HOW WERE THE EOCENES OF ENGLAND DEPOSITED? 285 
interpret the changes in character of the deposits and their 
contents. I wish, however, to impress upon my readers that 
while the foregoing section of the subject is well ascertained 
fact, a portion of the remainder is, for the present, to be con- 
sidered as mere theory and individual opinion. It has not pre- 
viously been laid before men of science, and therefore, although 
it seems to me perfectly consistent, objections may be urged 
against my conclusions. 
We learn from M. Hebert’s writings that the whole group of 
Eocenes in France and Belgium, below the Thanet Sands, and 
of which we have do record in England, were deposited in an 
area alternately sea and dry land, and subject to much oscilla- 
tion. In the intervals between these recurring changes of level, 
deposits were formed, but each change denuded them, so that 
only mere fragments of the original beds now remain. The de- 
posits were formed by a gulf opening into the North Sea which 
itself communicated with the ocean between the Shetland Isles 
and Norway. This sea may have penetrated over portions of 
England and left deposits upon the much eroded Chalk, which 
denudation subsequently carried away. However this may be, 
there can be no doubt whatever that the Thanet Sands were 
littoral deposits of the same sea, and mark a period of depres- 
sion in the London Basin. 
I shall have to speak of the deposits of a Northern and 
Southern Sea. For the present it will suffice merely to suppose 
that the English and St. Greorge’s Channels were dry land in 
these remote times, and to distinguish the seas on each side of 
the barrier respectively as Northern and Southern. Overlying, 
and perhaps partly contemporaneous with, the shallow sea de- 
posits of the Thanet Sand are the English mottled clays belong- 
ing to the Woolwich and Reading Series . In the direction in 
which they are deposited and thin out, we have the first evi- 
dence of the presence of a mighty river flowing from west to 
east and scouring and draining a granitic country. In the es- 
tuarine beds and the lignites around London, we can trace its 
delta and embouchure, whilst the marine sands to the east were 
thrown down by the Northern sea into whichit poured. Through- 
out the whole Eocene time we shall trace the presence of this 
great river, which receded and advanced and changed the direc- 
tion of its outfall in obedience to the continued oscillations 
which this part of its course experienced. 
The next movement, at the close of the Woolwich and 
Reading series, was probably one of slight upheaval, during which 
the south-east of England became land. Depression followed, 
and the Northern Sea gradually reoccupied the tract. The shingle 
and sand banks of the Oldhaven beds mark this change, 
and are the result of the littoral conditions which prevailed 
