File:The Quarterly journal of the Geological Society of London (13365780444).jpg

372 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Mar. 27^
Fig. 2. Ground plan.
S Michele
Mineral spnngs.
Tract covered
by tertiary
freshwater
deposit
filled with boiling muddy water, discharging gas ; for the manufac-
turer now utilizes all the hot gas, and
by the addition of water makes gaseous
orifices into mud volcanos. Nor can we
any longer recognize a hot lagone ap-
proaching to the diameter of sixty
braccie, which Targioni gives as the
maximum size ; still less have we a
little island floating in such a hot lake.
The noises and reverberations in the
caverns, which he compared to the beat-
ing of a hundred fulling-mills, were
doubtless much more overpowering for-
merly than now, when the apertures
are so much closed in, and the issue so
regulated. We learn, however, from the
above-mentioned faithful historian two
points of importance in the considera-
tion of these forms of volcanic action :
— 1st. That although the lagoni were
then said to be increasing in number,
one of the orifices, at Monte Cerboli
and another at Castel Nuovo, had ceased
to act in his time. 2ndly. That flames
were said to issue by night *.
That a connection exists between the
Soffioni and the former geological erup-
tive agency of Tuscany is apparent, the
moment we collate the present and the
former phsenomena. The inference is
indeed determined by an appeal to the
very line under consideration (see fig. 2) .
Beginning at the north and by west,
we see at S. Michele a copious outburst
of serpentine and gabbro, and with it
much contortion and rupture of the
contiguous alberese limestone ; and just
at this junction, the hot springs of S.
Michele, celebrated for many ages for
their medicinal virtues, have their issue.
Proceeding thence over undulating
ground, for the most part occupied by
tertiary tuif, we again find at Monte
Cerboli (Mons Cerberus) on the S. and
by E., a like conjunction of similar
eruptive rocks and dislocated strata, and with them the issue of the
before-mentioned hot-springs. Thenceforward to the S. and by E.,

• Targioni Tozzetti quotes Ugolino da Monte Catini's description of the fumes
  

at Castel Nuovo, near to the baths of Bagni a Morbo, and cites his omission of
any allusion to those of Monte Cerboli as an indication that the latter have burnt
out since that time.
Bagm a Blorbo
Mineral springs
a. a. Alberese and niacigno (cretaceous
and eocene).
b. b. Altered alberese and macigno.
c. Gabbro rosso.
d. Thermal springs.