239
FOWLNESS.1
By W. H. DALTON, F.G.S.
[Read at Field Meeting at Southend, July 13th, 1889.]
[After a few preliminary remarks, the Author continued as
follows :—]
I shall leave the archaeology of the island entirely out of con-
sideration, as it has nothing to do with us as a body of naturalists,
however interesting it may be to some of us as antiquarians.
Similarly I shall leave alone the zoology and botany of the island,
having only my crude schoolboy memoranda thereon as data, and
shall confine myself entirely to the geological aspects of the delta of
which Fowlness forms the principal part, being about 7,000 acres in
extent.
As the River Thames proceeds towards the sea, it bears along
with it much sand and clay, the results of its denuding action on the
soft strata across which it flows. The sand, from its greater weight,
is deposited at the mouth of the estuary, where the velocity of the
stream is checked for six hours out of every twelve by the incoming
tide.
Owing partly to the set of the tidal currents, and partly to the
position of the mouth of the Medway on the Kentish shore, most of
the river-borne sand is accumulated on the northern shore of the
estuary, forming the wide, nearly level expanse of the Maplin Sands,
and the many banks which complicate navigation outside the Nore.
Of course all these banks are parts of one great sheet covering the
sea-bed, and the position of such as rise above low-water mark is
liable to be changed by the variable factors of wind, tidal currents,
and the amount of water in these narrow, land-locked seas. A series
of north-west winds, for instance, will raise the sea level on the
Essex coast two feet or more, and this will considerably affect the
scouring power of the currents. The wind, too, may at one time
co-operate with, and at another oppose, the tendency of the tidal
currents, so that a gale may result in the removal of matter which
six hours previously it would have tended to increase. Hence the
necessity, not only for continual revision of the charts of the coast,
but for compulsory pilotage by resident pilots.
But whilst the sandy portion of the silt of the Thames is thus
deposited at the mouth of the estuary, the clayey matter remains
1 "That is 'the promontory of birds or fowls,'" Camden. Officialdom misspells it Foulness.