248
THE ESSEX NATURALIST.
and there can be no doubt that the actual coastline lay north of
the escarpment crest.
In 1921 Mr. C. J. Gilbert discovered an outlier of typical
Lenham Beds at Littleheath on the Chiltern Hills. The dis-
position and lithology of the beds here are strictly comparable
with those of the Surrey Lenham Beds and no doubt can be
entertained as to the correctness of the correlation. It has
been shewn elsewhere2 that the Littleheath outlier is only one
of a series of such masses occurring on the Chiltern Hills, and
throughout this terrane the relations of the beds closely imitate
those in evidence upon the North Downs. A similar wave-cut
platform is found, inclined towards the centre of the Basin,
and the position of the coastline can be fixed approximately,
lying for the most part south of the escarpment crest, but close
to it.
From the facts outlined above, an important conclusion
may be drawn, viz., that the Lenham sea was a gulf or channel
essentially co-extensive with the London Basin as defined
by the present bounding Chalk-escarpments. Eastwards it
opened into the ancestor of the North Sea (which had come
into being in Miocene times), but as to its westward connections,
if any, we have no positive information as yet.
The elevated situation in which the Lenham Beds are now
found points to a marked subsequent uplift, but the low grad-
ients at which they are disposed on the flanks of the Basin
show that this uplift was of a broad and gentle character, un-
accompanied by any marked deepening of the London syncline,
or uplift of the complementary Wealden arch.3
2. The Pebble Gravel.
The occurrence of Lenham Beds on both flanks of the
London Basin, at elevations which, in the south, range down to
400 ft., renders it probable that beds of the same age cap some
of the higher hills of the central Eocene tract. If we project
the sub-Diestian surface northwards from Kent into Essex,
maintaining the gradient shewn in the former county, it would
pass well below the summits of the Essex hills. This is obviously
2 S. W. Wooldridge, Rep. Brit. Assoc. (1926), p. 353.
3 The writer hopes to publish shortly a fuller account of the relations of the Lenham Beds
in the London Basin. The above is a summary only.