Ch. VI.] GEOLOGICAL STRUCTURE OF SICILY. 63 



especially of this era, are most important, not only as being in 

 a more perfect state of preservation, but also as being chiefly 

 referrible to species now living ; so that their habits are known 

 to us by direct comparison, and not merely by inference from 

 analogy,, as in the case of extinct species. 



Geological structure of Sicily. We shall first describe an 

 extensive district in Sicily, where the newer Pliocene strata are 

 largely developed, and where they are raised to considerable 

 heights above the level of the sea. After presenting the reader 

 with a view of these formations, we shall endeavour to explain 

 the manner in which they originated, and speculate on the 

 subterranean changes of which their present position affords 

 evidence. 



The island of Sicily consists partly of primary and secondary 

 rocks, which occupy, perhaps, about two-thirds of its super- 

 ficial area*, and the remaining part is covered by tertiary 

 formations, which are of great extent in the southern and cen- 

 tral parts of the island, while portions are found bordering 

 nearly the whole of the coasts. 



Formations of the Val di Noto.-If we first turn our atten- 

 tion to the Val di Noto, a district which intervenes between 

 Etna and the southern promontory of Sicily, we find a con- 

 siderable tract, containing within it hills which are from one to 

 two thousand feet in height, entirely composed of limestone, 

 marl, sandstone, and associated volcanic rocks, which belong to 

 the newer Pliocene era. The recent shells of the Mediterra- 

 nean abound throughout the sedimentary strata, and there are 

 abundant proofs that the igneous rocks were the produce of 

 successive submarine eruptions, repeated at intervals during 

 the time when the subaqueous formations were in progress. 



These rising grounds of the Val di Noto are separated from 

 the cone of Etna, and the marine strata whereon it rests, by the 

 low level plain of Catania, just elevated above the level of the 

 sea, and watered by the Simeto, The traveller who passes 



* We may shortly expect a full account of the Geology of this island from 

 Professor Hoffmann, who has devoted more than a year to its examination. 



