340 
THE WEALDEN 
could form a delta of such extent as the Wealden, 
it must have required the drainage of a vast con- 
tinent to supply.* An interesting question here 
arises ; what was the nature of the rocks that 
formed the boundaries of this ancient river, lake, 
or estuary ? It would seem most probable, that 
these were composed, in part at least, of the oolite, 
lias, and other secondary strata, and which were 
worn down into the sands and clays of the Wealden : 
but, if this were the case, we should expect to find 
in the conglomerate of Tilgate Forest some traces 
of the peculiar fossils of those formations, and some 
of the harder portions of the rocks in the state of 
pebbles ; whereas, these strata contain rolled masses, 
and gravel, of quartz, jasper, and flinty slate, which 
must have resulted from the disintegration of pri- 
mary, rather than of secondary formations : it 
seems, therefore, most probable, that the Wealden 
is made up of the debris of rocks of various ages.! 
The proofs of the Wealden having been the delta 
of some ancient river, are so fully stated in the pre- 
ceding chapter, that it is unnecessary to dwell upon 
the subject. Of its original extent, our conjectures 
must necessarily be extremely vague : Dr. Fitton 
has, however, ingeniously instituted a comparison 
* Had the fossil vegetables of the Wealden been identical with those 
of the Isle of Portland, it might have been supposed that the latter 
was dry land at the Igiianodon period : but although the vegetable 
remains in both deposits indicate the floras of tropical climates, they 
are totally distinct from each other, and belong to different species and 
genera. 
t Dr. Fitton has a fragment of an ammonite in limestone, from the 
Wealden of the Isle of Wight: oyster shells occur in some of the 
Purlieck strata. 
