i8o Elements of Water Bacteriology. 



found that the bacteriological examination offers a more 



delicate and a more certain index of the quality than 



may be obtained by chemical analysis. In a number of 



instances, springs located in pastures have become slightly 



polluted by animals, but to so small an extent that the 



chemical examination gave no indication of trouble. 



The bacteria, however, increased greatly in number, and 



colon bacilli coidd be readily isolated from 75 per 



cent of the i-cc. samples of a long series used in 



making the presumptive test. A single case may sufl&ce 



as an illustration. This was a spring located on a hill in 



Hopkinton, Mass. 



The chemical analysis was as follows: 



Color None 



Turbidity None 



Sediment None 



Odor (hot) None 



Odor (cold) None 



Parts per Million. 



Total solids . . 33.0000 



Loss on ignition 7.0000 



Fixed residue 26.0000 



Hardness 11.0000 



Chlorine 10.0000 



Nitrogen as — 



albuminoid ammonia 0.0000 



free 0.0000 



nitrites 0.0000 



nitrates u.oooo 



The bacteriological examination showed a total count 

 of. 375 bacteria per c.c. and a 37-degree count of 350 

 per c.c. 



