BACTERIA DEVELOPING AT DIFFERENT TEMPERATURES 237 



intermittent sewage niters, and practically absent from the fourth, 

 while they were present in greater or less numbers in the sewages 

 and in the effluents from the contact and trickling niters through 

 which the sewage passed more rapidly. The presence of such small 

 numbers of this type of bacteria in the polluted river water, and 

 of similar numbers in the effluents from the primary water filters, 

 cannot be accounted for at the present time. 



TABLE No. 4. 



AVERAGE NUMBER OF BACTERIA AND Aero - PRODUCERS DEVELOPING AT 20, 40, AND 50 C. WITH 

 DIFFERENT CLASSES OF WATERS. 



Bacterial ratios, 50 series. The bacterial ratios for the different 

 waters included in the 50 series are shown in Table 5. In general 

 the 2O-4O bacteria ratios and the ratios between the 20 bacteria 

 and the 40 acid-producers were much greater for the sewage and 

 the effluents from sewage filters than for the other waters, although 

 there are a few exceptions to this rule. The 20-40 ratios for the 

 polluted river water in each case were much less than the correspond- 

 ing ratios for Applied 216 and for the effluents from Water Filters 

 No. 8, 216, and the City Filter, indicating that the removal of the 



