STUDY OF WATER. 423 



iu 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," 

 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 M'ater 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 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 ^vater 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 organisnis 

 may have been detected, still, waters in which such 



