548 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 2, 



that its truth adds another argument against their theory of the 



upheaval of volcanic mountains, and supports the opposite view which, 

 in common with Mr. Darwin *, I entertain, that there is " local an- 

 tagonism," rather than coincidence, between direct elevation and 

 volcanic action, — that " dislocations on a large scale are rare in vol- 

 canic districts ; " or, as M. Constant Prevost expresses it, " Les pro- 

 duits volcaniques n'ont que localement, et rarement meme, derange 

 le sol a travers lequel ils se sont fait jourf." 



And on all these grounds it is submitted that the theory of eleva- 

 tion-craters of MM. de Beaumont and Dufrenoy, the Erhehungs- 

 kraters of de Buch, the " bubble-shaped swelling-up of horizontal 

 volcanic strata " of Humboldt, as applied by them to account for the 

 formation of volcanic mountains, is an unnecessary and untenable 

 hj^othesis, which, by introducing vagueness and uncertainty into 

 the views hitherto generally entertained by geologists of the laws 

 of volcanic action, offers a serious impediment to the advance of 

 sound geology. 



For let no one imagine that this question is one of minor im- 

 portance, affecting the theory of volcanos only, and that it may 

 be safely left in abeyance while the other great departments of 

 geology are making safe and certain progress. It is a question 

 that vitally affects the whole theory of geological dynamics. If 

 we are to believe that such stupendous mountain- masses as Etna, 

 Teneriffe, Chimborazo, Elburz, and the other great volcanos of the 

 two hemispheres, were each of them elevated suddenly, and at one 

 stroke (crun seul coup, in the words of Elie de Beaumont when 

 speaking of Etna), by the expansion of a single great bubble of 

 elastic vapour — and that consequently they are even now mere 

 arched crusts covering a vast hoUow void or blister, — of course such 

 a behef must largely influence the views of geologists in regard 

 to the machinery by which the great terrestrial mountain-ranges, 

 other than volcanic, have been elevated, and the time occupied by 

 that process. The notion of the sudden and simultaneous upburst 

 of the great Alpine chains of the old or new worlds from the 

 bottoms of tertiary or secondary oceans to the vast heights which 

 they now obtain, would, in this case, appear quite in the order of 

 Nature, the probability of such extraordinary events being supported 

 by the analogy of volcanic mountains. And it is obvious how the 

 supposition that, beneath these suddenly- elevated tracts, vacuities of 

 corresponding magnitude probably exist, must affect the theory of 

 superficial subsidences. 



On the other hand, if we come, as I beKeve we must, to the con- 

 clusion that volcanic mountains have been slowly built up by the 

 gradual accumulation, layer above layer, of the products of succes- 

 sive intermittent eruptions from the same or contiguous vents, very 

 slightly, if at all, affected by direct upheaval, a strong ground of 

 analogy will be laid for the belief that the elevation of the great 

 non-volcanic mountain-ranges of the globe, and the changes of level 

 of the other rocks which exhibit signs of displacement, have likewise 



* "Volcanic Islands, p. 78. t Mem. Soc. Geol. de France, ii, 



