54 Sir R. I. Murcbison on the Vents of Hot Vapour in Tuscany. 



lime, the sulphates of lime, magnesia, and alumina, ^\'ith [boracic 

 and siliceous acids. All of them are charged \vith carbonic acid gas, 

 and one of them with a minute portion of sulphuric acid gas. 



The spot now called Lardarello, where the new establishment 

 has been built, is that portion of the vallej'^ rising from Monte Cerboli 

 and watered l)v the Posera from whence the hot vapours escape by 

 orifices, which, like the mineral springs, mark a line from N. and by 

 AV. to S. and by K. (fig. 1). The sides of this valley consist chiefly 



Fig. 1. Lai'daretlo and the Soffioni seen from Monte Cerboli. Look- 

 ing S. and by E., Lardarello buildings seen one mile off. 



II, a, Alberesc and macigno. /'• Gabbro rosso and ser))entiuc. 



of alberese limestone and schists, with some points of j)rotruding 

 scrpentinous rocks, the lower slopes being partially covered, as far as 

 observation was possible, with younger marls. But whilst these rocks 

 flank the fissure on the E. and W., it is quite open, as before said, to 

 Monte Cerboli and its hot springs on the N. and by W. : it also leads 

 til rough undulating ground to Bagni a IMorbo, about a mile distant 

 to the S. and by E., where hot mineral waters also exist. The present 

 l.igoni are artificially fonued on those points where water and earth 

 are applied to the escapes of the intensely hot vapours. Partially 

 repressing the issue of heat, by throwing on earth and clay, and 

 thus controlling the size of the orifices, human agency forms active 

 mud %olcanos, the number of which and their successive operations 

 are regulated at pleasure. From the limited space in this valley of 

 Lardarello so irrigated and operated upon, various columns of vapour 

 are seen rising to difi'erent altitudes, at different degrees of intensity. 

 This ])erforated ground is in a continually chaotic state from the 

 countless changes it undergoes ; and its outlines are indeed so con- 

 stantly varying by the fonnation of fresh outlets of gas, that the tra- 

 veller who should venture among its mazes without an experienced 

 guide would be exposed to great danger. Even the workmen occasion- 

 ally lose a leg, and sometimes life, when they incautiously tread upon 

 a covering of earth too thhi to prevent their sinking into a hot abyss. 

 Tlie orifice which 1 best examined was jicrfectly circular, about fifteen 

 l)aces in dianutcr, and at the most active moment of ebidlition. Throw- 



