98 M. Brongniart on the Fresh-water Formations of Italy. 
in all its details, at the beautiful cascades of Term. We find, 
at first travertine, or compact fresh-water limestone in the neigh- 
bourhood and lower parts, and near Ilieti, at the confluence of 
the Velino and Nera. This small river precipitates itself in 
the form of a cascade, from a barrier of crystalline concre- 
tionary limestone, formed bv the same means, and on the same 
fundamental soil of compact limestone as at Tivoli. M. d’Hal- 
loy has seen fresh-water shells enveloped in the concretionary 
limestone. 
The fresh-water formation presents, at the place mentioned, 
the banks of Saint Philippo, at some miles to the north-west of 
Hadicofani, on the frontiers of Tuscany, a locality cited in all 
the works on mineralogy, for the application which Dr Vegni 
has made of the property which these hot-springs possess, of de- 
positing a great quantity of very fine and white calcareous mat- 
ter, to the fabrication of very beautiful bas-reliefs. Not only is 
the origin of the fresh-water formation here evident, but this de- 
posit is in so distinct a situation, that this place might serve, so 
to speak, as a model for giving an idea of the formation of hills, 
and even of a great number of calcareous mountains. 
In fact, the springs impregnated with carbonate of lime, issue 
in abundance from the fundamental soil, which is a fine com- 
pact limestone, of a greyish colour, which might be referred to 
the alpine, or even to the transition limestone : they issue towards 
the bottom of a valley hollowed out in this limestone, and they 
have raised in this valley a true hill of white concretionary lime- 
stone, sometimes compact, more frequently crystalline, and ha- 
ving a fibrous structure. This hill of modern formation has 
very steep slopes, which are, however, interrupted by small ter- 
races, and terminated by a rounded platform, on which the baths 
and hamlet of Saint Philippo are built, and where gardens and va- 
rious kinds of culture are established. This limestone formed 
successively, and in contact with the air, has not the compact- 
ness and fineness of grain possessed by that deposited at the bot- 
tom of a lake : it envelopes organic bodies of all sorts, but the 
substance of these bodies is not petrified. 
It may be remarked that this calcareous spring, like that of 
Tivoli, as well as a great number of those in the neighbourhood 
of Naples, in Sicily, &c. ; is upon the limits of volcanic forma- 
