274 THE ESSEX NATURALIST.
The Westland Green gravel is a well-stratified deposit of
gravel and sand, about 12 feet thick, for the most part without
trace of glacial disturbance. The highest point of the surface
rose (before being removed by the excavation) to three or four
feet above the 350-foot contour. Apart from flint (63 per cent
Tertiary pebbles + 17 per cent weathered flint) the most
conspicuous constituent of the gravel is white vein quartz (10
per cent), which occurs not only in pebbles, but in many larger
boulders up to one foot diameter. There are three or four
per cent of pebbles from the Bunter, which are certainly from the
west, and the remaining six to seven per cent is made up of
sandstones, hard grits, Tertiary conglomerate and Sarsen, fresh
flint nodules and, most important of all, less than one per cent
of volcanic rocks belonging to the group formerly called felsitic,
like those of Wales and the West Midlands.
As the above provisional inference is one of some theoretical
interest, I have placed typical samples of this group of supposed
western rocks in our Museum for comparison when further
evidences become available.
The large gravel workings have partly obscured a hill fort of
Iron Age type which surrounds the same gravel knoll, although
it is not marked on the Ordnance map. At the south-west
corner of the camp the silting of the fosse contained much
Romano-British pottery down to five feet below the present
surface ; there is also much pottery of the same period about
a quarter of a mile south-west of the camp, on ploughland, and
this is certainly a site worth investigation.
I am greatly indebted to Mr. Foster, the owner of the pit,
for giving me every facility to carry on the work here.
I have also found the western type of volcanic rocks at Silver
End, where more work needs to be done. It may be that this
gravel is later, and the western erratics are derivatives, or it
might be an original deposit lowered in level by the inland
extension of the Pliocene Suffolk coast submergence. Moreover,
there is further possible complexity illustrated by the fact that,
at the present day, large continental rivers leave contemporary
deposits through a vertical range of 100 feet, from the river-bed
to the higher flood-level that is attained from time to time.
Pledgdon Sandpit (Various Dates).—This is situated less
than half a mile north-east of Elsenham Cross, and is mainly
interesting as giving an unusual sequence of prehistoric relics,
although there is no evidence of important occupation at any
of the periods represented. The pit is worked in Glacial sand,
which contains many large rolled boulders of the plastic clay of