VII.
An analysis of some of the phosphate nodules found
at Beaumont, about seven miles inland, was made by
Mr. R. Phillips, in 1846, and gave the following result :*
Phosphate of lime, with a little oxide of iron.. 56.00
Carbonate of lime .......................... 18.08
Silica........................................ 7.88
Alumina.................................... 6.00
Oxide of Iron................................ 5.38
Carbonaceous matter ........................ 0.44
Moisture.................................... 4.0
Loss....................................... 2.22
100.00
Glacial Drift.— There is little at present known of
interest in the Glacial Drift of this district, which
consists of gravel and sand, with intercalated and
. overlying loamy beds. The latter may represent the
chalky Boulder Clay, under which the gravels pass
to the north and west of Colchester.
Some of the isolated patches of gravel near the
coast may have been re-arranged, if not formed for
the first time, in the earlier part of the long period
that has elapsed since the recession northward of the
arctic conditions of the Glacial Period, but in the
absence of any evidence of postglacial deposition or
disturbance, such gravels must be placed provisionally
with those known to be of an age anterior to the
Boulder Clay.
Post Glacial Beds.—The Boulder Clay throughout
South Britain is of marine origin, having been de-
posited either in open shallow sea, or formed by the
abrasion of coasts by the ice-foot which under Arctic
conditions forms so powerful an engine of destruction.
The gradual amelioration of the climate, doubtless,
progressed from the South, so that whilst the Frost
King still held sway in North Britain, East Anglia,
rising slowly from the sea, began to be carved once
more into hill and valley by streams and rivers. The
earliest deposits formed by these agencies, and left for
our investigation, indicate some differences of geo-
graphical conditions from those now obtaining, and
their contained fossils point to a warmer climate than
the present. Those of the Marks Tey brickyards and of
the Stour Valley, between Manningtree and Harwich,
are somewhat beyond our present district, but may
be mentioned as representing slightly different condi-
tions from those under which were deposited the Post-
Glacial Beds of Clacton-on-Sea.
At the pier, and westward as far as the first Mar-
tello Tower (No. 6) the cliff consists of London Clay
for about half its height, capped with gravel. About
midway in this gravel bed will be seen a line of grass
along a scarcely perceptible ledge. This denotes a
* Lond. Geol. Journ., 1846, p. 17.