250 Timehri. 
Faint traces of Nitrites and Nitrates were found in seven specimens. 
The hardness varied between 1.2 and 5.5 parts per 100,000. The solids 
were between the following figures: Organic 7.0 to 39.0; Inorganie 2.4 
to 24.0 in parts per 100,000. 
In placing hygienic values on these analyses we were confronted by 
the difficulty that the usual standards relied upon in Europe for detection 
of sewage were of little avail especially from a chemical standpoint. For 
example, the albuminoid and free or saline ammonia figures are so high in 
the peaty, and even the rain waters of this colony that a small extra 
amount present as due to sewage contamination cannot possibly be identi- 
fied:as such. Further Nitrites and Nitrates, usually accepted as indicators 
of pollution at a somewhat remote date, were almost invariably absent. 
Not because there was no sewage present (that was abundantly proved by 
the topographical and bacteriological data), but because the waters of the 
colony contain a large amount of reducing substances, ferrous iron 
amongst others, which prevent the normal oxidation of Ammonia to 
Nitrates taking place. Under these circumstances, after consultation 
with Professor Harrison, we decided to fall back upon the figures given 
for Chlorides and Phosphates as of most value. 
Chlorides are looked upon by sanitarians as evidence of urine 
contamination, in the absence of sea water. Phosphates are the most 
stable of the ultimate products of decomposition of faecal material and 
come from no other source save chemical manures, ete. If the chlorine 
figure is high, that is, in excess of the average for the district, it may 
reasonably be inferred that the material which yields the chlorine is a 
great part of animal origin. For the purpose of comparison we, there- 
fore, in agreement with Professor Harrison, propose to adopt a standard 
of .8 parts per 100,000 of Chlorine, and to regard with suspicion water 
containing more than .05 parts of Phosphates per 100,000. These 
tigures were of course adopted after comparison between the original 
water as obtained from the source in the savannah lands, and the water 
after admission to the drinking water trenches. For example, if the 
Phosphates amount to nil or at most to a mere trace in the original 
savannah water, the fact that it increased greatly later, will be proof 
positive either that the water has been exposed to animal pollution, or 
that surface water from manured lands has gained access. In either case 
this is sufficient evidence to condemn it for drinking purposes. Of a 
large number of samples examined the table above indicates that only 
four showed a reasonable degree of freedom from pollution as judged 
by the chlorine figure, whilst as regards the Phosphate figure not one 
sample fell within the limits given by Hehner as constituting a water 
“free from suspicion.” 
From a bacteriological point of view the chemical results were fully 
confirmed. A water which is contaminated with sewage sufficiently to 
yield evidence of pollution by chemical methods will show overwhelming 
evidence pointing to the same conclusion on bacteriological grounds, 
NT ag OBS 
