Chemical Theory of Volcanos. 295 



ingredient is rarely altogether absent in any samples which it 

 has fallen to my lot to examine. 



5th Objection. — No nitrogen, according to Boussingault, is 

 evolved from the volcanos under the equator, as would be the 

 case if any process of oxydation were going on in which atmo- 

 spheric air co-operated. 



Ansiver, — The nitrogen remaining after the atmospheric air 

 had been robbed of its oxygen, by the inflammable bodies pre- 

 sent, may reach the air either in a separate condition, or united 

 with hydrogen in the form of ammonia. The former I have 

 generally found to be the case in thermal springs connected 

 with volcanos in an extinct or languid condition — the latter in 

 the craters or fumaroles of those still in a state of greater or 

 less activity. I do not wonder therefore, that Boussingault 

 should have rarely detected nitrogen in the volcanos of the 

 equator,* but I should expect that sal-ammonia may, never- 

 theless, be exhaled from some of them. If this be not the case, 

 it is still possible that the sal-ammoniac sublimed may have 

 been accumulated within some of the vast cavities existing in 

 the interior of the volcano, so that the occasional absence of 

 nitrogen seems less difficult of explanation in accordance with 

 the chemical theory, than the frequent association of it with 

 volcanos is, if we do not have recourse to this hypothesis. 



Gth Objection. — The metals of the earths are not sufficiently 

 ox4dizable to kindle on the access of water, and to produce the 

 intense heat which would be necessary for producing and lique- 

 fying lavas. 



^n5re?er.|r-Silicon, though when pure it is incapable of de- 

 com|X)sing water, and is incombustible in oxygen, yet kindles 

 readily, when united either with a little hydrogen or with alka- 

 line carbonates. Aluminium even by itself burns brilliantly 

 when heated above redness, and dissolves with the evolution of 

 hydrogen in very dilute solutions of potass. 



Calcium and magnesium appear to be still more inflamma- 

 ble, and the bases of the alkalies, present along, and perhaps 

 in combination with them, might, whenever water obtained ac- 



* In two instances it was present. 



