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170
which the river water has now exhibited for several years past,
was maintained in 1888. The monthly variation in the temperature
of the water is very great (viz., from 37°.4 Fahr. in
February to 65°.3 in June = 27°.9), that of the Kent Company's
deep well water being 2°.7 only, viz., from 53°.6 in February to
56°.3 in August This water thus remains cool and refreshing
in summer and is less likely to become frozen in the servicepipes
in winter. The river water is soft by comparison with
the deep well water, which owes its hardness to the much larger
proportion of mineral substances which it contains and which
compose the great bulk of the "solid matters." The hardness
of the water, sufficiently great to materially diminish its value
for washing, steam, and industrial purposes generally, is almost
entirely due to the presence of bi-carhonate of lime in solution ;
this bi-carbonate of lime can be readily removed by treating the
water with lime, as is so successfully done by the Colne Valley
Company; by which the hardness of that Company's water is
reduced to from one-fourth to one-fifth of its original amountin
1888 from 30°.2 to 7°.5; the hardness of the Thames water
being 20O-0. This mode of softening is by far the most economical,
for it entails only about one-eightieth of the expense which
devolves upon the private consumer in the shape of additional
soap required for washing purposes. The small proportion of
organic material which the solid matters contain, is of the
greatest importance in connection with the use of the water for
drinking purposes; as it may be of the most objectionable
character on account of its origin—such as the drainage from
manured land, the effluents from sewage works, or even raw
sewage itself. The animal matter may at times be accompanied
by zymotic poisons dangerous to health—although
the chances of such substances reaching the consumer are
reduced by filtration and by the exclusion of flood waters from the
reservoirs. During the greater part of the year the water contained
only a very moderate amount of organic matter; but the
amount was exceptionally high in the months of March,
November, and December. The water sent out by the West