071(1 on the Origin qfthe Valleys of Auvergne. 9.V6 



analogous case of the mountain Methone in Argolis, which tra- 

 .ilition; represented as having been heaved up in that manner, 

 no I do not, however, imagine that, by the metaphor in question, 

 anything more was meajit to be conveyed than that the mate- 

 rials of which the mountains consisted had been heaved up 

 whilst in a pasty condition, by elastic vapours, generated during 

 the action of the volcano ; or that any comparison was intended 

 between the relative thickness of the external crust of the cone 

 to a supposed internal cavity, and that of the membrane. of the 

 bladder to the air which distended it. orit ni fc"t«o<j[cv 



^^.')(,The very supposition of one regular vault existing within the 

 mountain is neither a necessary nor even a probable one ; for it 

 is more conceivable that the cavity occupied by the vapours 

 which heaved up these masses of rock should have been subse- 

 quently filled, either wholly or in part, by ejections of lava : 

 but this need not alter our view of the manner in which the 

 mountain aeqviired its conical form, or dispose us to reject an 

 hypothesis, which furnishes us at least with the only plausible 

 explanation that has yet been offered of the circumstances of 

 the case. lo vas 



The objection urged against this tlieory, which is built upon 

 our want of experience of any such event as the elevation of a 

 cone in the manner supposed, loses much of its force when we 

 reflect, how few instances are recorded of new hills having been 

 produced by volcanic agency within the memory of man ; and 

 how totally without examples we are of trachytic cones (to 

 which the theory in question best applies), formed within this 

 comparatively small fraction of the history of the globe. All 

 the active volcanos, indeed, described by scientific travellers, 

 except Jorullo, are known to have begun their eruptions before 

 the existence of authentic records ; for we cannot regard Vesu- 

 vius and the other ignigenous mountains in the neighbourhood 

 of Naples, in any other light than as different vents of one great 

 volcano, or doubt that a similar connexion must exist in other 

 localities between the several craters of the same district. 



Now, if we are willing to adopt the conclusions of the most 

 distinguished naturalist who has hitherto studied the phenome- 

 na of Jorullo, conclusions, I may add, which remain unques- 

 tioned by any traveller who has since visited tlie spot, it will 



