unknown are preserved with the remains of crocodiles, turtles, and
gigantic extinct animals of the _sauri genus_, and which appear to have
belonged to a period when the whole globe possessed a much higher
temperature. I have, likewise, often been led, from the remarkable
phenomena surrounding me in that spot, to compare the works of man with
those of Nature. The baths, erected there nearly twenty centuries ago,
present only heaps of ruins, and even the bricks of which they were
built, though hardened by fire, are crumbled into dust, whilst the masses
of travertine around it, though formed by a variable source from the most
perishable materials, have hardened by time, and the most perfect remains
of the greatest ruins in the eternal city, such as the triumphal arches
and the Colosaeum, owe their duration to this source. Then, from all we
know, this lake, except in some change in its dimensions, continues
nearly in the same state in which it was described 1,700 years ago by
Pliny, and I have no doubt contains the same kinds of floating islands,
the same plants, and the same insects. During the fifteen years that I
have known it it has appeared precisely identical in these respects, and
yet it has the character of an accidental phenomenon depending upon
subterraneous fire. How marvellous then are those laws by which even the
humblest types of organic existence are preserved though born amidst the
sources of their destruction, and by which a species of immortality is
given to generations floating, as it were, like evanescent bubbles, on a
stream raised from the deepest caverns of the earth, and instantly losing
what may be called its spirit in the atmosphere." These last
observations of the stranger recalled to my recollection some phenomena
which I had observed many years ago, and of which I could then give no
satisfactory explanation. I was shooting in the marshes which surround
the ruins of Gabia, and where there are still remains supposed to be of
the Alexandrine aqueduct; I observed a small insulated hill, apparently
entirely composed of travertine, and from its summit there were