234 Natural History of Volcanos and Earthquakes. 
would be necessarily evolved during volcanic eruptions. But this 
gas seems never to issue from voleanos. According to the ob- 
servations of Breislak,* Spallanzani,t Monticelli and Covelli,t 
offmann,$ and Poulett Scrope,|j flames are never seen to rise 
from the crater of Vesuvius. Neither did Gay-Lussac{ during 
his stay at Naples in 1805, during 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.tt 
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 (Auvergne, Vivarais, Eifel, Laacher See, Bohemia, and 
so forth{tt,) in amazing quantities, and as far as we can learn 
from history, with uninterrupted uniformity. ‘These phenomen® 
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 subterranealt 
cavities without their mixing together. Yet, according to Mon- 
ticelli and Covelli,$$ the Mofettes of Vesuvius contain but lite 
atmospheric air, which seems not to intermix with the carbonie 
acid gas until it reaches the surface. I have examined many 
such exhalations of carbonic acid gas, in the vicinity of extinet 
volcanos, (in the neighborhood of the Laacher See and in the 
oy ee 
* Lehrbuch der Geologie, transl. into German by Strombeck, vol. iii, P- ye 
+ Voyages dans les Deux Siciles, ete. vol. ii, p. 31 ¢ Loco cit. p- . : 
yp. 31. 
§ A personal communication. __|} Considerations on Volcanos. London. 
I Loco cit. p. 420. 
** Ann. de Chim. et de Phys. t. lii, p. 23. tt Loco cit. t. ii, p- 141 
tt Monticelli and Covelli, 1. c. p. 191. Bischof and Néggerath in Schweigge | 
Journ. v. xliii, p. 28. Bischof in Schweigger-Seidel’s Journ. v. xxvi, p- aie is 
same in his Vulcanischen Mineralquellen. Bonn. 1826. p. 251. Von 5 2 
Poggendorff’s Ann. vy. xii, p. 418. §§ Loco cit. p. 194. 
