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DOMAIN XII. VOLCANIC. 



NOME II. VESICULAR LAVA. 



This is the most general and undoubted pro- 

 duct of volcanic fires. The vesicles are some- 

 times of an oblong form, but often spherical, 

 especially in those with a base of siderite, which, 

 even in vitrification, does not assume the fibrous 

 form common to other substances. 



Analysis. From the lava which contains leucite, Vau- 



quelin derived silex 53, argil 18, lime 2, oxyd of 



iron 6, potash about 17. The leucite itself con- 



, tained very little iron, but presented the same 



ingredients as the lava, with 20 of potash. 



Vesicular lava is the most common and cha- 

 racteristic production of volcanoes, among which 

 Etna has been chiefly celebrated for more than 

 two thousand years. The torrents of liquid fire, 

 vaguely mentioned through a long series of 

 learned and illiterate ages, consisted of inflamed 

 vesicular lava. Many were the attempts to ex- 

 plore the source of this phenomenon, the sum- 

 Summit of mit of a mountain so interesting to curiosity and 

 even to science. But the best account is that of 

 Spallanzani, at once a natural philosopher and 

 a mineralogist, and who has sprinkled his de- 

 scription with some learned anecdotes of the his- 



