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CHAPTER VI. 
Newer Pliocene formations — Reasons for considering in the first place the more 
modern periods — Geological structure of Sicily — Formations of the Val di Noto 
of newer Pliocene period — Divisible into three groups — Great limestone — 
Schistose and arenaceous limestone — Blue marl with shells — Strata subjacent 
to the above — Volcanic rocks of the Val di Noto — Dikes — Tuffs and Peperinos 
— Volcanic conglomerates — Proofs of long intervals between volcanic eruptions 
— Dip and direction of newer Pliocene strata of Sicily. 
NEWER PLIOCENE FORMATIONS. 
Haying endeavoured, in the last chapter, to explain the prin- 
ciples on which the different tertiary formations may be ar- 
ranged in chronological order, we shall now proceed to consider 
the newest division of formations, or that which we have named 
the newer Pliocene. 
It may appear to some of our readers, that we reverse the 
natural order of historical research by thus describing, in the 
first place, the monuments of a period which immediately pre- 
ceded our own era, and passing afterwards to the events of 
antecedent ages. But, in the present state of our science, this 
retrospective order of inquiry is the only one which can con- 
duct us gradually from the known to the unknown, from the 
simple to the more complex phenomena. We have already 
explained our reasons for beginning this work with an exami- 
nation, in the first two volumes, of the events of the recent 
epoch, from which the greater number of rules of interpretation 
in geology may be derived. The formations of the newer 
Pliocene period will be considered next in order, because these 
have undergone the least degree of alteration, both in position 
and internal structure, subsequently to their origin. They are 
monuments of which the characters are more easily deciphered 
than those belonging to more remote periods, for they have been 
less mutilated by the hand of time. The organic remains, more 
