198
THE GEOLOGY OF THE LEA VALLEY.
informed me some time since, that when the brothers Want were
the proprietors of the Broxbourne Fishery some forty years ago,
about 1850, there used to hang in the smoking-room of the inn
there a string of salmon, trout, and pike heads. On their quitting
the place, however, the subsequent proprietor, Mr. Beningfield (who
was a gardener and cared little for fishing), threw them away!
Could they have been preserved to the present day, what in-
teresting relics they would be in the eyes of anglers and
naturalists.
THE GEOLOGY OF THE LEA VALLEY.
By T. V. HOLMES, F.G.S. (Vice-President).
[Read at Meeting on the River Lea, July 14th, 1894]
AT London we are in the midst of a broad synclinal fold or
basin, consisting of Tertiary and later rocks towards its
centre and of Chalk and other Secondary formations towards its
outer rim. The Tertiary area includes the greater part of Essex and
the south-eastern corner of Suffolk, while south of the Thames it
comprises a considerable portion of northern Kent and Surrey.
West of London it becomes gradually narrower and narrower, till
around Marlborough it is represented only by a few scattered out-
liers. Beyond this Tertiary district is one in which the underlying
Chalk is more or less exposed, as at Saffron Walden, Royston,
Hitchin, and Dunstable north of the Thames, and along the North
Downs from Folkestone to Guilford, south of it. As the Chalk dips
northward from its outcrop in Kent and Surrey, and southward in
the counties of Essex,. Cambridge, Bedford, Hertford, and Buck-
ingham, it naturally follows that rain-water sinking into its surface,
or percolating through it from some overlying bed, tends to flow
southward from Essex or Cambridge, and northward from Surrey
and Kent. A few springs are occasionally found at the base of the
Chalk escarpment in certain localities, but in the main the water
flows through the Chalk 1 in the direction of its dip, and issues from
it in springs where the Chalk is so saturated that the saturation-level
is above the local level of the ground. South of the Thames, along
the North Downs, there is a much smaller breadth of bare Chalk 2
than there is from the Chiltern Hills to Essex and Suffolk.
1 See Whitaker, "Geology of London,'' etc., vol. i., pp. 61, 62.
2 Chalk covered only by Glacial Drift is here included.