248 



Stephen DeM. Gage 



between the pond and well waters and the other classes of samples 

 is indicated by the large number of samples which do not contain 

 acid-producing bacteria at 40° C. A distinction occurs between 

 the pond and well waters, as shown by the fact that the ratios for 

 the former are distributed among the higher values, while the ratios 

 for the latter are distributed among the lower values. The normal 

 ratio is not apparent for the pond waters, but the normal ratio for 

 such samples of well water as contained bacteria of this type falls 

 between the limits previously noted for other classes of samples; 

 that is, between i and 5. The distribution of the bacteria-5. coli 

 ratios for all samples from these 13 different sources is shown in 

 Table 14: 



TABLE 14. 



Distribution of Bactekia-B. coli Ratios Among Different Samples for Various Classes of 



Waters. 



Above 15 



Lawrence sewage 



Septic sewage 



Strained sewage 



Sand filter effluents.. . . 

 Contact " " .. . . 

 Trickling filter efi3uents 



Merrimack River 



Applied 216 



Filter No. 216 



Other water filters 



Sea waters 



Pond waters 



Wells 



3 

 o 

 o 



12 



12 



8 



o 

 o 

 o 

 9 

 5 

 7 

 o 



In Table 15 is shown the distribution of the ratios between the 

 bacteria and the acid-producers developing at 20°, 30°, and 40° C. 

 In computing the values in this table only samples are included 

 which contained bacteria capable of development at the given tem- 

 perature. The difference between these ratios and the ones pre- 

 viously discussed consist in their much wider distribution, and this 

 has made necessary the grouping of the ratios between somewhat wider 

 limits. 



The normal ratios between the bacteria and acid-producers at 20° 

 for Merrimack River water and Applied 216 appear to be about 

 20 in each case. The normal ratio for the effluent from Filter No. 



