382 M. L. Elie de Beaumount on the Structure and 



of time, as Brydone long ago remarked, the products of the 

 eruptions have accumulated round the foundation of the build- 

 ing only to the insignificant height of two yards. The rent of 

 which I have spoken above, in changing the relative level of the 

 two segments of the Piano del Lag-o, caused at once a change of 

 form more considerable than had resulted from the accumulated 

 products of the eruptions of ages. This change of relative level 

 proves, that Etna does not repose on immoveable foundations, 

 and that the segments into which the meridional rents divide it, 

 are susceptible of a certain change of position. Is the total 

 amount of movement which the segments of Etna have under- 

 gone in consequence of the " etoilemenf which occurred in 

 1832, to be regarded as a sinking or as a *' soulevement''' ? 

 Measures of height would here be of great assistance, if it were 

 possible to give them sufficient precision ; but in their absence, 

 it appears to me that the question may be resolved by a very 

 simple mode of reasoning. The walls of the fractures being se- 

 parated, it is evident that the surface of the mountain has under- 

 gone an increase of size, and that this enlargement necessarily 

 presupposes a tumefaction. The mountain has therefore been 

 ebvated, and to an extent which might easily be calculated if 

 the breadth and length of the fissures were exactly known. 

 This amount of elevation is evidently very small, but still the 

 mere existence of such a change is an important fact. The 

 ejected volcanic matter which accumulates on the central gib- 

 bosity of Etna, increases its height with extreme slowness, since 

 the lower part of the Torre del Filosofo is still visible after a 

 lapse of 2000 years ; and, indeed, extremely precise measure- 

 ments would evidently be necessary, to ascertain if, at the pre- 

 sent day, and tmder our ozvn eyes, eruptions contribute more 

 tha7i " sotdevemens'"'' to increase the size of Etna. 



Part II. — Divisions of the Rocks of Etna into six Forma- 

 tions. — Mineralogists have often complained of the monotony of 

 Etna ; but, in the eyes of a geologist, the mountain presents 

 great variety. Six formations at least can be distinguished, 

 viz. : 



First, The rocks termed Primitive, which do not appear any 

 where at the surface, but whose existence beneath is indicated 



