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spring's; a fact "which had previously been doubted and even
denied. Chalk spring water is merely softened by this process;
on the other hand, Thames water, which contains a large
proportion of nitrogenous organic matter, derived partly from the
drainage of 800,000 people in the river above the in-take of
the water companies is, by the application to it of Clark's
process, not only rendered as soft, or nearly so, as the chalk
water similarly treated, but a considerable proportion of the
organic matter which it contains in solution is removed by
becoming attached to the precipitate of chalk which is produced
by the addition of slaked lime to the water.
The cost of applying this process to the London Water supply
would be, 14s. 7d. per 1,000,000 gallons. This includes labour,
cost of Lime, and interest on Capital required for reservoirs and
apparatus. Clark's process of softening is only applicable to such
water as owes its hardness entirely or chiefly to t lie Carbonate of
Lime and Magnesia, held in solution by Carbonic Acid. All the
water supplied to London is of this character. The following is
the method of performing the operation upon London Water. To
soften 500 gallons of the water supplied by the Chelsea, West
Middlesex, Southwark, Grand Junction, Lambeth, New River,
or East London Company, slake thoroughly 12oz. of Quick Lime
in a pail-full of water, stir up the Milk of Lime, and pour it immediately
into a Cistern containing at least 30 gallons of the water
to be softened, taking care to leave in the pail any heavy sediment
that may have settled in the bottom in the few seconds that
intervene between the stirring and pouring. Fill the pail again
with water, and stir and pour as before. The remainder of the
500 gallons of water must then be added or allowed to run into
the Cistern from the supply pipe. If the rush of the water thus
added, does not thoroughly mix the contents of the Cistern, this
must be accomplished by stirring with a suitable wooden paddle.
The water will now appear very milky, owing to the precipitation
of the Chalk which it previously held in solution, together
with an equal quantity of Chalk which is formed from the quick
lime added.
After standing for three hours the water will be sufficiently
clear to be used for washing, but to render it transparent enough
for drinking, at least twelve hours settlement is required. It
deserves again to be mentioned that the patent for this valuable
process having expired, the public are now free to use it, but, the
system of intermittent supply, which is still maintained in London,
oppose a serious obstacle to its adoption in private houses, on
account of the necessity of performing the operation in the
few minutes during which the water is daily delivered from the
Companies' mains.
I may here remark, that Section 7 of the Metropolis Water
Act, 1871, enables the Metropolitan Authority,—The Metropolitan
Board of Works, after the expiration of eight months from
the passing of the Act, to require the Water Companies to afford