THE ESSEX NATURALIST. 
no 
J - 
It has been estimated that London Clay forms four-fifths 
of the whole surface of Epping Forest, the remaining fifth 
consisting of patches of sand and gravel that cap the clay. 
Within the limits of the plateau the ratio between similar surface 
layers is as 3 : 2. 
Sand and gravel surfaces throughout the Forest are remark¬ 
ably well indicated by the presence of birch grove, birch oak- 
wood, and of small colonies of this tree. These very distinctive 
features did not exist 50 years ago. 
On entering the Forest from Loughton, by way of Earl’s 
Path, a few birches stand as sentinels around the gravel pit, 
now a pond. Beyond this point they increase rapidly in number 
on both sides of the road, but more especially on the western 
side ; they disappear again by the time the Epping road is 
reached. The appearance and disappearance coincide with a 
patch of gravel overlying .the London Clay. This gravel occurs 
just above the 200 feet contour line. It has been described by 
*our Secretary’ as forming part of a high level terrace of the 
Roding. 
The birch grove around the church at High Beach is upon 
pebble gravel (362 feet) that has been broken up by the com¬ 
paratively recent digging of numerous small, shallow, now 
overgrown pits, while the attractive belt of birch that sweeps 
round the church and reservoir on the western side, at a slightly 
lower level, is for the most part on Bagshot beds. Important 
birch groves occur around the Wake Arms and in close proxi¬ 
mity to it, notably one at Jack’s Hill. Here again are numerous 
overgrown gravel pits with a depth of 3 to 4 feet. The honey¬ 
combed nature of this pit area arises from the fact that the 
gravel is deposited in pockets. During a visit to this locality 
in October last, I was able to observe a small excavation that 
was being made by workmen on the side of the Epping road. 
Measurements made at the time gave the following results :— 
Surface soil g" f gravel 30", and a depth of clay removed 4". 
Birch groves occur also at Genesis Slade, Epping Thicks, 
Oak Hill, Piercing Hill, Sand Pit Plain, and on the western 
side of Loughton Camp. These are not confined to the Pebble 
Gravel, but the soil is at least sandy. 
The gravels at Jack’s Hill and its vicinity have a wide 
3 Thompson, Percy G., “ On the Occurrence of Rhaxella Chert in Epping Forest Gravels." 
Essex Naturalist, 1913, pt. x.-xii., vol. xvii. p. 256. 
