294 



DYNAMICAL GEOLOGY. 



out, which becomes hydrochloric acid as it leaves the liquid lava, and is evidence, as has 

 been stated, that sea watei- aids in the action of that volcano. 



Through the sulphurous acid (SO2), sulphur and various sulphates are made; e.g., 

 alums by combination of sulphuric acid (SO3) with alumina and potash or soda ; and 



258-266. 



262 



258 



259 



Lava stalactites : Figs. 258-260 (|) ; 261, stalagmite (|) ; 262, 

 263, portions showing exterior surface (S) ; 264, 265, sections, 

 showing inside cavities; 266, transverse section (4). E.S.Dana. 



gypsum (CaO.SOs + 2 aq) by combination with the 

 lime, as well as Glauber salt or sodium sulphate 

 (Na20. SO3. 10 aq) by combination with the soda ; 

 and also potassium sulphate (K2O.SO3) by combina- 

 tion with the potash. Glauber salt and gypsum are 

 common about the f umaroles and in the caverns of the 

 crater and lava-streams of Hawaii, and the aluminum 

 salts or alums with some gypsum, at Vesuvius. 



Besides these, numerous chlorides occur in the 

 Vesuvian f umaroles ; e.g., common salt or sodium 

 chloride (NaCl), iron chloride (FeCls), and potassium, 

 ammonium, copper, manganese, and other chlorides. 



Magnetite (re304) and hematite (Fe203) are also 

 f umarole products. At Vesuvius the crystals of these 

 iron oxides are attributed to the reaction of the steam 

 on the iron chloride. Deville and Fouque also report 

 hydrogen and hydrocarbon gas as given out at Torre 

 del Greco in 1861. The hydrocarbon gas could well 

 come from organic materials taken in with the sea 

 water. 



