FUTILITY OF A SANITARY WATER ANALYSIS 53 



in gravel. In this case the chemical examination revealed the pres- 

 ence of an excess of chlorides and nitrates while bacteriological 

 investigation showed nothing which would cause suspicion. This 

 instance is cited by Professor Mason as one in which "the danger 

 signal was held out by the chemical side of the investigation alone." 

 The writer is of the opinion that the "danger signal" was not the 

 findings of the analysis, but the occurrence of disease in that residence. 

 It should have caused an immediate examination of the premises, 

 and such examination would have revealed the fact that the sewage 

 was discharged into a dry-steyned cesspool, that the well was only 

 jour yards away and that both were sunk in gravel. In the face of all 

 our knowledge of the transmission of water-borne diseases, and in 

 view of our decades of experience with infected wells, from historic 

 Broad Street down to the present, why should any competent obser- 

 ver, with the above related facts before him, find it necessary to 

 fuss with an ammonia stifl or, for that matter, with a Petri dish? 

 Taking a broad view of the subject of well supplies, we may safely 

 exclude all wells in questionable places; and the careful observer 

 can usually define such places. 



All of the above discussion with reference to the needlessness 

 of sanitary analyses, when other and more expeditious methods 

 can be used, is based upon the temporary admission that such anal- 

 yses afford data whereby dangerous animal pollution can be dis- 

 tinguished from harmless vegetable matter. If we return now to 

 the original contention that standards of purity, bases of interpreta- 

 tion, composition ratios, or by whatever name they may be called, 

 are met with equal faith by the normal water and by the dilute sewage, 

 and sum up the two lines of evidence, we have what the writer feels 

 justified in regarding as an established case against the sanitary 

 analysis as an index of dangerous water pollution. 



