NOTES ON THE ANCIENT PHYSIOGRAPHY OF SOUTH ESSEX. 195
Maldon, and a belt of comparatively low ground southward and
eastward of those places. He would also be right in supposing that
at Laindon Hill and around Rayleigh there were isolated patches of
high ground, and that there was much low-lying flat ground towards
the margins of the Thames and of the sea. He would note, besides,
the existence of an alluvial flat of considerable size, north of Stifford,
on the borders of the little stream called the Mardyke, and of
another, of much greater breadth, on the banks of the river Crouch,
east of Burnham and Canewdon.
But though, owing to the fact that the various formations of
South Essex are lying nearly flat, the geological map indicates the
general configuration of the present surface of the ground, it will
shortly be seen that it omits much of the utmost importance if we
desire light on the ancient river systems of the district. For that
purpose we must compare the information afforded by the geological
map with that to be obtained from another coloured or shaded so
as to show the present physical geography of South Essex. Such a
map is published with the present paper.
I have already pointed out that the deposits of gravel and loam
which range from Romford to Upminster, and thence by North and
South Ockendon to Stifford, Stanford-le-hope, and Fobbing, belong
to the present Thames Valley system. Between Fobbing and Leigh,
about Pitsea, the Thames in its meanderings has eroded away its
older deposits, and left in their place the more modern alluvium of
Canvey Island and the marshes eastward of it. At Leigh and
Southend, however, beds of gravel and loam, resembling those seen
from Fobbing westward, again appear (as before stated) and range
thence to Canewdon, Burnham, Southminster, and Bradwell. Mr.
Whitaker, in his Memoir on "The Geology of London and Part of
the Thames Valley" (vol. i., p. 476) has expressed an opinion that
these beds were formed on the western flank of the ancient valley of
the Thames when the right, or eastern, bank of that river existed
where now there is open sea. And I think there can be little,
if any, doubt of the correctness of this determination. Thus the
deposits belonging to the Thames Valley system in Essex lie close
to or within a short distance of the Thames from Southend west-
ward, and on the Essex seaboard between Southend and Bradwell.
The maps giving us geological information about Essex are those
of the older Ordnance Survey, and have no contour lines on them ;
while those of the newer Ordnance Survey have contour lines which