296 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 20, 



In reply to this, it may be sufficient to remark, that we have no 

 evidence of the existence of such materials in volcanos generally, and 

 that, if the ammonia evolved had been derived from such sources, it 

 ought to he accompanied with bituminous exhalations, with carbu- 

 retted hydrogen, and with other products arising from the distillation 

 of such materials which have never been observed to be present*. 



I will proceed, then, to consider the second hypothesis, that of Pro- 

 fessor Bunsen ; namely, that the lava, in flowing over the herbage 

 existing on the surface of the land which it invaded, had caused the 

 conversion of the nitrogenized matter present in it into ammonia, 

 which, meeting with muriatic acid, a gas constantly present in vol- 

 canos when in a state of activity, was sublimed through the crevices 

 of the lava-current in the form of sal-ammoniac. 



Now, without pausing to consider how far the largeness of the 

 quantity of sal-ammoniac evolved may be consistent with such an 

 hypothesis, I will merely observe that its validity depends altogether 

 upon the question whether the salt is confined to the lava-currents, 

 or has been met with likewise amongst the products derived from 

 the crater itself. 



In my memoir on the eruption of Vesuvius in 1844, published in 

 the • Philosophical Transactions,' I have already stated the latter 

 to be the fact ; but it has since been denied with reference to the 

 volcanos of Iceland by Bunsen, and disputed in the case of Vesu- 

 vius by Scacchi, one of the most distinguished observers of volcanic 

 phenomena at present in Naples. • 



It nevertheless appears at length to be substantiated on good 

 authority, by the recent researches of Palmuri with respect to the 

 products of the eruption or series of eruptions which has been going 

 on for several months past, and which has not yet terminated. 



We are therefore driven to resort to some other solution, which 

 must be independent of the supposed presence of organic matter in 

 any form ; for undoubtedly nothing of the kind can exist within the 

 focus at which the volcanic operations have been for so long a 

 period carried on. 



The hypothesis I myself brought forward some years ago to 

 account for the phenomenon, and which assumed that gaseous hy- 

 drogen, although incapable of combining with nitrogen under ordi- 

 nary pressures, might unite with it under that exercised upon it in 

 the interior of the earth, is not open to the same objections as the 

 two already commented upon ; but it is unlikely, perhaps, to meet 

 with much countenance, until the experiment of bringing the gases 



* Carburetted hydrogen was stated by myself ('Volcanos,' p. 267 ; from per- 

 sonal observations made in 1824, embodied in my memoir on Sicily, published in 

 1 Jameson's Journal ') to be abundant in certain lakes situated near the base of 

 Etna, as well as at Macaluba in the centre of the island. This M. Deville, in his 

 Memoir (' Ann. de Chim.' Jan. 1858, p. 62), has confirmed, stating with great 

 apparent accuracy the proportion which this gas bears to others present. But 

 these latter evidently belong to the class of " Salses," and must be distinguished 

 from true volcanos, in which carburetted hydrogen has, I believe, never yet been 

 detected.— See my Remarks on Macaluba, ' Volcanos,' 2nd edit. p. 539. 



