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is 500 feet,” and that 44 the flat arch of the Isle of Thanet is 
not wholly owing to the chalk having been thrown into that 
form, as at least 600 feet of other formations have been denuded 
off that tract.” 
The depression during the BracJclesham period was prolonged 
into that of the Barton Beds , which accordingly are found to 
indicate deeper seas. A remarkable change in the fauna almost 
suddenly takes place. We have an influx of mollusca of a com- 
paratively temperate aspect, recalling strongly those of the 
London Clay, and a migration of the more tropical of the 
Bracklesham forms, only 25 per cent, of the less tropical re- 
maining and mingling with the new fauna. This seems to 
point to the mingling of the waters of the North and South 
Seas, and the submergence or destruction of the dividing isth- 
mus, which we know to have been extremely narrow, since 
deposits of the older seas actually overlapped each other in the 
Isle of Wight. The succeeding sands belong to the same period, 
and, as already remarked, do not necessarily indicate change. 
After this the seas were again severed, and remained so until 
recent times, the English Channel, there is reason to believe, 
having been indeed formed during the human period. 
It is interesting to find that Mr. Sorby, now President of the 
Geological Society, inferred on totally independent grounds — the 
study of evidence of wave and ripple action in the marine and 
estuarine beds of the Isle of Wight — that a great river ran from 
the west into the sea, its estuary including part or the whole of 
the present Isle of Wight, and that the breadth of its estuary 
was there 15 or 20 miles. 44 Yet the dimensions of the river 
were such as to keep the water in general more or less fresh, 
and must have been much greater than any now running in 
England.” He was able to trace the approximate size and 
direction of the shoals, and the axis for the rise and fall of the 
tides, the direction of the freshwater currents and prevailing 
winds, at least those which acted with most force upon the sea. 
This confirmation is of value. 
The whole of the vast fluvio-marine or upper Eocene series, 
100 feet more in vertical thickness than the height of St. Paul’s, 
presents us with the section of a great river delta formed in an 
area of depression, similar, perhaps, to that of the Nile or Granges. 
Each successive deposit seems to have been thrown down over a 
more and more circumscribed area, and by a diminishing volume 
of water. The lowest or Headon Beds alone can be traced across to 
the main land ; whilst the highest Hempstead Beds are almost 
confined to a single hill. These enormous accumulations pre- 
sent us with an unbroken series of events in one spot, extending 
from the middle Eocene to the Miocene age in Europe. During 
this lapse of time we see constant changes and modifications taking 
