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 No to. — 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. 
