have any idea as to the cause of the large quantity of carbonic acid
which you have been so good as to inform us exists in most of the waters
in this country?" The stranger replied, "I certainly have formed an
opinion on this subject, which I willingly state to you. It can, I
think, be scarcely doubted that there is a source of volcanic fire at no
great distance from the surface in the whole of southern Italy; and, this
fire acting upon the calcareous rocks of which the Apennines are
composed, must constantly detach from them carbonic acid, which rising to
the sources of the springs, deposited from the waters of the atmosphere,
must give them their impregnation and enable them to dissolve calcareous
matter. I need not dwell upon Etna, Vesuvius, or the Lipari Islands to
prove that volcanic fires are still in existence; and there can be no
doubt that in earlier periods almost the whole of Italy was ravaged by
them; oven Rome itself, the eternal city, rests upon the craters of
extinct volcanoes; and I imagine that the traditional and fabulous record
of the destruction made by the conflagration of Phaeton in the chariot of
the sun and his falling into the Po had reference to a great and
tremendous igneous volcanic eruption, which extended over Italy and
ceased only near the Po at the foot of the Alps. Be this as it may, the
sources of carbonic acid are numerous, not merely in the Neapolitan, but
likewise in the Roman and Tuscan states. The most magnificent waterfall
in Europe, that of the Velino, near Terni, is partly fed by a stream
containing calcareous matter dissolved by carbonic acid, and it deposits
marble, which crystallises even in the midst of its thundering descent
and foam in the bed in which it falls. The Anio or Teverone, which
almost approaches in beauty to the Velino in the number and variety of
its falls and cascatelle, is likewise a calcareous water; and there is
still a more remarkable one which empties itself into this river below
Tivoli, and which you have probably seen in your excursions in the
campagna of Rome, called the lacus Albula or the lake of the Solfatara."