218 KIOHMONI) AND OANA. 



In interpreting the results of the chemical examination of tliese watei'S, 

 the following conclusions would ordinarily be drawn : Waters from wells 

 Xos. 1, 2, 3, 4, 5, 6, 7, and 9 would he considered entirely unsuited for 

 drinking purposes in every respect on account of the high chlorine figures 

 together witli an excess of nitrogen in all of its forms. While the absence 

 of chlorine is sufficient proof of the absence of sewage contamination, its 

 presence does not necessai'ily indicate sewage contamination in countries 

 adjacent to the sea. Therefore, not mucli importance should be placed 

 upon high chlorine figures alone, but when they are accompanied by 

 excessive amounts of nitrogen, particularly in tlie form of albuminoid 

 ammonia and nitrites, the indication of pollution with sewage or drainage 

 from refuse animal matter is almost conclusive. 



Waters N'os. 8 and 13 would be considered of a doubtful charactei' as 

 the nitiogen as nitrites is above the allowable limits and the nitrogen in 

 its other forms is too near the border line for safety. 



Waters Xos. 10, 11 and lr3 are well within the allowable limits of safety 

 as regards the nitrogen in all its forms, the oxygen consuming power and 

 chlorine content. In fact these waters from a chemical standpoint appear 

 better in every respect than do many deep well waters which from the very 

 nature of their source are free from surface pollution. When judged 

 from the chemical findings alone, these three Avaters would be considered 

 entirely safe for drinking purposes; hence too much reliance should not 

 be placed on the sanitary chemical analysis of drinking waters alone. It 

 is only when the source of the waters — i. e., location and kind of well — 

 the physical characters and results of a biological examination of the water 

 are known that the results of a sanitary chemical examination are of 

 assistance in judging whether the water in question is potable. 



