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sewage must not infrequently contain the excremental matter of
persons suffering from typhoid fever and may not improbably
in the future contain from time to time the excreta of persons
suffering from cholera. The virus of both these diseases has
been found by past experience to have been disseminated by
water and to have produced fatal results in persons drinking
such water.
" Not only are these diseases known to be waterborne, but
experience has shown that a very small amount of the excremental
matter of persons suffering from them is capable under
favourable circumstances of infecting vast volumes of water."
Insufficiency of Natural Purification.
After describing the various circumstances which are shown
by the Commission to contribute to the purification of the
rivers, Mr. Murphy says: " The fact may be accepted that
these powers exist and are operating in the Thames and Lea to
an extent which contributes in no small degree to the safety of
the London water consumer." Yet the Commission evidently
does not look upon these natural processes as in themselves
sufficient to render the water fit for domestic purposes, but is
only satisfied in such agencies and the operations of the water
companies combined, suffice to ensure that wholesome water is
supplied to the consumer.
As it is probable that the completeness of the future operations
of the water companies may depend upon the necessity
which can be shown for efficient filtration, it is a matter of great
importance that the natural processes of purification should not
be held to be more deserving of confidence than they really are.
After a careful study of the statements in the Commission's
report, Mr. Murphy is led to think that some of the reasons
given for assuming that the London population is not exposed
to risk are less deserving of acceptance than appears at first
sight.