ALLUVIAL AND OTHER RECENT DEPOSITS AT FELSTEAD. 57
In contemplating the origin of this alluvium, we are led back
to a time when the valleys were being eroded through the gravels
and Boulder-Clay of Glacial origin which form the surface of the
district. We are justified, too, when examining these Glacial beds, in
making surmises as to the previous contour of the country, and as
to the immense length of time which has elapsed since the epoch
of their deposition. We know, for instance, that the Glacial gravels
were sometimes formed on sloping surfaces, for at North End there
is a gravel-pit where the stones lie with their long diameters parallel
to the slope; again, on the Stebbing road section near the Broadway,
the same state of the gravel obtains.
All these Glacial deposits are, in Essex, destitute of organic remains,
that is to say remains of a contemporary fauna or flora, and the previous
erosion was eminently destructive—a very significant circumstance
to take into consideration when we speak of the time which has since
elapsed, and equally significant in speaking of the interval between
the deposition of the Glacial beds, and the first evidences of a return-
ing fauna—the shells of the alluvium.
In order to conceive of the beginning of the river alluvium, we
must try to get an idea of the course of the stream along the valley
through this Glacial rubbish. It would appear that the conditions at
first, and for a long time, were unfavourable to the deposition of allu-
vium. The gravels, where reaching the surface, were permeable,
and the Boulder-Clay was planed off with uniform descent seaward,
offering no check to the drainage, nor would there be much vegetation
for a long time to hamper the progress of the water from the first
moment of its journey—the tiny runlet—to its final outfall into the
sea.
The next stage is that in which the gravels, laid bare here and there,
became impervious by saturation and were eroded more rapidly than
the clay : we should then have the conditions under which the allu-
vium was formed, that is of lakelets all along the valley. We are
pretty sure that the alluvium was deposited in still water because of
the fineness of the ingredients of which the clay is composed—being
the last residues of muddy water thrown down. With the exception
of the plants and animals that came upon the scene and played a
subordinate part in its formation, there does not appear to have
been much to cause change in the growth of the deposit down to the
time when man interfered and laid it dry. The rains and floods
smoothed the sides of the valleys, took off the tops of the hills, and
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