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sources of water-supply, and some of them have already completed
works for utilizing underground waters which have undergone natural
filtration through great, thicknesses of gravel and sand, whilst othersare
sinking deep-wells in the chalk. Last year it had to be remarked
that the protection provided by the common law to rivers was denied
to subterranean sources of water, which, it appeared, as the result of a
decision by Mr. Justice Pearson in an important case, (Ballard v.
Tomlinson), might be polluted or poisoned to an unlimited extent
without legal redress. It is satisfactory, in the interests of public
health, that this judgment has since been unanimously reversed in the
Court of Appeal.
A marked and undeniable advantage of spring water is its evenness of temperature.
The mean temperature of all the Companies' waters is
practically the same, but the extremes are much more marked in the
case of the river than in that of the deep-well waters. The range of
temperature in the water of the Thames, as delivered by five of the
Companies last year, amounted to 29°.7 Fahr., viz., from 42°.8 in December
to 72°.5 in August. The deep-well water furnished by the Kent
Company varied in temperature from 53°.6 in February and March to
to 58°'8 in June; range 5°.2. The deep-well waters remain of an
agreeable coolness in the hottest months, whilst the river water becomes
unpleasantly warm and unpalatable.
The transparency or otherwise of water is ascertained by its appearance in
a tube two feet in length, and is expressed in arbitrary terms settled
by common agreement, as in the following table, which shows the
degree of efficiency of filtration of Thames water as supplied by the
Companies in this parish, and indicates a great improvement over

"There is nothing which exhibits more strikingly the greatly increased
care and attention which is bestowed upon the water supply of the
Metropolis, by the various companies to whom this supply is entrusted,
than the marked improvement in transparency. For the turbidity of
the water is the only factor over which they have complete control,
depending, as it does, exclusively, upon the storage capacity and
filtering appliances which each water company has at its disposal."
The deep-well waters are uniformly bright, and require no artificial
filtration.