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THE ESSEX NATURALIST
up, so that navigation in the middle reaches had to be suspended
for several weeks.
In the case of the River Lee, and similar southern streams nor-
mally fed by springs and by tributaries running over the chalk, the
flow has lessened in historic times, and particularly in recent times.
It is held by some geologists that these streams were larger, and
broke surface farther upstream than they have normally done
recently. This may be in part due to a smaller annual rainfall, and
in part to the deforestation of the uplands and draining of the
valleys. Be that as it may, there is no doubt that the large-scale
modern deep-well and bore-hole pumping is seriously lowering
the water level in the chalk and ballast of the London Basin, so
that springs have failed and streams have sunk into their porous
beds where formerly water rose to the surface. The general water
level is falling, as more is being abstracted than is being made up
by rainfall and ground absorption.
DISPOSAL OF SEWERAGE AND TRADE EFFLUENTS. POLLUTION
As a general rule the public of this country have taken little
interest in the condition of rivers, and have been well content to
treat them as open sewers. The condition of the River Fleet prior
to its being covered-in evoked much adverse comment. But it is
not only sewage as such that does harm. A river has remarkable
recuperative powers, provided there is sufficient water and oxygen
dissolved therein to treat any incoming sewage or similar matter;
and, when modern plant is installed for the purification of such
liquors, the condition of the river need not be impaired. No resi-
dent of London need be apprehensive because the large towns of
Oxford and Reading discharge their sewage into the Thames.
Modern treatment is able to deal with such organic impurities. It
is, on the other hand, the inorganic trade wastes, in many cases
actual poisons, which do most to pollute the streams into which
they are allowed to flow. Many Pennine streams, clear and spark-
ling at their source, have been utterly fouled by the industrial
waste waters that have flowed into them. No weed grows in them;
no fish or other life can survive in them. In southern England, cer-
tain industrial establishments have been permitted to continue to
poison rivers, no adequate powers having existed to control them;
but it is intended that the powers of prevention of pollution that
will be given to the forthcoming River Boards will be used to
eliminate such cases where possible. At one time, the beet sugar
factories discharged an effluent that gave rise to an injurious
fungus along the river below the outlet, but improved treatment of
the effluent has removed this nuisance.
In the West Riding of Yorkshire a Rivers Board was set up
some years ago to combat the nuisance of general pollution, with