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CHAPTER XIII.
TABULAR STATEMENTS OF RESULTS OF WATER ANALYSES
AND REMARKS THEREON.
A very few words are still necessary on the results of the analyses of water
samples as a whole. The reader is at this point recommended to glance through Part
II of this report. There will be found the results of three quarterly analyses of each
supply, placed side by side, for reference. It may not be apparent why all these are
included in this report, but as all this work is in its infancy at present, it has been
considered necessary to give all the details on which our conclusions are based. The
method of reading these results will present no difficulty. In giving an opinion we
have avoided making strong statements because it is only quite recently that we have
arrived at conclusions to warrant these. Tables 4 (a), (h) and (c) require explanatory
certain remark.
The water supplies in this Presidency are grouped into three classes according to
the sources whence the water comes. The figures given in these tables are of interest,
the important ones being those relating to the natural or unfiltered water.
Group A.—River waters.
The various organisms present in river waters do not show such great variations
in percentages as is the case with the organisms of other supplies for the simple reason
that pollution is constantly being added. The figures in the third quarter are different
from those of the first two, and show a greater tendency to more even distribution of
the organisms. The reason for this is not known.
The results obtained from the lakes Group B) during the three quarters are made
the subject of a separate chapter (vide Chapter X).
Group C.
In this group there are only three regular supplies. The figures are not sufficiently
large to draw any conclusions from but the following points may be just noticed :-
Prevalence of cloacæ in the first quarter, the rarity of lactis ærogenes in this
quarter ; the great falling off of cloacæ in quarters 2 and 3 ; the increase in bacillus
grunthal and bacillus lactis ærogenes ; the increase in the numbers of coscoroba
during the third quarter.
As regards MacConkey's Groups 1, 2. 3 and 4 it will be observed that in all
natural waters there is some considerable variation. Considering them in the light of
our remarks in Chapter VII on the study of fœces, we are not inclined to place any
importance on the classification of organisms in this way.
If it could be stated that any particular group can be looked upon as more
objectionable than another such a classification might be of value. Group 2 contains
a large number of susceptible and therefore objectionable organisms, but it is not
entirely composed of these susceptible varieties. Further susceptible organisms
also are found in all of the other groups. For purposes of water analysis we do not
consider that this classification tells us anything whatever as regards water-supplies.
Filtered waters.
A reference to table XIII (d) will show how exceedingly defective filter
beds in the Madras Presidency are. We have not got single installation that is really
working properly. This is due to a variety of causes the most important of which are
(1) the unsuitable quality of sand used, (2) from the uneven quality of the water
put on the beds and the careless working of the beds, (3) Leakage in the masonry
structure of the beds. There is no particular necessity to pursue the subject further, as
remedial measures are in progress, but have not yet had time to affect the figures.