MARSHALL O. LEIGHTON 



Let us consider another case: 



SERIES "I." 

 PARTS PER MILLION. 



The analyses in the above table represent the city water of Des 

 Moines, Iowa. The first represents the water from the large well; 

 the second, from the small well; while the third is an average of 

 42 analyses of the supply, all made in the year 1897. Here again 

 comment upon the divergence of these figures with those given in 

 the standards of interpretation is unnecessary. Des Moines, Iowa, 

 is one of the most fortunate cities in the country from the stand- 

 point of typhoid rates. 



Series " J" contains respectively the average of analyses made from 

 the Oconee and the Shetucket wells of the Brooklyn water supply. 

 Throughout the entire period between 1897 and 1902 it will be 

 noted that in neither case does the average number of bacteria exceed 

 50 per c.c., and there were no positive tests for coli during the entire 

 period of investigation. Nevertheless, the nitrogen determinations, 

 according to the above standards of interpretation, would condemn 

 this water. 



SERIES "J." 

 PARTS PER MILLION. 



Another example is contained in Series "J." The samples were 

 taken from an isolated well at St. Cloud, Minn., and it must be con- 

 fessed that the analyses have an unfavorable appearance, especially 



