444 BACTERIOLOGY. 



tionably 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 examination 

 greatly exceeds the normal " mean/ 7 previously deter- 

 mined, 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 chem- 

 ical 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 ordi- 

 narily appears in inland waters, the excess being evi- 

 dently due to leakage through the soil into the wells of 

 water from the sea. In short, the presence of an excess of 

 chlorine in water, while often indicating pollution from 

 human evacuations, may, nevertheless, sometimes arise 

 from other sources, but the presence in water of bacteria 

 normally found in the intestinal canal can manifestly 

 admit of but one interpretation, viz., that fecal matters 

 have at some time and place been deposited in this 

 water, and that while no specific disease-producing or- 

 ganisms may have been detected, still, waters in which 



