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On the other hand, in the summer months, the water
attained a greater degree of purity than ever before observed ;
the excessive drought prevented much animal matter, both
solid and liquid, from reaching the streams. The refuse was
absorbed into the thirsty soil, whence it was afterwards partially
dislodged by the heavy rains of October and December.
It has been frequently asserted, but without proof, that the
noxious organic matter of sewage, when discharged into a
river of considerable magnitude, is entirely destroyed by
oxidation after a flow of a few miles
Tliis assertion is erroneous. In his evidence before the
Rivers Pollution Commission, Sir Benjamin Brodie says,—
I should say that it was simply impossible, that the oxidizing
power acting upon sewage running in mixture with
water over a distance of any length is sufficient to destroy its
noxious quality. I believe that an infinitisimally small
quantity of decaying matter is able to produce an injurious
effect upon health.
Dr. Frankland calls attention to the very inefficient filtration
of a considerable proportion of the water supplied to the
metropolis, and says that (amongst others) the water of the
Lambeth Company was occasionally in such a muddy condition
as to render it totally unfit for domestic use. This state of the
water was observed after heavy rainfall in this district, and the
Company were communicated with upon the subject.
That this muddy state of the water was unnecessary, may
be derived from the fact that the West Middlesex Company,
which draws its supply from the Thames, did not fail upon
any occasion to send out the water clear and transparent.
During the year the Kent Company's water exhibited tor
a time an exceptionably high state of contamination.
In February it contained no less than 59.2 parts ot solid
impurity in 100,000 parts. Of the above 59 2 parts 14.7
were common salt, the occurrence of which in such quantities
it is difficult to account for, without assuming contamination
from a tidal river. In March the condition of things was
worse, for the solid impurity had increased to 70.2 parts an
the common salt to 23.7 parts.