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182
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 amount 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 Lacal
Board of Health, these supplies contain, in two
out of the three cases, 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 reduced 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.
The comparatively small proportion of organic
material which the solid matter invariably contains
is, on the other hand, of the greatest
importance in connexion with the use of the
water for drinking purposes. For although the
actual amount of this organic matter is often quite
insignificant, yet it may be of the most objectionable
character on account of its origin. Thus the
water, both of the Thames and the Lea, receives,
above the points where it is abstracted for the purposes
of the Metropolitan supply, various contributions of
organic matter of animal origin, such as the drainage