21 2 Dr Daubeny on the Dihivial Theory, 



moved from it, and the rending and fracturing of such as were 

 at a still greater distance ? It seems clear, that as the slow con- 

 ducting power of earthy bodies would prevent the more superfi- 

 cial strata from being affected by the heat kept up beneath 

 them, so their bulk and unequal consistence would preserve 

 them from the same degree of displacement which might be oc- 

 casioned by a similar force, applied to a body of less consider- 

 able thickness, and of a more uniformly unyielding texture. 

 Were it not that the shock caused by the extrication of elastic 

 vapours in the interior of the earth is somewhat moderated by 

 the nature of the materials on which it is exerted, the most 

 trifling earthquake, instead of occasioning only a moderate de- 

 gree of devastation, and sparing, in great measure, even the 

 frail works of man, would throw into confusion the very rocks 

 on which the}^ stand, and reduce the whole country into a state 

 jof primitive chaos. 



iiii Owing, however, to the causes assigned, the strata in an up- 

 lifted chain of mountains, though occasionally fractured and 

 displaced, still retain their distinctness, and are often free from 

 any of the effects due to the direct application of heat ; neither 

 ought we to be surprised if, under similar circumstances, the 

 beds of a volcanic mountain, though uplifted in the same man- 

 ner, retain an equal degree of regularity in their arrangement. 

 H^oThere seems, therefore, no absurdity in attempting to apply 

 Von Buch's theory to volcanic rocks, of whatever materials ihey 

 may chance to be constituted. In the more ordinary case, in- 

 deed, where there is an alternation of beds of scoriae and lava, 

 we are at liberty, no doubt, to choose between this and the con- 

 trary hypothesis, according as the circumstances may appear 

 most favourable to one or the other ; but where the volcano in 

 question is composed of a conical mass of trachyte or domite, 

 elevated in the midst of dissimilar rocks, as we observe in the 

 mountains alluded to in Auvergne, the absence of any other 

 plausible theory to account for the phenomena appears te^^leave 

 us no alternative. > . -j ■■ - 



The prejudice entertained against this theory ^in'Eiygla'nd, 

 seems to me to have arisen in part from Humboldt''s well-known 

 comparison of Jorullo to a vast bladder, blown out by elastic 

 vapours, a metaphor borrowed from Ovid, who applied it to the 



