242
FOWLNESS.
most part level, there are, in a few places, depressions, marking
the position of "fleets"; that is, large ponds or creeks in the original
saltings, which have either been kept clear by currents, or have
received no silt since their formation.
The line of old wall mentioned above may be traced north from
the Brick-kilns to the Crouch, whilst in the opposite direction it
may be followed along the road past the School and Church on to
the Lodge Farm, and round through Court's End to the Crouch again.
Between the School and the Church, on the south side of this
line, is a barren, waste piece of ground, about 18 inches below the
level of the adjoining fields, and from this rise, here and there,
grassy mounds. We have only to imagine this waste to be per-
manently instead of intermittently wet, and the scene will be an
exact counterpart of the still unenclosed saltings. Several similar
cases occur in other parts of the island. In such low-lying spots,
where the soil is but a few inches thick, the only vegetation is that
of salt-loving plants.
With such a subsoil, there are, of course, no springs in the island,
but artesian wells are sunk at fourteen of the farms, and the water
rises to the surface. The depth of these wells averages about
420 feet, and the greater part of this is through stiff London Clay,
with 50 or 60 feet of sand and shingle on the top of the clay. Both
sand and shingle being full of salt water, exterior lining pipes are
first driven into the solid clay, and the bore-hole below these is
lined with pipes of smaller diameter. Besides the Septarian nodules
which are met with at intervals in the London Clay, the bottom bed
is often a tough calcareous grit. Some of the wells, however, do
not penetrate to this horizon, but find a scanty supply in some of
the subordinate beds of sand which occur in the lower part of the
London Clay.
The water, as obtained from the above-mentioned wells, is, like all
water from the London Clay, impregnated to a certain extent with
salts of iron, lime, and magnesia in sufficient quantity to render it
unpalatable to those accustomed to drink soft water. It is, however,
better adapted than soft water to all brewing purposes, whether of
malt-liquor, tea, or other beverages.
The depth at which the water-bearing beds under the London
Clay occur varies from point to point with the undulations of the
strata, which appear to constitute a true plane over no extensive area.