54 
THE ESSEX NATURALIST. 
alluvial plain is formed in the bottom of the valleys, which in¬ 
creases in width until, north of Ickleton, it merges into the 
flat lands of Cambridgeshire. 
The general geological structure may be summarized as 
Boulder Clay above the 300ft. contour line, Chalk on the hill 
slopes, and Alluvium in the valley bottoms below the spring 
heads. The valley bottoms are fringed at intervals by gravel 
terraces of varying width, and exposures of gravel occur here and 
there on the valley slopes where the mid-glacial Gravels outcrop 
between the Chalk and the Boulder Clay. Small exposures of 
gravel and loam also occasionally occur on the tops of the 
ridges. The Chalk slopes are usually covered with a rainwash 
which is often of a clay-like consistency, but in steep places the 
soil may consist almost entirely of finely powdered chalk. 
It seems probable that in Neolithic times the clay hill-tops 
were covered with damp oak-ash woodland (14), the hollows 
in its recesses being occupied by a swamp flora with numerous- 
ponds and small lakes. The Chalk slopes were clad with grass 
or scrub land with a flora corresponding to that of the New¬ 
market and Royston Heaths (14), but it should be noted that 
the sporadic occurrence of typical beech-wood plants, such 
as the White Helleborine (C ephalanthera grandiflora), points 
to a possible northern extension of the primitive beech wood 
of the Chilterns. The valley bottoms were choked with a swamp 
or wet alder wood flora and there are indications that at New¬ 
port, Wenden and Saffron Walden the side valleys below the 
spring heads were occupied by either incipient fens or shallow 
lakes. 
THE REMAINS OF NEOLITHIC MAN IN THE CAM 
VALLEY. 
Neolithic earthworks in the area are restricted to a few 
doubtful examples only. 
In Grimsditch Wood (2), about i| mile N.N.E. of Saffron. 
Walden Church, there is a rampart and ditch with a cigar-shaped 
mound enclosed in the north corner. It is associated with an 
implementiferous area and is possibly a Neolithic camp. 
The lynchetts or cultivation terraces at Ickleton (3) are 
associated with worked flints, which occur on the flats of 
