88 THE ESSEX NATURALIST
of it as the result of the sea having burst over the present
artificial banks in recent times. (Woodward, 1903.) Steers,
on the other hand, was more conservative and had no
explanation to offer regarding its origin. He states that
there "has been no detailed mapping of the shingle and
dunes (?) and consequently there can be but little reliance
on the trend and nature of the old shingle ridges to help in
studying the evolution of the coast." (Steers, 1946.)
From a cursory study of the map (Fig 2) it might seem
that the ridge represents a former offshore bar which has
migrated landwards under wave attack. When the shoreline
coincided with the present limit of the London Clay outcrop
and formed an open bay between Burnham and Bradwell,
the growth of a submarine sand and shingle bar some distance
offshore may be postulated. Wave action would gradually
raise the bar above sea level and drive it onshore, where it
would form a partial bay bar enclosing a lagoon between it
and the initial shoreline. The lagoon would gradually be
infilled to form the present Dengie, Southminster and Burn-
ham Marshes. The new shoreline would then lie along the
shingle and sand ridge. Further deposition would take place
seaward of the ridge to form a mud flat similar to the Ray
Sand at the present time. After reclamation this would
become the upper marsh between the ridge and the present
sea wall.
All this is hypothetical and there are many objections to
such a theory of origin. It would necessitate waves from
the east-south-east to drive the bar onshore, and this is not
the direction of maximum fetch for this part of the Thames
Estuary. The main movements within the estuary are the
result of tidal stream forces which carry material in the
direction of the flood and ebb tides, i.e., south-west and
north-east. The alignment of Foulness Sand adjacent to the
coast and Barrow and Long Sand in the outer estuary is
in accordance with this movement.
A more reasonable explanation is to regard the feature as
a marsh bar. This is a form produced by marine erosion
of the seaward edge of a marsh on a relatively unexposed
coast. The action of waves is to separate out coarser
materials like sand and shingle present in the mud and silt.
These are then cast up on to the remaining part of the marsh