320 
EOCENE PERIOD. 
[Ch. XXII. 
if it could be assumed that there were ancient causes differing 
from those which are now in operation. But if we substitute 
the phrase, existing causes, we shall find that the argument 
now controverted amounts to little more than this, 4 that in a 
country free from subterranean movements, the action of run- 
ning water is so trifling that it could never hollow out, in any 
lapse of ages, a deep system of valleys, and, therefore, no known 
combination of existing causes could ever have given rise to 
our present valleys ! 1 
The advocates of these doctrines, in their anxiety to point 
out the supposed absurdity of attributing to ordinary causes 
those inequalities of hill and dale, which now diversify the 
earth's surface, have too often kept entirely out of view the 
many recorded examples of elevations and subsidences of land 
during earthquakes, the frequent Assuring of mountains, and 
opening of chasms, the damming up of rivers by landslips, 
the deflection of streams from their original courses, and more 
important, perhaps, than all these, the denuding power of the 
ocean, during the rise of our continents from the deep. Few 
of the ordinary causes of change, whether igneous or aqueous, 
can be observed to act with their full intensity in any one place 
at the same time ; hence it is easy to persuade those who 
have not reflected long and profoundly on the working of 
the numerous igneous and aqueous agents, that they are en- 
tirely inadequate to bring about any important fluctuations in 
the configuration of the earth's surface. 
Recapitulation. — We shall now briefly recapitulate the con- 
clusions to which we have arrived respecting the geology of 
the south-east of England, in reference to the nature and origin 
of the Eocene formations considered in this and the two pre- 
ceding chapters. 
h In the first place, it appears that the tertiary strata rest 
exclusively upon the chalk, and consist, with some trifling ex- 
ceptions, of alternations of clay and sand. 
2. The organic remains agree with those of the Paris basin, 
but the mineral character of the deposit is extremely different, 
