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rendered hard "by the presence of these matters, it is
decidedly injurious when used for washing.
A small proportion consisted of organic substances,
always objectionable, and at times, when present in river
water, dangerous to health.
The pollution of the Thames and Lea is to a great
extent of animal origin. The deep-well water supplied
by the Kent Company is unaffected by animal or
vegetable life. The natural filtration which the Kent
Colne Valley and Tottenham deep well waters undergo
through an enormous thickness of chalk, renders artificial
filtration unnecessary, and is the cause of their almost
uniform clearness and transparency.
It is admitted that, during the past ten years, there
has been a diminution of organic impurity in Thames
water delivered in London. That this improvement
is owing to the more careful treatment of the water by
the Companies is shown by the fact that, in the water
supplied and inefficiently treated by the Southwark
Company during a great part of the year 1877, the
proportion of organic impurity was excessive. There
is no abatement, however, of the evidence of previous
sewage contamination in the Thames and Lea waters :
hence the likelihood of morbific matter derived from
animal excreta being distributed to the customers of
the respective companies drawing their water from
those sources.
The opinion of the late River Commissioners, in
their Report on the Domestic Water Supply of Great
Britain deserves consideration. " We consider that