204 GEOLOGICAL NOTES.
About 100 yards south of Hatch Lane there were some
curious pipe-like hollows in the surface loam on the western side
of the cutting, the origin of which seems at first sight not easy to
explain. It appears to me that in this matter we shall obtain
light from the appearances presented where the artificial bank
bounding the channel of the present Thames has excluded a
certain portion of the alluvial flat. In the excluded portion we
see river deposits exposed to influences to which they were
everywhere subject before man embanked the stream. In the
surface loam are many irregular hollows, begun as broad surface
cracks and deepened by rain. Similar hollows in old deposits
would become liable in times of flood to be more or less filled
with water bringing with it fine gravel and sand. Probably the
hollows shown in Fig. 2 also owe something to the influence of
Fig. 2. Pipe-like hollows in the loam S. of Hatch Lane.
l = loam. g = gravel.
Height of section about, 11ft. Breadth 22ft.
ice. The kind and amount, however, of the ice-action they
suggest is not that of the Glacial era during the deposition of
the Essex Boulder clay, but rather that of a severe winter of the
present day, such as occurred in 1894-5. Then we saw the
Thames covered with blocks of ice which floated up with the
tide and became stranded here and there during the ebb.
Masses of this kind floating in the more ancient Thames would
not, as now, be confined to its channel, but would often be
deposited, during exceptionally high tides, over the adjacent
alluvial flats. In some cases they would bear with them a
certain amount of sand, gravel or animal remains. And they
would be extremely likely, through the very variable amount of
pressure on the surface loam, caused by their irregularities a -