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LATER TERTIARY GEOLOGY OF EAST ANGELA.
Ill
responds with the level at which the clay was reached in the well
at the railway-station, it seems to us that this bed of chalky clay
and overlying brick-earth may probably be similar to that occurring
in the Yare valley, marked a in Sections V. and VI., and of inter-
glacial age ; and if so, the beds at Copford, from which the late
Mr. John Brown obtained an extensive collection of the remains of
Vertebrata and of land and freshwater Mollusca, may possibly be of
similar age. We are informed by Mr. Whitaker that the pits at
ApixLeford Bridge were closed when the members of the Geological
Survey examined the district, but that they found brick-earth in the
same part of the valley, not far off, which yielded remains of fresh-
water Mollusca, and which they regarded as of Postglacial age. In
the face of this we feel more hesitation than we otherwise should in
identifying the bed at Appleford Bridge with that in the Yare
valley ; for the evidence available to guide us to an opinion as to its
precise age (whatever we regard that as being) is, it must be con-
fessed, obscure. Section XXIII. represents the appearance presented
by the section when we examined it.
Fig. 24. — Section XXIII., at Appleford Bridge, near Witham.
a. Blue Clay with rolled Chalk, identical in appearance with the Upper
Glacial of the neighbourhood.
b. Sandy Brick-earth passing down imperceptibly into a.
c. Red sandy gravel passing downwards into yellow sand.
d. Gravelly wash and humus. e. Water. /. Talus &c.
It was pointed out by one of us * that the highest elevation to
which the Middle Glacial attained in East Anglia was about 360 feet,
at Danbury in Essex, the usual limit being between 200 and 250
feet, the Upper Glacial overlapping it above these elevations and
resting on the older formation direct ; and in Middlesex, at Einchley,
it underlies the Upper Glacial at an elevation somewhat exceeding
300 feet. Mr. Penning f has made this limit in elevation and this
overlap the basis of an argument to prove that the submergence
was, during the deposit of the Middle Glacial, confined to something
like the altitude to which this formation ranges. The not unfre-
quent absence of the deposit, however, at low elevations within the
area over which it usually occurs, and its absence over a wide area,
embracing most of the counties of Cambridge, Lincoln, Northampton,
Leicester, Rutland, Huntingdon, and Bedford, at elevations far below

• Geol. Mag. Feb. 1870.