82 NKWKR PLTOCKN'E PERIOD. [Cli. VII. 



explosions. We may., therefore, suppose this volcanic action 

 to have been as independent of the modern vents of Etna, as 

 that which mve rise to the analogous formations in the Val di 



O O 



Noto. It is quite evident that the lavas of the Cyclopian isles 

 are not the lower extremities of currents which flowed down 

 from the highest crater of Etna, or from the region where 

 lateral eruptions are now frequent, lavas which, after entering 

 the sea. were afterwards upraised into their present position. 

 It is more probable that the basalts of the Bay of Trezza, and 

 those along the southern foot of Etna, at La Motta, Aderno, 

 Patcrno, Licodia, and other places, originated in the same sea 

 in which the eruptions of the Val di Noto took place. 



There are, however, as we have observed., no sections to 

 prove that the central and oldest parts of Etna repose on similar 

 submarine formations. The modern lavas of the volcano arc 

 continually extending their area,, and covering, from time to 

 time, a larger portion of the marine strata ; but we know not 

 where this operation commenced, so that we cannot demonstrate 

 the posteriority of the whole cone to these newer Pliocene 

 strata. 



We might imagine that when the volcanos of the Val di Noto 

 were in activity, and when the eruptions of the Bay of Trezza 

 were taking place, Etna already existed as a volcano, the 

 upper part only of the cone projecting above the level of the 

 waters, as in the case of Stromboli at present. By such an 

 hypothesis, we might refer the origin of the older part of Etna 

 to the same period as that of the sedimentary strata and vol- 

 canic rocks of the Val di Noto. 



But, for our own part, we see no grounds for inclining to 

 such a theory, since we must admit that a sufficient scries of 

 ages has elapsed since the limestone of the Val di Noto was de- 

 posited, to allow the same to be elevated to the height of from 

 two thousand to three thousand feet, in which case there may 

 also have been- sufficient time for the growth of a volcanic pile 

 like Etna, since the newer Pliocene strata now seen at the base 

 of the volcano originated. 



