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 wilh 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. 



HAVING 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 



