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155
waters during 1889, includes also the results of similar
examinations of the water supplied by the. Colne
Valley Water Company and the Tottenham Local
Board of Health. He states that the weather during:
the past year has been on the whole favourable for the
operation of those Companies which derive their
supplies from rivers, and as the increased efficiency of
subsidence and filtration observed for several years
past has been fully maintained, the water delivered by
these Companies has been, on the average, of even
better quality than that delivered during the year
1888.
Temperature: Whilst the monthly variation in
temperature in the case of the river waters is very
great, the temperature of the deep-well water is practically
constant throughout the year. Thus the water
principally derived from the Thames and supplied by
the Chelsea, West Middlesex, Southwark, Grand
Junction, and Lambeth Companies, varied in temperature
from 70.2 Fahr. in July to 37.8 Fahr. in
December, and the water from the Lea distributed by
the New River and East London Companies fluctuated
from 68.9 in July to 39° Fahr. in December. On
the other hand, the temperature of the deep-well
water delivered by the Kent Company varied only
between 55.4 Fahr. in July to 510l Fahr. in
February.
This great uniformity in temperature of deep-well
water is of considerable importance, as the water