CHAPTER “At. 
THE APPLICATION OF THE’ FOREGOING RESEARCH TO WATER 
ANALYSIS. 
Ir will, I think, be admitted that a thorough knowledge 
of the subject of the self-purification of water is likely to be of 
great value to the water analyst, particularly as we have 
already shown, there are certain well defined stages in the 
process. There are, however, several points which should not 
be overlooked in dealing with water analysis as a whole. 
In the first place, it is pretty well recognised that to send a 
sample of water to an analyst without giving him any clue 
as to where the water is taken from, and to omit all details 
regarding the obvious chances of pollution, the amount 
of rainfall, etc., is a futile thing to do. Those who are 
inclined to scoff at water analysts frequently tell us that 
an inspection of a supply is of much more value than 
an analysis. In some respect this is undoubtedly correct. 
Anybody who has been in the habit of making sanitary 
inspections can with a very reasonable amount of certainty 
give an opinion as to the /zkelthood of dangerous pollution being 
present in any particular source of supply. The following is— 
an instructive example. Two samples of water were sent for 
opinion as to which of the two sources was likely to be the 
better supply for some troops engaged in manceuvres. 
Sample No. 1 came froma stream running down a mountain 
side and was reported to contain a very large number of fecal 
organism. Sample No. 2 came from a well situated near a 
village. The analyst remarked that the latter water was a 
pretty good one, and contained about 1 fecal organism in 4 or 
5 c.c., consequently he recommended the well to be used as a 
source of supply to the troops. The Medical Officer with the 
troops, who received this information, ignored it, because the 
well was situated in a village where cholera was not infre- 
quently present, whilst the stream came from the side of a hill 
on which a fair number of cattle grazed during the day, but 
