FAUNA OF THE TERTIARY. 
91 
The blue clay underneath the gravel con-^ 
tains many shells, telling of the ocean which 
once rolled where now the tide of human 
life continually flows. It occupies an ex¬ 
tensive area in Middlesex, and in Hamp¬ 
shire, and affords evidences in several places 
I of the islands and shores of that ancient sea 
in the depths of which it was tranquilly 
deposited. 
Fragments of wood, water-worn and 
pierced by the worm, are sometimes dis¬ 
covered in the district, and the resinous 
products of the fir forests of a former age, 
have also been found in considerable quan¬ 
tities. 
In Sheppey, at the mouth of the river 
Thames, the clay is abundantly fossiliferous, 
yielding the remains of numerous fruits 
and flowers. These bear much resemblance 
to the productions of the tropics, but are 
not absolutely identified with any species in 
actual present existence. 
The first tertiary land concerning which 
we have distinct knowledge, was richly 
-cothed by a vegetation, a good deal of 
'w ose general character is recognised by 
