of them covered by thick intervening beds
of rich earth, must have been fourteen thousand years old," has been
often referred to in the controversy. Brydone or the Canon mistook, it
has been said, beds of brown ashes, each of which might have been
deposited during a single shower, for beds of rich earth, each of which
would have taken centuries to form. The oldest of the series of lava
beds, therefore, instead of being fourteen thousand, might be scarce
fourteen hundred years old. And if Brydone or the Canon were thus
mistaken in their calculations, why may not the modern geologists be
also mistaken in theirs? Now, altogether waiving the question as to
whether the ingenious traveller of eighty-six years ago was or was not
mistaken in his estimate,--for to those acquainted with geologic fact in
general, or more particularly with the elaborate descriptions of Aetna
given during the last thirty years by Elie de Beaumont, Hoffmann, and
Sir Charles Lyell, the facts of Brydone, in their bearing on either the
age of the earth or the age of the mountain, can well be
spared,--waiving, I say, the question whether the traveller was in
reality in mistake, I must be permitted to remark, that the concurrent
testimony of geologists cannot in fairness be placed on the same level
as the testimony of a man who, though accomplished and intelligent, was
not only no geologist, but who observed and described ere geology had
any existence as a science. Further, I must be allowed to add, that
geology _is_ now a science; and that individuals unacquainted with it in
its character as such place themselves in positions greatly more
perilous than they seem to think, when they enter on the field of
argument with men who for