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190
This uniformity of temperature of deep-well
water is of considerable importance, as the water
remains cool and refreshing in summer, and is less
likely to become frozen in the service-pipes in winter.
The solid matters in the water are almost wholly
composed of mineral substances, which, in the proportion
in which they exist in Metropolitan waters, in
no way diminish the fitness of the water for drinking.
But the salts of lime and magnesia which
constitute the principal part of these mineral
ingredients are objectionable, not only because they
impart to the water what is known as "hardness,"
and thus render it unsuitable for washing, but also
because they cause incrustations and deposits in steam
and kitchen boilers and hot-water pipes.
The saline matters dissolved in the deep-well water
from the chalk is considerably greater in amonnt than
those found in the river water, and inasmuch as this
chalk-water is sent out in its natural condition by the
Kent Company and by the Tottenham Local Board of
Health, these supplies contain more solid matter than
any of the others. The Colne Valley Company, on
the other hand, by treating this chalk-water with
lime before delivery, so reduce the solid matter that
the latter was one-third less than the amount present
in the river waters, and was less than one-half of that
in the deep-well waters either of the Kent Company
or of the Tottenham Local Board of Health.