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189
and is less likely to become frozen in the service pipes in
winter; whilst river water at 68.0° is unpleasantly vapid, and
at 37.6° is soon cooled to the freezing-point." Dr. Frankland
refers to the hardness of the waters, due to the salts of lime
and magnesia—mainly bicarbonate of lime—"which in no way
diminish the fitness of the water for drinking," but make it
unsuitable for washing, and also cause incrustations and deposits
in steam and kitchen boilers and hot water pipes. The
hardness can be largely reduced by Clark's softening process.
By the adoption of this process, which consists in treating the
water with lime, the initial hardness of the Colne Valley Company's
chalk water, which is much in excess of that of Thames
water, is reduced to about a third of the hardness of river
water. The usual reference is made to the possible danger to
health resulting from the small amount of organic animal matter
found in the water, as this may be accompanied by zymotic
poisons: but "the chances of such substances reaching the
water consumers are enormously reduced, both by the care
which is exercised in excluding the flood waters from the
reservoirs, and especially by the efficient filtration to which
the water is subjected before distribution." Still, " there is no
absolute guarantee that the noxious ingredients, which may at
any time be present, are wholly removed." It is only fair to
add that there is no evidence of injury to health resulting
from the use of the water. The discharge of untreated Town
sewage into the Thames has been almost completely stopped.
Most of the Companies, moreover, are endeavouring to substitute,
as far as possible, water from subterranean sources for
raw river water. Figures are given to show that in respect
of "organic impurity," the Thames water distributed during
the year 1892 was of much better average quality than that
distributed in 1891.
Bacteriological Examination.—Dr. Frankland gives
the results of his bacteriological investigation of the waters by
Koch's gelatine-plate culture, showing an enormous reduction