Orig'm of Mount Etna. 38S 



by fragments of a granitic rock ejected by the mouths of the 

 volcano. 



The Second Formation, indicated on the relief model by the 

 yellow colour, is composed of calcareous and arenaceous rocks, 

 which constitute chiefly the mountains from which Etna is se- 

 parated by the rivers Simeto and Onohola. These calcareous 

 and arenaceous rocks rise at several points in the inclosed space 

 bounded by these rivers, and the volcanic products repose on 

 the edges of their upturned beds. I believe the greater part of 

 these deposits may be referred to the lower chalk. 



The Third Formation, that indicated by a blue tint, is com- 

 posed of basaltic rocks, which constitute the Cyclopean islands, 

 the hill of Molta-di-Catania, and the columnar escarpments of 

 Paterno, Licodia, Aderno, &c. &c. 



The Fourth Formation, coloured green in the model, includes 

 the deposit of rolled pebbles, forming a line of hills at the junc- 

 tion of the plain of Catania and the first acclivities of Etna. 

 The layers of this mass rise towards Etna under an angle of 4° 

 to 5°, and present to it their escarpment. They seem to be re- 

 ferrible to one of the most recent tertiary deposits which sur- 

 round the Val del Bove. 



The Fifth Formation, indicated by the grey colour, compre- 

 hends the ancient lavas of which the escarpments consist. And, 

 finally, 



The Si:vth Formation, represented by the brown and in some 

 points by a red ochre tint, is composed of the modern ejections, 

 whose mass is daily augmenting. 



Of these six formations, the two last only present themselves in 

 the mountain properly so called, and consequently it is their inves- 

 tigation which interests us more directly; but they are, at the same 

 time, those whose component parts it would be most easy to con- 

 found mineralogically. In one, as in the other, the rocks consist of 

 labrador felspar, of augite, and of peridote (olivine), and in the two 

 formations the state of aggregation of these substances differs only 

 by slight shades. But if, instead of considering these rocks mi- 

 neralogically, we regard them in a geological point of view, that 

 19, as to the general disposition of their masses, we perceive, al- 

 most at the first glance, that they form two systems, which are 

 independent the one of the other ; to employ an expression al. 



