NEOLITHIC SITES IN UPPER VALLEY OF ESSEX CAM. 53
THE VALLEY OF THE ESSEX CAM.
The sites to be described are all situated in the drainage
area of the Cam, and they are, with the single exception of
Coploe Hill, within the County boundary.
The Cam takes its origin in a series of field ditches around
the villages of Elsenham and Henham. Elsenham is situated
on the water parting of the Cam and the Stort. The stream
therefore cuts back into the Chalk escarpment for a distance of
about ten miles before it debouches upon the. flat alluvial valley
north of the Cambridge village of Ickleton. It has therefore
the character of an obsequent stream and there is evidence that
in glacial or pre-glacial times a gorge, now filled with glacial
debris, existed through the Chalk Downs and may have drained
much of the fenland area south into the Thames estuary. (1.)
The head of the highest stream course is situated at a height of
390 ft. O.D. and its level at the county boundary at Ickleton is
approximately 100ft. O.D. The real source is situated at
Newport, about seven miles from this spot, and is at approxi-
mately 200ft. O.D. From the highest point on the stream
course running water only occurs in times of rain, but just south
of the village of Newport permanent springs exist which main-
tain a constant supply of water throughout the year. Above
the 300ft. contour line water occurs in ponds and undrained
hollows. On the east, secondary valleys enter the main valley
at Newport from Debden, and north and south of Audley End
Mansion where the Fulfen and Walden Slades enter the main
stream. On the west, the Cam receives the drainage of the Arkes-
den Valley at Newport, of the Elmdon Valley at Wenden, of a
small valley from Strethall, and of two long valleys at Ickleton.
All these secondary valleys are characterized by the fact that
their drainage originates in field ditches on the clay-capped
hill-tops and their channels are dry during the greater part
of the year. Near their mouths permanent springs are found
at approximately 200ft. O.D.
The general elevation of the escarpment and its subsidiary
ridges is between 300 and 400ft. O.D., but a height of about
490ft. is reached near High Wood on the extreme west of the
area. The slopes are gentle and rounded, decreasing in steep-
ness towards the north. Below the spring heads a narrow