72 .
•
which are not strictly speaking lake water, and. therefore should not be included • in.
n
also, two or three samples, that are in reality spring . waters, have been
wrongly inserted. The results of the settling tanks from Kurnool and. Cocanadam have
been added to table X (a), they are not found in table XIII (b). Consequently
thefigures given in X (a) are actually more accurate, from the point of view of con-
taming the results of analyses of stored water only, than those given in Chapter XIII.
A comparison between the two sets of figures will show that the difference between
them is not great.
It is necessary to make a few remarks about the meteorological conditions obtaining
in each quarter:—
(1) Quarter ending 30th September 1908.—During these three months no rain
had fallen in any of the towns given in table X (a), for many months prior to
the taking of the samples, with the single exception of Ootacamund. All the storage
reservoirs were extremely low, Adóni, Ootacamund and Vizagapatam were extremely
short of water. Consequently the analyses give the results of waters that have been
exposed to sunlight for a great length of time, in no case less than 6 months.
(2) Quarter ending 31st December 1908.—In practically every town more or less
rain fell during this quarter. In most, particularly at Vellore, Ootacamund, Coonoor,
Madras and. Adóni, extremely .heavy rain fell, the totals being over 30 inches. The.
reservoirs were all of them replenished with water. In the case of Red Hills the
rainfall extended, on and off, for a little over two months. During the year under
report the rains were pretty normal, with the exception of Vizagapatam. Cocanada
had also deficient rain, but in this case the water-supply is not dependent directly on
the monsoon but on the irrigation canal.
(3) Quarter ending 31 st March 1909.—There was very little general rain during
this quarter, but Madras, Ootacamund, Vellore, all received a considerable downpour,
amounting to about 6 inches, within the first week of January 1909. After this
the weather was fine.
-
There is, however, another point which must be mentioned, namely, that quite-
a large number of these reservoirs and lakes have supply channels in the shape of
streams running into them. During the months of January and February these were,
for the most part, discharging.. In March, April or May they usually dry up.
Of course, it is scarcely necessary to state that when rain is not actually
i.n India, the sky is usually cloudless and the days are clear.
Let us now discuss the results of the bacteriological analysis of the water samples
taken during these three quarters.
In the quarter ending 30th September 1908 it has already been stated that the
lakes were extremely low. Therefore it may be assumed that the organisms present
really represent those particular varieties, which have succeeded in surviving during
the hot and sunny months of the Indian spring and summer, a period of from 6 to 9
months.
A reference to table X (a). shows that fœcal organisms were relatively extremely
common in the water of these lakes (as the figures in the narrow column demon-
strate) ; there is only one sample in the whole number that gives no fecal bacilli in
5 cc., viz., Tiger Hill in Ootacamund; in all the others fœal bacilli are present
in 1 cc.,.1 cc. or .01 cc.
In spite of the great power of the sun during the summer months, these organisms -
that are present, have not been affected to any great extent, otherwise the water
would be purer. Consequently it is certain that the organisms found at this time are
indeed resistant ones. Both tables X (a) and X (b) demonstrate the fact that 75
per cent. :of the organisms present at this period of the year are cloacæ and grunthal.
It will. be observed, by looking. at table X (a), that quite a fair proportion of the
remaining 25 per cent. of organisms have been derived from the Ootacamund reservoirs.
where, as we have seen, rain had fallen. It may be objected that in the method of
analyses which we adopted, the actual percentage prevalence of any particular organism
is not a satisfactory indication of their real frequency in water-supplies. This
objection does not apply when the average number of fœcalbacilliis between 1 and 1 0
p e r
c c . ;
b u t i t i s a r e a s o n a b l e c r i t i c i s m w h e n f e c a l b a c i l l i a r e s c a r c e , s u c h a s 1 .