258 Notice of Active and Extinct Volcanos. 



ous schist, and reposes in this place upon the ichthyolite lime 

 stone. — Bevalacque-Lazise, page 29 et 36." 



Monte Cimini, Viterbo, and other places on the road to 

 Rome, present traces of volcanic action, but not in every in- 

 stance of an unequivocal character. A small lake near Vi- 

 terbo, emits a sulphureous odour, and the water is agitated 

 by air bubbles. The lake Vico resembles a crater, and was 

 said by the ancients to have been formed by the sinking of 

 the ground. The lake Bolseno resembles an ancient crater, 

 but its circumference is twenty miles, which is greater than 

 that of any known volcano.* The lagunes of Tuscany evolve 

 sulphureous vapours and gases, and the boracic acid is sub- 

 limed alike from the lagunes of Tuscany and from the crater 

 of the island of Volcano. 



" The lagunes in question are represented as being little cra- 

 tershaped cavities formed on the surface of the ground, by the 

 continual escape of sulphuretted hydrogen gas from fissures in 

 the rock. These cavities, according to Prystanowski, (a German, 

 who has published the most modern account of this phenomenon,) 

 are at the bottom of a valley, and are therefore often filled with 

 water, either by the rain, or by the overflowings of an adjoining 

 brook. 



" This water is raised to a boiling temperature by the passage 

 of the heated gas through it, and hence it is that the lagunes gen- 

 erally emit a lofty column of steam, which first arrests the trav- 

 eller's attention, and has consequently led to the adoption of the 

 name Fumacchie, by which the lagunes are often designated. — 

 The sulphuretted hydrogen carries up with it in a gaseous state 

 some boracic acid, but this is condensed by the water, and is found 

 amongst the mud, when the pool has dried up in consequence of 

 the evaporation from it exceeding the supply from without. 



" The lagunes are situated a few miles to the S. W. of Volterra, 

 near Monte Rotundo, and near Monte Cerboli, the rock, from 

 whence the vapor issues is calcareous." 



Rome. — It was a favorite idea with Breislac, that " Rome 

 itself occupied the site of a volcano, having been erected on 

 the tottering edge of a crater." Professor Daubeny thinks 

 that however well suited this idea may be " to point an an- 

 tithesis, or to illustrate the vanity of human pretensions, it 



* Kirauea in Owyhee, (Hawaii,) is ten miles in circumference 



