80 Notice of Active and Extinct Volcanos. 



its origin is probably from limestone strata, to which the heat 

 gradually penetrates. 



Nitrogen gas is said to have been detected at Vesuvius, 

 and in some other volcanos ; the existence of ammoniacal 

 salts implies that of nitrogen, which may arise from the de- 

 composition of atmospherical air, by combustibles and me- 

 tals, even at a considerable distance from the fire. 



It is proved then, that the gases known to be given out by 

 volcanos, are " muriatic acid, sulphurous acid, sulphuretted 

 hydrogen, carbonic acid, and nitrogen," with an enormous 

 quantity of aqueous vapor, whose condensation produces 

 torrents of rain. We can scarcely doubt, that ammonia and 

 hydrogen must also be present, although pure hydrogen has 

 not been detected. It would of course unite with sulphur, 

 if raised with its hot vapor ; atmospherical air, or decompo- 

 sed water, would produce sulphurous acid, and these two ga- 

 ses producing mutual decomposition, we should observe only 

 that one which was in excess. 



Muriatic acid impairs the inflammability of hydrogen, and 

 might thus prevent its burning. 



The muriatic acid is probably derived from muriate of 

 soda, ignited with hot silex and alumine, and mixed with 

 steam, in which case its alkali would unite with the earths, 

 and its acid would be exhaled. 



Professor Daubeny founds his explanation of the causes of 

 volcanos, upon the very interesting discovery of Sir Hum- 

 phrey Davy, " that the solid constituents of our globe all con- 

 tain some inflammable principle, and owe their present con- 

 dition to the union of this principle with oxygen," and he 

 thinks it by no means improbable, " that at a certain depth, 

 beneath the surface, at which atmospheric air is either wholly 

 or partially excluded, those substances may still exist in their 

 pure unoxidized state." 



As they do not exist, and cannot, at the surface of the 

 ground, we cannot expect any analogous phenomena to hap- 

 pen under our observation, and we are, therefore, at liberty to 

 reason strictly with reference to the known action of the sub- 

 stances in question. 



Water having access to them, would be decomposed, great 

 heat would be generated, sufficient to melt the rocks and the 

 stony matter, formed by the oxidizement of the metalloids, 

 immense quantities of gas and of steam would be evolved, 

 and all the mechanical effects so familiar in volcanic erup- 

 tions and earthquakes, would occur. 



