EVOLUTION OF COASTAL DRAINAGE OF ESSEX. 37
as a whole. The matter of the present brief paper is neither so
extensive in its scope, nor so ambitious in its conclusions, as that
brilliant work of Professor Gregory, but embodies the result of
research recently carried out in Eastern Essex. Another member
of the Essex Field Club, Dr. Wooldridge, has already read
before the Club several papers dealing with his detailed investi-
gations into various aspects of the hydrology and geology of
Essex,3 and the present writer has attempted to add to his work.
It should be stated that free access has been had to Dr.
Wooldridge's work, and the writer would like to express his
thanks for the kindly help and valuable advice received from
him when pursuing this work under his direction.
In the following pages it is proposed to consider the evolution
of the eastern Essex drainage system from the Mid-Pliocene
times to the present day.
There are two principal methods whereby the courses of
early rivers may be reconstructed. One may consider the
evidence afforded by the presence of peneplanes,3 or that
provided by sands or gravels of equal geological age. In many
instances the two methods provide some sort of check. It is
an acknowledged fact that as a river approaches maturity the
transverse profile of its basin becomes comparable to a very
much flattened "V," thus giving rise to an almost level terrain
or peneplane. Furthermore, the periodic floodings that usually
occur along the flood-plain of the river result in the accumulation
of river gravels and sands. By reconstructing the once existing
flattened "V"-shaped basins from the remains of the peneplanes
it is possible to recover the valley-bottom lines, and so outline
the main stream and chief tributaries. The presence of valley
gravels of equal geological age gives additional evidence in
support of the so-formed river plan. It will be obvious that
any negative sea movement obtaining after the formation of the
peneplane will rejuvenate the river and cause the cycle of erosion
to begin again. In this manner the earlier peneplane will be
partially, and possibly entirely, eroded away. Areas of river
gravel belonging to the former stage will be certain to suffer the
same fate unless the main stream radically shifts its position.
Eastern Essex is fortunate in that the main stream has
2 Essex Naturalist. Vol. xxi., etc. Wooldridge, S. W.
3 The term Peneplane has been applied in these pages to the almost level country formed
by the basin of a mature river. See Hobbs, Earth Features and their Meaning, p. 171.