BIRCH GROVES OF EPPING FOREST.
71
under Staples Hill, evidences of a series of springs, thrown out
on both sides of the valley, were observed. The level at which
these springs appear is about, or rather below, the 200 feet
contour and they probably indicate the presence of some per-
meable bed included in the London Clay."1 Quite a number
of springs, marked "rises" on the 6" Ordnance Survey Map,
1921, issue from points at very short distances from either side
of the Epping Road, which runs roughly parallel to, and within a
quarter of a mile from, the watershed between the Lea and the
Roding. The greater number, practically all, of these streams,
follow a south-eastward course and form part of the drainage
system of the latter river. They greatly enhance the picturesque
beauty of the Forest, for several of the more secluded glades, or
"slades," due to their action, afford a delightful variety of
scene that can be enjoyed only by those who wander from the
more frequented routes through the upper woodlands.
The rainfall, in the near neighbourhood of Epping town, based
on an average of thirty-five years, 1876 to 1910, is the highest for
Essex.
"The higher ridges between the Lea and Roding valleys,
south of Harlow, extending" from north-east to south-west for
15 miles, and narrowing from 9 miles in width on the north to a
mere point in the south, includes the highest rainfall of Essex.
The 25" isohyetal surrounds this area running at an elevation
of about 150 feet in the south to something over 250 feet in the
north, while the highest ridge, on which Epping Forest stands,
appears to have a rainfall exceeding 27.5 ins. at elevations about
350 feet."2 The following table shows rainfall for the years
1916-20 at stations on the forest area at different levels, but at
only a few miles distance from each other.
1 Proc. Geol. Assoc, 1910, vol. xxi., pt. 8, p. 452.
2 Whitaker and Thresh, Water Supply of Essex, 1916, p. 41.