232 Natural History of Volcanos and Earthquakes. 



thinks himself justified in supposing the caverns beneath the 

 Solfaiara of Puzzuoli to have a subterranean communication 

 with Vesuvius, because whenever the latter is in action, the for- 

 mer is in repose. A slip of paper which Davy threw into the 

 mouth of the Solfatara, during an eruption of Vesuvius, was 

 not rejected, from which he concluded that there must be a de- 

 scending current of air. The subterranean thunder, which is 

 heard at such great distances from beneath Vesuvius, seems to 

 him to indicate the existence of great subterranean caverns, filled 

 with gaseous substances, and that the same caverns which, du- 

 ring the activity of the volcano, continue for a long time to eject 

 enormous quantities of aqueous vapor, must be filled, during its 

 repose, with atmopheric air. In proof of the existence of exten- 

 sive caverns, he mentions those in the limestone of Carniola. 

 Now, as the metals of the earths in the supposed volcanic cav- 

 erns are not only exposed to the action of the air but also to that 

 of aqueous vapor, they will be oxidized at the expense of both, 

 and be converted into lava. He thinks his hypothesis capable of 

 explaining all the phenomena which he observed, 



Davy also touches upon the circumstance, often mentioned by 

 geologists, that almost all great volcanos are situated near the sea.* 

 Supposing their first eruption to have been caused by the action 

 of the sea-water upon the metals of the earths, and the metallic 

 oxides, ejected from the craters in the form of lava, to have left 

 vast caverns, the succeeding eruptions would be effected by the 

 oxidations which would ensue in those caverns. Davy is of 

 opinion that when volcanos lie at a distance from the sea, as 

 those of South America, the water may be furnished from subter- 

 ranean lakes ; for Von Humboldt asserts that some of these vol- 

 canos cast up fish. 



If we wish to ascribe volcanic phenomena to chemical action, 

 says Davy, the oxidation of the metals of the earths and alkalies 



^ That volcanos may act at a great distance from the sea is proved by the Pesckan 

 in the centre o? Asia, which is 260 geographical miles distant from any great sea, 

 and from which streams of lava have issued within the period of om- history. Even 

 the opinion that the vicinity of extensive lakes operates on the volcanos of Central 

 Asia, in the same manner as the ocean, is unfounded. The volcano of Turfan is 

 surrounded by very inconsiderable lakes, and the Lake of Temartu or TssiJmd, 

 which is not twice as large as the Lake of Geneva, lies fully 25 geographical miles 

 from Pesckan. See also Girardin in opposition to Davy's hypothesis in Jameson's 

 Phil. Journ. vol. ix, p. 136. 



