EOCENE PERIOD. 
[Ch. XXII. 
Eocene deposits originated while the chalk and other secondary 
rocks were rising from the deep and wasting away. 
Earthquakes during the Eocene period. — We have pointed 
out, in a former chapter, our reasons for concluding that the 
Paris basin was a theatre of subterranean convulsions during 
the Eocene period, the older beds of the calcaire grossier 
having been raised and exposed to the action of the waves 
before, or at least during, the deposition of the upper or second 
marine group *. These convulsions were doubtless connected 
with that depression which let in the sea upon the second fresh- 
water formation, and gave rise to the superposition of the 
upper marine beds. We have also demonstrated, in a pre- 
ceding chapter, that some of the earlier volcanic eruptions in 
Auvergne happened before the Eocene species of animals were 
extinct, and we suggested that the great lakes of Central France 
may have been drained by alterations of level which accompa- 
nied the outbreak of those earlier Eocene volcanos of Auvergne. 
We ought not, therefore, to be surprised if we discover proofs 
that the south-east of England participated in the earthquakes 
which seem to have extended at that time over a considerable 
part of the neighbouring continent; and we may refer the 
alternation of marine and fresh-water beds in the Isle of Wisht 
and coast of Hampshire, to changes of level analogous to those 
which gave rise to the intercalation of the upper marine for- 
mation in the Paris basin. 
Why the English Eocene strata rise nearly as high as the 
denuded secondary districts. — Those geologists who have 
hitherto regarded the rise and denudation of the lands in 
the south-east of England as events posterior in date to the 
deposition of the London clay, will object to the foregoing 
reasoning, that not only certain outlying patches of tertiary 
strata, but even the central parts of the London and Hamp- 
shire basins, attain very considerable altitudes above the level 
of the sea. Thus the London clay at Highbeach, in Essex, 
reaches the height of 750 feet, an elevation exceeding that 
* See above, p. 248. 
