154 THE ESSEX NATURALIST.
floods on the marsh were so great that the ends of Lea Bridge
had to become temporary tram termini with an emergency
cart ferry between.
On the other hand, the marshes have been used to great
advantage. Out of the alluvium the docks and navigation
channels were dug. The isolation afforded by the marsh made
it a safe place for unhealthy and dangerous works—sewage
farms, munition, chemical and electrical works. In this way,
factories grew up below the 50 feet contour line.
The most recent factories owe their existence to modern
communications and modern needs. Engineering works are
common, flour mills, breweries and malt-food works are found
at good collecting centres, such as Ware and Stratford. In the
Lower Valley malthouses and breweries are disappearing, owing
to the pollution of the water. The factories and works increase
in number in the south, the fields decrease and finally disappear,
replaced by refuse dumps filling up the marsh where skating was
indulged in 40 years ago.
From the standpoint of modern industrialism many of the
assets of a "highly productive" area are absent. The Lea
Valley contains no coal or iron, no oil or great waterfall. Yet it
has what many other areas have not, natural features which
contributed to make it an active and important part of the great
metropolitan area.
WATER TURNED TO "BLOOD" IN AN
EPPING FOREST POND
BY D. J. SCOURFIELD, I.S.O., F.Z.S., F.R.M.S.
(With 1 Text Figure.)
ON the 14th September, 1924, a very striking phenomenon
was seen in the little pond with alders round it, on Fair-
mead Bottom, near where Fairmead Lodge used to stand. One
end of the pond (the southern) was of a most vivid red-purple
colour, looking not like water at all, but like liquid paint very
nearly the colour of blood. The whole of the water at that
end was coloured in this way, but the intensity of the colour
died away towards the middle of the pond. The other half of
the pond was covered with duckweed.