24 THE ESSEX NATURALIST
the other running towards the southern stream. Between
these ridges is a depression, free from sand but for two small
knolls.
Fig. 2. M.S. sections at 100 yard intervals projected to show trend of
slopes.
The particular configuration of the land, together with the
two contrasting soil types, gives rise to three main habitats.
Firstly, there are the sandy areas which are dry because of
their altitude and the tendency for a sandy soil to drain freely ;
secondly, there are the higher clay soils, fringing the sand,
these also being dry, but not so dry as the sandy areas ; thirdly,
there are the much wetter clay soils of the valleys.
The way in which these three habitat conditions have in-
fluenced the vegetation, is brought out by the distribution
maps, Figs. 4 and 5. Fig. 4 shows the distribution of the
dominant trees, the Oak (Quercus robur and Q. petraea and