XIV.
a channel at the back, receiving the brooklets of
Langenhoe and Peldon, but probably eroded in the
first instance by the Colne, before that river ent
through the eastward extension of the ridge to St.
Osyth Beacon Hill. At that time the saltings and
fresh marshes of Geeton, Fingringhoe, and Langenhoe
probably formed, in time of flood, an extensive lake,
whilst the marshes between West Mersea and Tolles-
bury constituted a still larger sheet of water. The
mud resulting from the waste of the clay cliffs of
Walton, Frinton, and Clacton filled the bay of what
is now the mouth of the Colne, and then passed south-
ward across the estuary of the joint rivers to line the
shore, down to the Thames, with a broad belt of
treacherous ooze, well nigh impassable.
On the inland borders of the saltings behind Mersea,
and westward to Tollesbury Marsh, occur numerous
mounds and levelled patches of burnt earth. They
lie, as a rule, just above the average high-water mark,
or its level, where the saltings have been inclosed, as,
after conversion into marshes, the saltings always
shrink, chiefly from loss of water, to much below their
original level. Many thousands of acres of saltings
along the coasts of Essex are only occasionally covered
by exceptionally high tides, but they are wetted to
varying heights, according to the state of the tides,
every twelve hours. The water readily penetrates,
for the saltings are intersected in every direction by
creeks or cracks, which serve as conduits to admit the
water in flood, and drain it away during ebb.
The mounds consist of a reddish, porous earth, like
disintegrated brick, mixed, in some places freely, with
broken pottery of the rudest type, wood charcoal, or
cinders, and clinkers.
The mounds exist only in the peculiar position
described. Not one is more than five feet above high-
water mark, or reaches to low-water mark. They all
seem singularly uniform in character and composition.
The majority are from two to four-and-a-half-feet in
depth, and have the same appearance at the surface
as when worked down to the base, with the exception,
of course, of the differences made upon the surface by
vegetation, and, in many cases, by centuries of
cultivation. They have not been examined sufficiently
to tell their full number and extent; but the largest
seems to be about thirty acres in area. The majority are
smaller, but still nearly all are of considerable size,
ranging from half-an-acre to five acres or more. The
small ones are generally those most accessible for re-
moval ; and as the neighbouring fields of stiff clay are
improved by the admixture of porous material from
the mounds, they have been dug away for this pur-
pose to a large extent. Even the largest consists
almost entirely of red burnt clay, and contains an