68 



That any rock whatever was originally igneous, is a gratuitous as- 

 sumption. Lavas themselves may be, and probably are, in very many 

 cases, Rocks not originally igneous, but Rocks which have been ex^ 

 posed at one time or other to the action of fire. 



Granite is one of the rocks most usually considered as an Agent in 

 Elevation, for what reason I am at a loss to discover. Solid Granite 

 has no inherent principle of motion ; if it move, it can only be by vir- 

 tue of the impulsion it has received from some other body, not in con- 

 sequence of its igneous origin or its want of stratification. The dis- 

 turbances of strata that adjoin granite are not more constant, nor more 

 striking nor more extensive than those of strata far remote from it, as 

 for instance, the limestone shales of Derbyshire or the coal-beds of 

 Liege, Granite veins are too small to raise mountains, and the changes 

 or anomalies that take place at the junction of granite with other 

 rocks, whatever else they may prove, appear to me to have no bear- 

 ing on the question of Elevation. On the other hand, the arguments 

 adduced against the doctrine that Granite while fluid has been forcibly 

 injected from beneath into its present position, are to my mind con- 

 clusive j especially that which is founded on the frequent transition 

 which takes place from Granite to the rocks that adjoin it. We find a 

 continuous series from Granite through Gneiss and Mica slate toClay- 

 slales and the Fossiliferous Slates ; and it is not possible to stop at any 

 point of this progress, and to say in which direction the tendency is 

 strongest. If the gradation were single, the difficulty would be great, 

 but what shall we say to a repetition of such gradations ? In Mr. 

 Weaver's paper on the East of Ireland, two detailed sections are 

 given, in one of which, more than six layers of Granite alternate with 

 as many of Mica slate, and in the other five alternations of the same 

 kind occur, the rocks in each instance forming bands from three to 

 seventy fathoms in thickness. 



The reliance which some authors place on Granite and other un- 

 stratified rocks, as Agents of Elevation, is to me very extraordinary; 

 let one instance suflSce. At Castrogiovanni in Sicily, the Pleiocene 

 Beds attain an altitude of three thousand feet ; hence it has been in- 

 ferred, that since these beds were deposited, there has been formed and 

 introduced into the beds subjacent, a body of Granite, Sienite, Porphyry 

 or other crystalline and unstratified Rocks three thousand feet in thick- 

 ness. This supposition is said to be necessary, but since I do not see 

 the necessity, I will venture another supposition, viz. that Etna has 

 not risen to the height of ten thousand feet without occasioning large 

 cavities in its neighbourhood, some of them submarine ; that Castro- 

 giovanni is situate over one of these ; that the Pleiocene strata have 

 closed the cavity and rendered it water-tight, except on the side of 

 Etna 5 from whose lofty flanks and cloud-capped crater the caverns 

 beneath are regularly supplied by fissures with rain-water and melted 

 snow. Let the author grant me so much, — I ask no more. The 

 hydrostatic paradox has tripped up the hills of the geological one, 

 and I behold my Pleiocene beds mounted at once on a pedestal three 

 thousand feet high, and capable of still further promotion. 



If the explanation here offered meets the case of Castrogiovanni, it 

 will equally account for the height of the tertiary beds in different 



