sulphureous exhalations from the lake, the quantity of vegetable matter
generated there and its heat make it the resort of an infinite variety of
insect tribes, and even in the coldest days in winter numbers of flies
may be observed on the vegetables surrounding its banks or on its
floating island's, and a quantity of their larvae may be seen there
sometimes encrusted and entirely destroyed by calcareous matter, which is
likewise often the fate of the insects themselves, as well as of various
species of shell-fish that are found amongst the vegetables, which grow
and are destroyed in the travertine on its banks. Snipes, ducks, and
various water-birds, often visit those lakes, probably attracted by the
temperature and the quantity of food in which they abound; but they
usually confine themselves to the banks, as the carbonic acid disengaged
from the surface would be fatal to them if they ventured to swim upon it
when tranquil. In May, 18--, I fixed a stick on a mass of travertine
covered by the water, and I examined it in the beginning of the April
following for the purpose of determining the nature of the depositions.
The water was lower at this time, yet I had some difficulty, by means of
a sharp-pointed hammer, in breaking the mass which adhered to the bottom
of the stick; it was several inches in thickness. The upper part was a
mixture of light tufa and the leaves of confervae; below this was a
darker and more solid travertine, containing black and decomposed masses
of confervae; in the inferior part the travertine was more solid and of a
grey colour, but with cavities which I have no doubt were produced by the
decomposition of vegetable matter. I have passed many hours, I may say
many days, in studying the phenomena of this wonderful lake; it has
brought many trains of thought into my mind connected with the early
changes of our globe, and I have sometimes reasoned from the forms of
plants and animals preserved in marble in this warm source to the grander
depositions in the secondary rocks, where the zoophytes or coral insects
have worked upon a grand scale, and where palms, and vegetables now