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I am indebted to Professor Frankland for the information upon
which the following observations relative to the water supply of
London is founded.
It appears that the purest source is that of the Kent Company.
This deep well water maintains an almost uniform temperature
throughout the year, and having undergone natural filtration
before its delivery, is uniformly clear and transparent. Taking
the water of this Company, therefore, for a standard of comparison,
as unity, the following table will exhibit the average proportion of
organic impurity in the remaining seven Metropolitan Companies,
whose sources are the Thames and the Lea, viz.:—
Kent 1.0
New River 1.5
East London 2.7
West Middlesex 3.0
Southwark 3.3
Grand Junction 3.3
Lambeth 3.4
Chelsea 3.7
Notwithstanding this result, so unfavorable to the Thames and
the Lea, it must be observed that these rivers are as pure at their
source as the wells of Kent, but become contaminated by the
sewerage and washings of cultivated lands on their downward
course. As Professor Frankland pertinently remarks—"This impurity
is composed of a great many substances, some of which are
organic and very objectionable, and at times eminently noxious,
and others are entirely or comparatively harmless." The pollutions
of the Thames and the Lea are very largely of animal origin; and
by the application of the microscope to the sediment deposited by
turbid water, out of twelve examinations during the year 1874,
living and moving organisms were observed in the Southwark
Company's water five times, and in that of the Lambeth Company
four.
The water of the Thames has undergone but slight deterioration
during the year, and it may be hoped that tho progressive increase
of impurity, which occurred in the three preceding years, is now
effectually checked. This is undoubtedly attributable to an improved
sewerage, and proves that much may yet be done still
further to purify the water supplies.
But the mode of receiving the supplies is of almost equal importance
in a sanitary point of view, as the purity of the water
when delivered from the mains. An examination of the tanks and
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