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basin: in dry seasons it constitutes the sole supply of the Thames and
the Lea, and even after the most protracted drought, more than
350,000,000 gallons of it daily flow over the weir at Teddington,
whilst a further very large volume of it joins the Thames lower down."
At present the inhabitants of the Metropolis, generally, can only use it
after it has been mixed with the excrements of a large population,
and used for the washing of vast quantities of filthy rags in paper
mills, and of linen in laundries. It would be a most valuable boon
to London, he thinks, if ever so small a fraction of this prodigal supply
could be collected, preserved from irremediable pollution, and distributed
to those portions of the Metropolis which are not at present
supplied with such water. The principal objection to it is its hardness,
but this is an objection easily surmounted, by "Clarke's process"—the
addition of slaked lime.
The "hardness" of water represents the weight of carbonate of
lime, or its equivaleat of other soap-destroying substances, found in
100,000 parts of water. The average hardness of the Thames water
delivered in London last year was 2008; of the Kent Company's
water 2804; and of the Colne Valley Company's water only 6o3.
"All hard water must be softened before it can be used for washing
linen : when it is softened in detail by the laundress, the operation
costs, for an equal volume of water, at least eighty times as much (in
soap and soda) as it costs when conducted on a large scale by a water
company. The only water fit for "washing" delivered in London
during the past year was that of the Colne Valley Company, which was
softened before distribution by the process above-mentioned.
All waters, save artificially prepared distilled water, contain more
or less "solid matter." The solid matter in river water is composed
of a variety of substances, by far the largest proportion being entirely
harmless when the water is used for dietetic purposes, but injurious
when it is used for washing, because the water is thereby rendered
hard ; but a small proportion consists of organic substances, which
are always objectionable, and at times are dangerous to health. The
average proportion of total solid matter was much higher in 1879
than in 1878 : the proportion in 1878, moreover, having been greater
than in the previous year. The deep-well waters delivered by the
Kent Company and by the Tottenham Board of Health contained
the largest proportions of these matters, but the deep-well water
GG