fJ14 Dr Daubeny 07i the Diluvial Theory, 



follow that the only case, which affords us an opportunity of 

 putting our theory to the test, completely confirms it» the first 

 volcanic operations in this place appearing to have caused an 

 upheaving of the rocks within a given area. 



I am, however, as I stated in my work on volcanos, more 

 disposed to reason from the Puy de Dome to Jorullo, than to 

 follow, as most others appear to have done, the opposite line of 

 argument ; granting, with Mr Scrope and Mr Lyell, that the 

 facts which Humboldt has brought forward with respect to this 

 mountain would be insufficient to establish the fact of its having 

 been heaved up, if such a phenomenon be considered as entire- 

 ly without precedent, but contending that, the occurrence of 

 other events of the kind once admitted, there is no longer suf- 

 ficient reason for disputing his conclusions in this particular 

 case. 



Leaving, therefore, the question as to Jorullo to be deter- 

 mined by the opinion we may form with respect to the origin 

 of volcanic mountains in general, I think it may be fairly urged, 

 without any risk of going beyond what our premises warrant, 

 that the doctrine in question, even should it not have been con- 

 firmed by experience, is not contradictory to it ; in which case, 

 if it explains the phenomena exhibited by the cones of trachyte 

 alluded to, we are surely at liberty to adopt it, notwithstanding 

 the absence of any analogous phenomena observed at present, just 

 as the occurrence of huge blocks of granite on the summits of the 

 Jura, and in other situations to which they could not have been 

 brought by rivers, justifies us in supposing an aqueous inunda- 

 tion to have taken place of an extent which we have no expe- 

 rience of in modern times. 



Mr Lyell has, indeed, himself allowed, " that if a single cone 

 could be discovered, composed entirely of marine or lacustrine 

 strata, without a fragment of any igneous rock intermixed, and 

 in the centre a great cavity encircled by a precipitous escarpe- 

 ment, he should be compelled to concede that the cone and cra- 

 ter-like configuration, whatever be its mode of formation, may 

 sometimes have no reference whatever to ordinary volcanic ope- 

 rations." 



Now, to expect the entire absence of igneous products from 

 mountains so constituted seems somewhat unreasonable, for 



