CHAPTER X 



THE SIGNIFICANCE AND APPLICABILITY OF THE 

 BACTERIOLOGICAL EXAMINATION 



Sanitary Inspection and Sanitary Analysis. The first 

 attempt of the expert called in to pronounce upon the 

 character of a potable water should be to make a 

 thorough sanitary inspection of the pond, stream, well 

 or spring from which it is derived. Study of the pos- 

 sible sources of pollution on a watershed, of the direc- 

 tion and velocity of currents above and below ground, 

 of the character of soil and the liability to contamina- 

 tion by surface-wash are of supreme importance in 

 interpreting the analyses to be made. In many cases, 

 however, the results of the sanitary inspection will 

 be found to be by no means conclusive. If house or 

 barnyard drainage or sewage is actually seen to enter 

 a water used for drinking purposes it is obviously 

 unnecessary to carry out delicate chemical or bacteri- 

 ological tests to detect pollution. On the other hand, 

 no reconnoissance can show certainly whether unpurified 

 drainage from a cesspool does or does not reach a 

 given well; whether sewage discharged into a lake 

 does or does not find its way to a neighboring intake; 

 whether pollution of a stream has or has not been 

 removed by a jcertain period of flow. Evidence upon 



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