128 
NEWER PLIOCENE PERIOD. 
[Ch. X. 
scribed. Masses of alternating lava and tuff, the products of 
submarine eruptions, might on their emergence become hills 
and islands; the level intervening plains might afterwards ap- 
pear, covered partly by the ashes drifted and deposited by 
water, and partly by those which would fall after the laying- 
dry of the tract. The last features imparted to the physical 
geography would be derived from such eruptions in the open 
air as those of Monte Nuovo and the minor cones of Ischia. 
No signs of diluvial waves. — Such a conversion of a large 
tract of sea into land might possibly take place while the sur- 
face of the contiguous country underwent but slight modifica- 
tion. No great wave was caused by the permanent rise of the 
coast near Puzzuoli in the year 1538, because the upheaving 
operation appears to have been effected by a long succession of 
minor shocks *. A series of such movements, therefore, might 
produce an island like Ischia without throwing a diluvial rush 
of waters upon low parts of the neighbouring continent. The 
advocates of paroxysmal elevations may, perhaps, contend that 
the rise of Ischia must have been anterior to the birth of all 
the cones of loose scoriae scattered over the Phlesraean Fields, 
for, according to them, the sudden rise of marine strata causes 
inundations which devastate adjoining continents. But the 
absence of any signs of such floods in the volcanic region of 
Campania does not appear to us to warrant the conclusion, 
either that Ischia was raised previously to the production of 
the volcanic cones, or that it may not have been rising during 
the whole period of their formation. 
We learn from the study of the mutations now in progress, 
that one part of the earth's surface may, for an indefinite 
period, be the scene of continued change, while another, in the 
immediate vicinity, remains stationary. We need go no far- 
ther than our own country to illustrate this principle ; for, 
reasoning from what has taken place in the last ten centuries, 
we must anticipate that in the course of the next 4000 or 5000 
years, a long strip of land, skirting the line of our eastern 
* See vol. i. p. 457, first edition ; p. 527, second edition. 
