NOTES ON ESSEX GEOLOGY.
269
"What appears to happen is, that successive stages . . overlap
each other as they are followed northward. At the southern
extremity of the area, at Walton, we find the oldest Red Crag,
a deposit yielding a fauna closely allied to [that of] the Coralline
Crag. A few miles northward this is lost," in Suffolk.
1891.
H. W. Monckton and R. S. Herries described Hill Gravels north
of the Thames7 and largely in Essex. They describe (pp. 109-
111) sections at Billericay (chiefly of flint-pebbles), Norton Heath
(to a great extent of flint-pebbles), and the Epping Hills. They
criticise some of Prestwich's views.
1892.
In this year our Past President, T. V. Holmes, contributed
a paper on the railway from Grays to Romford, which is of im-
portance to Essex geologists,8 because it records the presence
of Boulder Clay in the Hornchurch cutting, in a slight hollow
of London Clay and overlain by gravel, which spreads over
it on to the London Clay, at either end. The gravel belongs
to the highest terrace of the old Thames Gravel, that often
described as the 100 foot terrace, and were it not for this cutting
the existence of Boulder Clay beneath the gravel would not have
been seen.
I visited the section when it was clear and not overgrown,
and I want no better evidence that the highest and oldest terrace-
gravel of the Thames Valley is newer than the Boulder Clay,
a conclusion inferred only beforehand.
It follows therefore, that the erosion of the valley is Post
Glacial, to a large extent at all events.
1894.
T. V. Holmes supplemented his paper of 1892 with
notes on the railway from Romford to Upminster9 and
described the Romford cutting as showing at one part a slight
hollow of silt with sand and pebbles, between the gravel and the
London Clay. This material seemed "to be a fragment
7 Proc. Geol. Assoc. Vol. xii., pt. 4, p. 108, etc.
8 Quart. Journ. Geol. Soc., Vol. xlviii., pp. 365-372.
9 Quart. Journ. Geol. Soc. Vol., 1 , pp. 443-452, 460-462.