82 THE ESSEX NATURALIST
taken place at intervals since the Roman occupation, the
old sea walls now within the island being used as trackways,
e.g., Turtle's Wall from the church to Rugwood. (Brown,
1927.)
Until 1922, when the military road was constructed
between Great Wakering and Foulness, the only communi-
cation between the island and the outside world was by boat
or by a track which ran along the inner edge of the Maplin
Sand, a route only usable for four hours on either side of
low water. The five-mile course of this "sea road" is
marked out by hundreds of broom-like plants, hence its name
"Broomway". The name Maplin for the adjacent sands
probably has a derivation connected with the track, for
"mapple" is a broom of twigs.
The remaining islands of Wallasea, Potton and Haven-
gore are similar in character to Foulness. They all lie below
the high water level of spring tides and are protected from
periodic inundation by an enclosing sea wall.
Towards Shoeburyness, the London Clay reappears at the
coast, where it forms a low cliff overlooking the Maplin
Sands. At the Ness itself and for some distance on either
side of it, there is an extensive recent beach deposit of sand
containing the shells of the common cockle, mussel and
periwinkle. It also extends some distance inland, where it
forms Shoebury Common. (Whitaker, 1889.)
COASTAL PROCESSES AND CHANGES
(i) The Coast from Harwich to Clacton
The northern part of the Essex coast is essentially a
coastline of degradation. As we have seen already, this
stretch is characterised by cliffs of variable height largely
formed of London Clay. This formation, when exposed in
a cliff-face, is subject to considerable denudation, largely the
result of attack by sub-aerial weathering forces. In summer,
when the clay dries out, it rapidly loses its cohesive character
and cracks appear in the ground some distance behind the
cliff edge. In winter, water percolating down these fissures,
coupled with a general rise in the water table, causes the
clay to slump like dough under the force of gravity, the water
acting as a lubricant. The slump usually takes place on a