APPENDIX B. 
A FEW REMARKS ON CHEMICAL ANALYSIS OF TROPICAL 
WATERS. 
ALTHOUGH this work is largely taken up with the bac- 
teriology of surface waters in India, for the benefit of those 
who are engaged in analysing the waters a few points may be 
briefly referred to, concerning the chemical analysis. From 
a large number of analyses of surface waters, it may be stated 
that some slight differences would be noticed between the 
waters in the East and in the West. By far the most impor- 
tant of these points is the great rarity of nitrates in rivers 
and lakes. From some hundreds of samples we have proved 
that nitrates are either entirely absent or only present in 
very small quantities in lakesand most rivers. So universal is 
this the case, from one end of India to the other, that there must 
be some very widespread condition to account for it. It is 
well-known to all in charge of sewage works that, asa general 
rule a shower of rain, afteraconsiderable interval of drought, 
causes nitrates to be found in the sewage, due in all proba- 
bility to the action of nitrifying organism on the surface of 
the soil. It is perfectly obvious that this condition does not 
occur in the East, and probably the explanation is that the 
sun’s rays kill off these particular bacilli that are present on 
the surface. Boulanger, Massol, Calmette and others have 
shown that most nitrifying organisms are easily killed at 
comparatively low temperatures. The temperature of the 
ground in an ordinary Indian summer is very high, and in all 
probability causes the death of these bacilli. Ground waters 
obtained from wells and springs, etc., are, however, quite as 
rich in nitrates in the East as in the West. Indeed there 
are in India several districts where nitrates are so plentiful 
in the soil that a certain caste of people separate it and sell it. 
Surface waters as a rule contain a very high albuminoid 
ammonia figure, much of which is due to vegetable matter. 
In all probability the absence of the nitrifying power on the 
