108 
NEWER PLIOCENE PERIOD. 
[Ch. IX. 
into tuffs and peperinos, nor can we imagine that, under 
enormous pressure, they could have become porous, since we 
observe, that the lava which has cooled down under a moderate 
degree of pressure, in the dikes of Etna and Vesuvius, has a 
compact and porpbyritic texture, and is very rarely porous or 
cellular. No signs of volcanic sand, scoriae breccia, or conglo- 
merate are to be looked for, nor any of stratification, for all 
these imply formation in the atmosphere, or by the agency of 
water. The only proofs that we can expect to find of the 
successive origin of different parts of the fused mass, will be 
confined to the occasional passage of veins through portions 
previously consolidated. This consolidation would take place 
with extreme slowness, when nearer the source of volcanic heat 
and under enormous pressure, so that we must anticipate a 
perfectly crystalline and compact texture in all these subter- 
ranean products. 
Now geologists have discovered, as we before stated, great 
abundance of crystalline and unstratified rocks in various parts 
of the globe, and these masses are particularly laid open to our 
view in those mountainous districts where the crust of the earth 
has undergone the greatest derangement. These rocks vary 
considerably in composition, and have received many names, 
such as granite, syenite, porphyry, and others. That they 
must have been formed by igneous fusion, and at many distinct 
eras, is now admitted ; and their highly crystalline texture is 
such as might result from cooling down slowly from an intensely- 
heated state. They answer, therefore, admirably to the condi- 
tions required by the above hypothesis, and we therefore deem 
it probable that similar rocks have originated in the nether 
regions below the island of Sicily, and have attained a thickness 
of from one thousand to three thousand feet, since the newer 
Pliocene strata were deposited. 
It is, moreover, very probable, that these fused masses have 
come into contact with subaqueous deposits far below the sur- 
face, in which case they may, in the course of ages, have greatly 
