234 Natural History of Volcanos and Earthquakes. 



would be necessarily evolved during volcanic eruptions. But this 

 gas seems never to issue from volcanos. According to the ob- 

 servations of Breislak,* Spallanzani,t Monticelh and Covelli,| 

 Hoffmann,*§> and Poulett Scrope,|j flames are never seen to rise 

 from the crater of Vesuvius. Neither did Gay-LussacIT during 

 his stay at Naples in 1805, daring which he was a frequent wit- 

 ness of explosions, which raised the fluid lava to a height of 

 above 600 feet, ever observe a combustion of hydrogen gas. Each 

 explosion was accompanied with dense black columns of smoke, 

 which would have inflamed, had they been composed of hydro- 

 gen gas, as they were traversed by bright red-hot masses. Ac- 

 cording 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.ff 



Davy's hypothesis does not account for the exhalations of car- 

 bonic 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 former volcanic 

 action {AiLvergne, Vivarais, Eifel, Laacher See, Bohemia, and 

 so forth JJ,) in amazing quantities, and as far as we can learn 

 from history, with uninterrupted uniformity. These phenomena 

 must necessarily be closely connected with volcanic action, and 

 cannot pass unnoticed. 



But these disengagements of cabonic acid gas could not take 

 place in the presence of atmospheric air in those vast subterranean 

 cavities without their mixing together. Yet, according to Mon- 

 ticelh and Covelli, <§)*§> the Mofettes of Vesuvius contain but little 

 atmospheric air, which seems not to intermix with the carbonic 

 acid gas until it reaches the surface. I have examined many 

 such exhalations of carbonic acid gas, in the vicinity of extinct 

 volcanos, (in the neighborhood of the Laacher See and in the 



* Lehrbuch der Geologie, transl. into German by Strombeck, vol. iii, p. 117. 



i Voyages dans les Deux Siciles, etc. vol. ii, p. 31. t Loco cit. p. 191. 



§ A personal communication. || Considerations on Volcanos. London. 1825. 



H Loco cit. p. 420. 



** Ann. de Chim. et de Phys. t. Iii, p. 23. ft Loco cit. t. ii, p. 141. 



U Monticelli and Covelli, 1. c. p. 191. Bischof and Noggerath in Schvveigger's 

 Journ. v. xliii, p. 28. Bischof in Schweigger-Seidel's Journ. v. xxvi, p. 129. The 

 same in his Vulcanischen Mineralquellen. Bonn. 1826. p. 251. Von Buch in 

 PoggendorfF's Ann. V. xii, p. 418. §§ Loco cit. p. 194. 



