324 L. A. ROGERS 



Ten cultures were obtained from two samples collected near Wash- 

 ington when the river was in normal flow. These included three cul- 

 tures of the B. coli type which were typical in every way except that 

 they had a hydrogen ion limit of 5.2 to 5.4. In this regard they corre- 

 sponded to the cultures held in water many weeks rather than with 

 freshly isolated fecal cultures. 



The 7 B. aerogenes cultures included 5 which fermented adonite 

 and starch and otherwise agreed with the fecal type. 



No. SO. Anacostia River. One sample was taken at the bridge below 

 Bladensburg when the flow was above normal. This stream is pol- 

 luted by the sewage of Hyattsville and other smaller villages. All of 

 the nine cultures were of the B. coli type and had a hydrogen ion limit 

 of 4.8 to 5.3. 



These results indicate a high pollution of recent origin, comparing 

 as they do with results obtained a short distance below the sewer in 

 Rock Creek and Wolf Creek. 



No. 28. Pimmit Run. This is a relatively small stream flowing into 

 the Potomac at Chain Bridge. It probably receives no direct sewage 

 but flows through an agricultural country from which it is contami- 

 nated by surface wash. No B. coli cultures were obtained from the 

 one sample examined but of the 8 B. aerogenes cultures isolated 6 

 fermented adonite and starch and were probably of fecal origin. One 

 fermented starch but not adonite and one fermented neither adonite 

 nor starch. 



No. 26. Spring near Chain Bridge. This spring is in a rather sparsely 

 settled suburban district and was carefully protected from surface 

 contamination by tiles and stone work. The source of the water was 

 not evident and the possibility of contamination was a matter of 

 conjecture. 



The houses in the vicinity were, for the mo!?t part connected with 

 sewers. Five B. aerogenes cultures were isolated, all of which fer- 

 mented adonite and starch and were therefore of the fecal type. 



No. 11. Spring near Little Falls. This spring at a camp on the 

 Virginia shore of the Potomac was carefully protected by stone work. 

 The shore is wooded for nearly a half mile from the river. The camps 

 in the vicinity are occupied at irregular intervals and there are no 

 houses within a mile. 



The spring flows from gravel at the foot of an abrupt rocky hill and 

 so far as an examination of the surroundings shows there is no reason 

 to expect contamination. Of the 5 cultures isolated 3 were B. coli 

 and two were B. aerogenes fermenting adonite and starch. 



