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33
pure water of the Kent Company, derived from the chalk, being
taken as unity.
Maximum. Minimum. Average.
Kent 1. 1. 1.
West Middlesex 7.4 2.0 3.5
Grand Junction 8.5 1.8 3.8
Chelsea 8.1 2.1 4.0
Dr. Frankland states that the Thames, at its chief sources, is as
free from organic pollution as the deep well water from the chalk,
but on its way to the intakes of the Companies it is largely contaminated
by sewage and the drainage from fields dressed with
animal manure, and this especially in the winter months. With
regard to the pollution due to sewage that may be expected
to decline from year to year, as the Thames Conservancy Commissioners
interfere to prevent Towns from making use of the
river for draining purposes; the other kind of pollution will
necessarily be always present. The hardness of Thames water
last year was 21 degrees or parts in 100,000, that is to say it
contained 21 parts by weight of carbonate of lime, or other
equivalent soap-destroying substances in 100,000 parts of water.
"The use of these waters (i.e. of the Thames and the Lea) for
washing, entails a yearly loss of vast quantities of soap or soda
necessary to soften them before they can be used, but any of them
could be softened to nearly the necessary extent by the use of
lime an operation Avhich is employed at Aylesbury, Canterbury,
Caterham, and Tring, to soften similar waters before they
are distributed to the public." The temperature of the water
varied from 36°1 Fahrenheit, in February, to 70°3 in July—a
range of 34°3, whereas the range of the deep well water of the'
Kent Company, was only 4°3 F., viz. from 53°8 to 58°1.
Practically this latter water is unaffected by variation of season, a
point of no mean importance, as the water is less liable to freeze
in winter and does not attain an unpleasant temperature or
mawkish taste in summer. It is worthy of notice that Diarrhoea
—essentially a summer disease—becomes fatally prevalent in
London when the Thames water reaches a temperature of 60°.8 F.
Water may become a cause of disease in two ways, which cannot
be too often mentioned, namely: 1, by retention in dirty cisterns;
and 2, by contamination from drainage. With regard to the
former, it is simply astonishing to see the dirty and disgusting
condition in Avhich cisterns are allowed to become and remain. It
would appear not to be known, or to be generally forgotten, that
the cisterns in which potable Avater is stored require frequent
cleansing. It must be admitted, however, that some excuse for
the neglect of them is often to be found in their faulty position,
an evil which the Water Companies might diminish, and in future
prevent, if so minded, under the " Regulations." In the majority
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