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8
REPORT ON THE RESULTS OF THE ANALYSIS OF SAMPLES OF WATER FROM
WATERCRESS BEDS IN AND AROUND THE COUNTY OF LONDON.
By Dk. Frank Clowes, Chemist to thk London County Council.
In accordance with the order of the Committee, samples of water from the watercress beds in
and around the County of London have been collected under the supervision of the Medical Officer of
Health, and forwarded to me for analysis.
Between 6th May and 27th August, one hundred and twenty-nine samples have been received.
These have been submitted to chemical, microscopical and physical examination.
The results obtained are stated in grains per gallon and are set out in the table* accompanying
this report, together with the dates, times and places of collection.
They include the amounts of albuminoid ammonia, which is a measure of the nitrogenous
organic matter present in the water ; and the oxygen absorbed in 4 hours, which is a measure of the total
organic matter.
For convenience of comparison, I have grouped the results as follows:—
Group "A," including 53 samples, in which the nitrogenous organic matter present was
about the same as the nitrogenous organic matter present in the Thames-derived filtered water
as supplied to the County of London.
Group "B," including 47 samples, in which the nitrogenous organic matter present was
about the same in quantity as that present in the water of the river Thames at Hampton and
Sunbury, above the intakes of the various district works supplying London.
Group "C," including 22 samples, in which the nitrogenous organic matter was large in
quantity.
Group "D," including 7 samples, in which the nitrogenous organic matter was very large
in quantity.
With a few exceptions, the samples in Groups "A" and "B" may be considered fairly satisfactory
in chemical character. The microscopical examination of some of the samples showed, however,
the presence of matter of an undesirable character.
The samples in Group "C" contained a large quantity of nitrogenous organic matter, and in four
of them a slight odour of sewage was detected when they were heated to 100 deg. F. From the
results of my examination I am of opinion that some of the samples in this group were contaminated
with sewage matter.
The samples in Group "D" were organically of very bad quality, and six of them were, in my
opinion, undoubtedly polluted with sewage.
All the samples in Group "D," except No. 3, gave a distinct odour of sewage when they were
heated to 100 deg. F.
Frank Clowes,
Chemist.
*It lias been thought unnecessary to publish this table, inasmuch as the classification by the Chemist of the
waters examined into four groups is sufficient for the purposes of this report.