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. 



e. Lagoni or Sofl5oni. 



