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known, adverse to riparian sources of supply: wliereas Colonel
Bolton's observations, on the other hand, have reference inter alia
to the condition of the water in bulk at the intakes, and to its
physical qualities when delivered to the consumer—in a word, to
whatever relates to the collection, filtration, storage, and distribution
of the water.
London is mainly supplied from the rivers Thames and Lea, and the New
River ; but a considerable and increasing quantity of water is obtained from deep
wells sunk in the chalk, not only by the Companies which obtain their entire
supply from that source, but also by some of the old Companies, which thus
supplement their intake of river water. The average daily volume supplied per
head of population in 1881 was nearly 33 gallons. This is greatly in excess of
what is required, and indicates waste.
Dr. Frankland is as emphatic as ever in his commendation of "deep well
water," and takes it as the standard of purity in comparative observations on the
waters generally. In a previous report he described it as being "delicious and
wholesome," and uniformly excellent for dietetic purposes; maintaining that in
the interests of temperance and public health it should, as soon as possible, be
substituted for that portion of the Metropolitan supply which is drawn from
polluted rivers. This "pure spring water," he said, is "everywhere abundant
in the Thames 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 even a small 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
'Clark's process,"—the addition of slaked lime, a process equally applicable to
all waters supplied to the Metropolis.
The "hardness" of water represents the weight of carbonate of lime, or its
equivalent 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
19°.8; of the Kent Company's water 28°.3; and of the Colne Valley Company's
water only 60.2. "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
suitable for "washing" delivered in London during the past year was that
of the Colne Valley Company, which was softened by Clark's process before
distribution.
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