WANSTEAD AND WALTHAMSTOW, ESSEX. 117
Large flints, very little waterworn, from the Chalk.
Cherty looking stone, perhaps carboniferous.
Red very hard sandstone, and brown and grey sandstones.
Brown quartzite boulders—common.
Purplish-grey quartzite, somewhat glassy.
Large quartz pebbles or boulders, one measured 3 x 11/2 x 11/2
inches.
Conglomerate or coarse grit of quartz and felspar.
One pebble which I think is an igneous rock.
The Barking Side patch of gravel is one of several at about 100
feet level. It may well be of much the same age as the gravel at
Hornchurch, which Mr. T. V. Holmes has described as overlying
Boulder Clay (Essex Nat. vii., pp. 1-14). Below these gravel
patches we find the great spread of Thames Gravel which underlies
the brickearth, in which mammalian remains and shells have been
found. One cannot depend on slight differences of altitude as a
conclusive test of the age of river gravels, for a river will often cut a
channel and then fill it up again to a greater or less extent. Thus
at Dartford we find a great thickness of gravel underlying the gravel
of Dartford Heath. A magnificent section showing this was recently
visited by the Geologists' Association, but as I hope that Mr. F. C. J.
Spurrell will soon publish a full account of it, I refrain from entering
on any details now. Mr. B. B. Woodward has also pointed out that
under certain circumstances the gravel at higher levels may be newer
than the gravel at lower levels in a valley.2 In the west Essex part
of the Thames Valley, however, I am inclined to believe that the
succession of the Drift formations is as follows, beginning with the
oldest:—
1. The Pebbly Gravels of the Epping Ridge and Lam-
bourne End.
2. The Gravel of Buckhurst Hill; a few patches of gravel
near Loughton.
3. The Chalky Boulder-Clay.
4. The Gravel of Hornchurch overlying the Chalky Boulder-
Clay and the gravels at about 100 feet O.D. of Rom-
ford and Barking Side.
5. The great sheet of gravel at Barking, Ilford, and Wal-
thamstow, which is for the most part below 50 feet
O.D.
6. The brickearth of Ilford, with mammalian remains, etc.3
2 Proc. Geol. Assoc. 1889-90, vol. xi., p. 386.
3 See on this question T. V. Holmes, 1893, Essex Nat., vol. vii. p. 1.