BAGTERIOLOGICAL STUDY OF WATER. 489 



unquestionably a suspicious indication, but in a district 

 close to the sea or near salt deposits, for- instance, where 

 the water generally is high in chlorine, the value of the 

 indications thus afforded is very much diminished 

 unless the amount found in the sample under examina- 

 tion greatly exceeds the normal " mean," previously 

 determined, for the amount of chlorine in the waters of 

 the neighborhood. 



A striking example of such a condition as the latter 

 recently occurred in the experience of the writer while 

 inspecting a group of water-supplies on the east coast 

 of Florida. In each instance the water was obtained 

 from properly protected artesian wells, ranging from 

 200 to 400 feet deep, and located within a few hundred 

 yards of the sea. The first sample that was subjected 

 to chemical analysis revealed such an unusually high 

 proportion of chlorine that, had this sample alone been 

 considered, the opinion that it was polluted by human 

 excreta might have been advanced. To prevent such 

 an error samples of water from a number of wells in 

 the neighborhood were examined, and they were all 

 found to contain from ten to twelve times the amount 

 of chlorine that ordinarily appears in inland waters, the 

 excess being evidently due to leakage through the soil 

 into the wells of water from the sea. In short, the pres- 

 ence of an excess of chlorine in water, while often indi- 

 cating pollution from human evacuations, may, never- 

 theless, sometimes arise from other sources; but the 

 presence in water of bacteria normally found in the 

 intestinal canal can manifestly admit of but one inter- 

 pretation, viz., that fecal matters have at some time 

 and place been deposited in this water, and that while 

 no specific disease-producing organisms may have been 



