THE NEW RAILWAY BETWEEN UPMINSTER AND ROMFORD. 3
during many ages been occupied in deepening its valley, and in
gradually taking a more southerly channel. This last-named
tendency of the Thames is still more obvious between London and
Windsor, in the still greater breadth there of the gravel plain on the
northern bank of the present stream.
The embankment mentioned as existing on the railway between
Cranham Hall and Upminster rests on London Clay. Between
Cranham Hall and the Mardyke (as already observed) the line
traverses a continuous gravelly or loamy plateau; but from Cranham
Hall to Romford the gravel or loam covering the flat-topped higher
ground is cut through, and the London Clay exposed, in the valleys
of the Ingrebourne and other streams which intersect the route.
In the cutting at and west of Upminster Station, London Clay
was seen capped by a variable amount of gravel and loam. These
surface deposits were seldom more than six to seven feet thick, their
base being from eighty-five to ninety feet, and the surface from
ninety to a little over 100 feet above Ordnance Datum. The
gravel hence to Romford belongs entirely to this highest and
oldest of the terraces of the Thames valley in this district. It was
noticeable that in this cutting it was often seen to lie in festoon-like
hollows on the surface of the London Clay, which sometimes even
formed the surface for a few feet between two of these festoons.
This mode of deposition is usually observed to be a characteristic of
these old river-gravels at all levels, wherever the junction with the
London Clay is clearly visible for any distance.
Crossing the Ingrebourne, we enter another cutting, the most
interesting and important along the whole line from Grays to Rom-
ford, though it has now been for some months sloped and soiled, and
yields no sign of its former attractions. About 250 yards east of the
church at Hornchurch the road to Upminster is crossed by others
ranging north and south. About 400 yards north of this point of
junction is the cutting, extending mainly westward, and having a
total length of about 600 yards. Towards its two ends, only London
Clay capped by sand and gravel could be seen; but in the centre,
where the cutting attains a depth of from twenty to twenty-five feet,
a considerable mass of Boulder Clay was once visible, lying in a
hollow on the surface of the London Clay. It extended along the
cutting for a distance of 300 yards, and was in every respect typical
Chalky Boulder Clay. Indeed, when I read a short paper before
the Geological Society on these sections between Upminster and
B 2