lohich accompany the Boracic Acid in the Lagoons of Tuscany. 289 



both evolve a gas which possesses a strong odour of petroleum. 

 One of them, the highest by some metres, and the nearest to the 

 centre of the sojffioni, has a temperature of 179°*6 F., and fur- 

 nishes unmistakeable indications of hydrosulphuric acid with 

 acetate of lead ; the other, which is cold, scarcely colours acetate 

 of lead paper : both contain much carbonic acid and an inflam- 

 mable gas*. 



To complete what relates to the fissure of Monte Cerboli, we 

 must add that at the upper limit of the soffioni, in the bed of the 

 Possera, there are the mineral waters of the Bagni a Morbo, 

 acidulous springs, with a temperature of 118°'4 F,, one of which, 

 that of La P«'/«, evolves at once hydrosulphuric and carbonic acids. 

 The presence of these mineral waters and of the bituminous 

 exhalations indicates very distinctly the decrease of intensity 

 in the eruptive phjenomena, in proportion both as we depart 

 from the centre of the soffioni and from the serpentine mass of 

 Monte Cerboli. These peculiarities present a striking resem- 

 blance to the phjenomena which were exhibited to us by the vol- 

 canic masses of Southern Italy. 



From the impossibility of giving here the same details upon, 

 the difl^erent centres of emanations, we shall confine ourselves to 

 citing the localities, and giving a tabular summary of the results 

 of the analyses of the gases. 



Castelnuovo is separated from Larderello by a small ridge ; 

 the fissure which unites its soffioni is directed towards the valley 

 of the Pavone, and is nearly the continuation of that of Monte 

 Cerboli. 



Logo. — This centre of emanations is more complex than the 

 others. The principal fissure is met towards the top by another 

 which intersects it at a considerable angle ; and towards the bot- 

 tom it spreads out into a lake from which numerous soffioni 

 escape. 



Monte Rotondo and Sasso. — These two centres of emanations 

 are united by a single fissure, which principally traverses the 

 micaceous grits or macigno, and has modified them in a thousand 

 ways. 



At Serrazano and Lustignano, the strata traversed and modified 

 consist principally of alberesc. In these two localities, however, 

 we confined ourselves to some short experiments, which gave us 

 exactly the same results as for the other lagoons. 



* The following is the analysis of the gas collected at the hot emana- 

 tions : Ilydrosulphm-ic acid traces 



Carbonic acid 811 



Oxygen 2'9 



Nitrogen 133 



I lydrogen 1 '3 



Protocarbonatcd hydrogen 1"4 



Phil, Mag, S. 4. Vol. 10. No. 107. Oct. 1858. U 



