140 THE ESSEX NATURALIST.
ware or "wasters" are absent. Salt-making by itself, it is
thought, does not explain the vast quantity of burnt earth nor
the shape and nature of the mounds, and further, that very little
evidence exists in favour of Dr. Flinders Petrie's theory that
sea-weed and marine plants were burnt on the sites for recovery
of soda-ash for soap-making; indeed, one of the most active
and experienced of the early investigators, Mr. Francis W. Reader,
reviewing the evidence in a paper read at a meeting of the
Woolwich Antiquarian Society in November, 1910, considered
that the balance of evidence points to the material having been
brought by water and dumped on the sides of the creeks and
estuaries. "Would any people," he asks, "select ground that
"would be covered twice every twenty-four hours with the sea,
"to construct furnaces and carry on an industry in which fire
"played such an important part?" That the tides did wash
the ground on which the Red-hill mounds are situated is shown,
he says, by the occurrence of bands of tidal silt in most of the
mounds that have been excavated.
In arriving at this conclusion the author of the paper appears
to have attached insufficient weight to evidence that points to a
steady subsidence of the land surface of the Essex coast since
the date of the Roman occupation of Britain.- If it be granted
that subsidence of the coast to the extent of many feet has
occurred since Romano-British times, the areas in question could
not have been submerged twice every twenty-four hours, and
one must look elsewhere for an explanation of the so called bands
of "tidal-silt"; indeed, Mr. W. H. Dalton, himself a member
of the Exploration Committee, states that the precise nature of
the intercalated clay has not been demonstrated.3 An alterna-
tive suggestion is here made that some of the thin bands of clay
found at many of the Canvey sites may be clue to rain-wash.
Experiment shows that the subsoil of the Red-hills has differential
filtering properties. Water charged with clay and sand particles
in suspension readily descends through a layer of the loose
cindery soil, through the compacted fine particles of the burnt
clay water percolates so slowly that suspended particles are
2 W. H. Dalton, "Essex Naturalist," Parts III and IV, Vol. xvi, pp. 96-101. Also,
A. G. Fraxcis, Ibid., Vol. xxiii, 1929-32.
3 W. H. Dalton, Appendix to Report of Exploration Committee, p. 19.