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storage.—The number of days' supply represented by
the capacity of the subsiding reservoirs, for storing unfiltered
water, belonging to each of the local companies, was as follows :
Chelsea 14.7, Ws est Middlesex 6.7, Grand Junction 3.5. The
East London Company now heads the list having storage
equal to a supply for 15.1 days. It should be stated that
the Grand Junction Company have the means, during floods,
of pumping from the gravel beds adjoining the Thames, and
this is practically equivalent to an addition to their storage
resources.
Filtration.— Provision was made by the Metropolis
Water Act, 1852, (sec. 4), for the efficient filtration of the water
before distribution. Testimony is uniform that this provision
is duly carried into effect. The late Sir Francis Bolton, the first
Water Examiner appointed under the Water Act of 1871,
laid down the conditions necessary to secure this object; viz.
(1) Storage in subsiding reservoirs of capacity sufficient to
avoid the necessity of intake of flood waters ; (2) a sufficient
area of properly constructed filter beds ; and (3) the limitation
of filtration to a certain speed, represented by the
passage of about 540 gallons per square yard of filtering area
in 24 hours, or 2½ gallons through each square foot of surface
per hour. These conditions, as we have seen, are complied
with by the several companies. Whatever the condition of
the water when taken from the river, or passed on to the
filtering beds, the filtered water as delivered to consumers is
uniformly bright and clear. In former reports I have fully
described the mode and apparatus of filtration, and to those
reports I may refer for detailed information on the subject.
Deterioration of Water in Dirty Cisterns.—It
need hardly be said that filtration, however perfect, avails
little, if the water is allowed, as frequently happens, to be
fouled after delivery. The attention of householders cannot,
therefore, be too frequently drawn to the necessity for the