70 
OLDEK PLIOCENE. 
thickness of shallow water Newer Tertiary beds. The axis of 
the Weald, including the Downs near Lenham, has been corre¬ 
spondingly elevated. Suffolk was little affected, and the deposits 
were tlierefore, in that district, thin and largely of organic origin. 
Were we to assume that the present positions of the Pliocene 
deposits of the north-west of Europe represent the relative depths 
at which the beds were originally laid down, a curious difficulty 
would present itself in any attempt to compare the Pliocene and 
recent sea-bottoms. Any deep depressions in the seas around 
England are now filled with cold water and contain an Arctic 
fauna. In similar depths during the Pliocene period one would 
expect to find a similar fauna, unless there existed, as in the 
Mediterranean, a barrier to cut off the Polar currents, or unless 
there was at that time no cold area at the Pole. Neither of these 
explanations seems allowable. 
A few years since the Coralline Crag was generally considered 
to be our only representative of the Older Pliocene period, and as 
it did not rise much above the sea-level, it was often assumed that 
great part of the rest of England was dry land. Now we know 
that Pliocene beds cap the highest parts of the North Downs, and 
indicate a subsidence sufiicient to submerge the whole of the east 
and south of England, except a few hills. We find that, instead 
of the Older Pliocene period being one of elevation, there must 
have been widespread submergence, though the indications of 
irregular movement prevent us feeling confident, in the absence of 
fossiliferous deposits, as to the extent of the submerged area. 
Among the hard rocks of Cornwall denudation does not appear 
much to have changed the general configuration of the country 
since the Older Pliocene period. Moreover the Pliocene deposits 
in that district were probably never continuous or thick, but 
merely formed patches in sheltered places and around the shores, 
the rest of the sea-bottom being rocky. In the south-east and 
east of England, however, the case was different, for the rocks of 
that region are soft and much more easily denuded. The position 
of the Lenham beds, at the very edge of an escarpment, over 600 
feet above the sea, indicates that the great valleys of the Thames 
and Weald have to a large extent been excavated since Pliocene 
times. 
