f 
190 TT. S. Hunt on the Chemistry of Natural Waters. 
oxydation of the hydrogen may deposit its sulphur in erates 
d fissures. In other cases, as shown by Dumas, the sulphur 
an ssure; 
ous acid, which afterward absorbing oxygen from the air is com 
id 
the Tuscan suffiozz. 
: 
‘limed in some voleanos, or volatilized with the watery vapor of ; 
§ 31. The action of subterranean heat upon buried strata coh 
taining sulphates and chlorids is then sufficient to explain 
appearance of hydrochloric and sulphurous acids and sulphur, 
even without the intervention of organic matters, which ei 
however, seldom or never wanting ; whether as coal, lignite, 
tion of marsh-gas, is, however, in most cases clearly uncon® 
volcanic action or subterranean heat.  }iceots 
To the decomposition of carbonates in buried strata by sili 
OF €arbonic acid gas which are in many places evolved os ids’ 
and impregnating the infiltrating waters, give TISe nag” 
 ulous Springs. The principal sources of this gas in Earope ay : 
eee en Pee 
tons adjoining voleanos, either active or recently ex 
* See the note to § 22, on kieserite. 
