Volcanos and Earthquakes. 29 



evolved from volcsinosj besides aqueous vapour, we frequently 

 find sulphureted hydrogen gas, as, for example, from those at 

 the equator ; and from others, as Vesuvius^ muriatic acid gas. 

 But the formation of these gases in the interior of volcanos 

 cannot be conceived without the presence of water. 



If the oxidation of the earthy and alkaline metals were to take 

 place at the expense of water, enormous quantities of hydrogen 

 would be necessarily evolved during volcanic eruptions. But 

 this gas seems never to issue from volcanos. According to the 

 observations of Breislak,* Spallanzani,-}* Monticelli and Co- 

 velli, X Hoffmann, § and Poulett Scrope, || flames are never 

 seen to rise from the crater of Vesuvius, Neither did Gay-Lus- 

 sacH during his stay at Naples in 1805, during which he was 

 a frequent witness of explosions, which raised the fluid lava to 

 a height of above 600 feet, ever observe a combustion of hy- 

 drogen gas. Each explosion was accompanied with dense black 

 columns of smoke, which would have inflamed, had they been 

 composed of hydrogen gas, as they were traversed by bright 

 red-hot masses. According to Boussingault, neither hydrogen, 

 muriatic acid gas, nor nitrogen gas, is evolved from the volcanos, 

 under the equator, in the New World.** In opposition to 

 this evidence, we have the assertions of Von Buch. -f-f- 



Davy's hypothesis does not account for the exhalations of 

 carbonic acid gas (Mofettes), which not only succeed every 

 eruption of Vesuvius, but also occur in the vicinity of extinct 

 volcanos and in places affording unquestionable traces of for- 

 mer volcanic action (Auve7-gne, Vivai'ais, Eifel, Laacher See, 

 Bohemia, and so forth,) % % in amazing quantities, and as far as 

 wecan learn from history, with uninterrupted uniformity. These 



* Lelirbuch der Geologie, transl. into German by Strombeck, vol. iii. 

 p. 117. t Voyages dans les Deux Siciles etc. vol. ii. p. 31. 



X Loco cit. p. 191. § A personal communication. 



!l Considerations on Volcanos. London 1825. 



H Loco cit. p. 420. * * Anal, de Cliim. et de Phys. t. Hi. p. 23. 



ft Loco cit. t. ii. p. 14 1. 



tit Monticelli and Covelli, 1. c. p. 191. Biscliof and Noggerath in Schwoig- 

 ger's Journ. v. xliii. p. 28. Bischof in Schweigger-Seidel's Journ. v. xxvi. 

 p. 120. The same in his Vulcanischen ^lineralquellen. Bonn. 1826, p. 251. 

 Von Buch in Poggendoi*ff's Ann. v, icii, p. 418« 



