260 RHAXELLA-CHERT IN EPPING FOREST GRAVELS.
much too slight to permit of the transport of large pebbles by
fluviatile action alone ; and I am strongly averse to postulating
differential earth movements of comparatively late date in order
to give a greater declivity. This old gravel is certainly water-
laid, and seems to be a Valley Gravel laid down by an ancient
river following approximately the same course as the modern
river Roding ; it is nevertheless not a post-glacial deposit, but
interglacial, and earlier than the Boulder Clay ; and so may
rightly be classed as a "Glacial Gravel."
On the evidence, we may reasonably conclude that this old
river-gravel is largely made up of materials re-sorted from an
earlier Glacial-gravel. The so-called Glacial Period is known to
have been an immensely long epoch, or, rather, a series of epochs,
broken by several mild interglacial periods, themselves of very
long duration.1 During one of the earlier interglacial periods,
and before the advent of the glacier-borne Chalky Boulder Clay,
the older Roding gravels were laid down from materials brought
by ice-action from distant sources lying to the north-west
into the catchment area of the river.
At the time the Roding was laying down its higher ten-aces,
its lower course would appear to have been quite different
from what it now is. It then probably flowed in a south-
westerly direction between Loughton and Buckhurst Hill
and to the north of the latter place,2 thence taking its course
across Fairmead and Chingford Plains to ultimately join with the
Lea, which, like itself, is older than the Chalky Boulder Clay.
The small isolated gravel-patches at Strawberry Hill and Earls
Path (at 244 feet above O.D.), at Hill Wood (at 267 feet above
O.D.), at Warren Hill, Loughton (at just over 200 feet above
O.D.), by Queen Elizabeth's Lodge (at 189 feet above O.D.),
at Cuckoo Pits (at something under 200 feet above O.D.), at
Bury Farm, Sewardstone (at just over 200 feet above O.D.),
at Yardley Hill (at 218 feet above O.D.), and at Friday Hill,
Chingford (at 190 feet above O.D.), are, if my view is correct,
the still remaining evidences of the Roding's earlier course.3
In conclusion, I have to express my indebtedness to Mr.
E. T. Newton, F.R.S., for very kindly confirming my provisional
identifications of the fossil casts in the Rhaxella-chert.
1 It is even possible that the Recent Period in which we live may be itself but an under-
glacial phase, destined to be followed by a return of Glacial conditions in due course,
2 This might account for the different character of the Buckhurst Hill gravel (which is
stated to contain no northern rocks) if we assume that a southern tributary of the ancient
Roding brought down the gravel at Buckhurst Hill, then lying to the south of the latter
river ; but I have no personal acquaintance with the Buckhurst Hill gravel constituents, so
cannot confirm the statement.
3 Mr. Hazzledine Warren has already suggested this in Proc. Geol. Ass. xxi. (1910), p. 454.