31
hour and was very heavy while it lasted.. The consequence would. be that a very
considerable volume of this water would run off the land into streams. Had the
rainfall been spread over a longer period than half an hour or so, the water would
probably have found its way into the subsoil waters. Fœcal bacilli are to be found
in .1 of a cc. which is somewhat better than the previous week. Nearly all the
organisms isolated were coli communis. These two analyses (samples 2 and 3) are
particularly interesting, for they demonstrate clearly the fact, that has long been
known to sanitarians in the east, viz., that the first rainfall after a prolonged drought,
especially if the rainfall is not excessive, always causes a serious contamination of
surface waters. It is not infrequent to find that the early rains are accompanied by
outbreaks of cholera, which disappear after a considerable downpour. In the case of
the King Institute well, we consider that there is very little doubt that these organisms
were washed into the well from bacilli living in the soil. The reasons for supposing
that these organisms must come from some strata in the soil, probably somewhere near
the level at which the subsoil water remains permanently, are (1 ) it is most improbable
.
that coli communis would remain alive for months of dry hot weather on the surface
and (2) if these coli came from the surface other fecal organisms would certainly be
mixed. with them. The exact layer in the ground where these organisms lived, and
the reason why coli communis so largely predominates is not by any means apparent ;
we shall show later that in the upper layer of the soil coli communis does not survive
long.
Sample No. 4.—There having been no rain during the previous week, the well
water has gone back to what may be termed its hot weather condition. Fcal bacilli.
are still present in 1 cc. but they are almost entirely B. cloace. It will be noticed
that the recent rainfall was not sufficient to cause any marked raising of the level of
the subsoil water.
Sample No. 5.—This sample shows a considerable increase in the purity of the
water. The reason for this is not known, but it may be connected with recent showers.
The rainfall during the week was . 05 of an. inch, and as usual, when rain has occurred
coli communis is present among the bacilli isolated, the remaining ones being cloacæ.
Sample No. 6.—Just previous to this sample being taken, i.e., on the evening
of the 7th August 2 . 22 inches of rain fell. Unfortunately, however, the influence
of this rainfall had not made itself felt in the well by early on the morning of the
8th, when the samples were taken. The consequence is that this sample presents
no difference from the others, the predominating bacilli being cloaca, with one B.
grunthal.
Sample No. 7.—The rainfall during the week was 31 of an inch,. but the
2 inches, referred to above, should not be overlooked. Fœcal bacilli are present in
1 cc., but this is the first instance where the presence of undoubted surface pollution
is observed. In the bacilli isolated we have no less than five different organisms. This,
we consider, is due to the fact that long standing surface pollution has been washed
into the subsoil water. Probably if a sample had been taken shortly after the heavy
downpour on the 7th coli communis would also have been found. The organisms
present are the ones commonly met with in cow-dung and human fœces
Sample No. 8.—Rainfall during the week consisted largely of one very heavy
downfall of 3 . 6 inches, in the early morning of the 25th August. Here again we have
clearly demonstrated the result of surface pollution being washed into th.e subsoil, and
thence to the well. Among the 20 colonies examined there are some six different
varieties present. Coli communis are common, and fecal bacilli are present in .1 cc.
The level of the subsoil water has risen about 2 feet. There i.s now 18 feet of water
in the well.
Sample No. 9—Shows a very similar condition of affairs, but in this sample the
faecal bacilli are only found in 1 cc., coli communis and B. grunthal preponderate in
the bacilli isolated.
The number of coli present in combination with others is not a good sign ; it
strongly suggests that the ground in the neighbourhood has been fouled recently.
possibly by the engine attendants or cattle.