THE "RED-HILLS" OF CANVEY ISLAND. 57
the case of the briquetage found on the Canvey sites, Prof.
John Percival writes:—
"In my opinion the impressions of 'husks' present are
"the impressions of the glumes of wheat. . . . In
"addition, there are impressions of short pieces of straw and
"possibly leaves, doubtless of this cereal. The straw appears
"to have been cut into short lengths before mixing with the
"clay."
If we consider an extreme case, a piece of ware heated so
intensely that all the pores become filled with molten material
(which afterwards solidifies) has an apparent density approaching
2.6, which is roughly the same as the true specific gravity.
The average apparent density of "briquetage" is 1.38,
that of the less crude "domestic" ware 1.60. The porosity,
per cent, of the two types will then be :—
App. Dens. Volume of Pores Volume of Solid
Ware per cent. per cent.
"Briquetage" (b) 1.38 47 53
" Domestic" (c) 1.60 39 61
Molten and
Cooled Clay 2.60 — 100
The results recorded in the Graphs are regarded as affording
an additional reason for considering the "briquetage" and
"domestic" wares as distinct types, and not as accidental
variants produced by an inferior technique.
Consideration of the general' character of the crude red
ware shows that the technique involved in its manufacture is
very similar to that in use at modern brickfields that continue
ancient practice : both yield products manufactured from
"clay" locally dug, largely mixed with combustible matter
and fired in the "open." Similar methods of manufacture
yield similar products, and the hand-made stock brick of today
may be profitably compared with the hand-made pot, manu-
factured on the Red-Hill sites nineteen centuries ago.
The apparent density of the yellow stock brick made at
Buckhurst Hill by Messrs. French, Ltd. is 1.6, a figure that is
identical with that of the "domestic" Red Ware (c).
B