l899-'oo TRANSACTIONS 145 



4) from soakage, and consequently, most of them are contamin- 

 ated with sewage which has undergone no such amelioration by 

 soil-filtration as would have resulted from proper construction. 

 Not one of them is certainly a safe well ; while No. 7 cannot but 

 be a most dangerous supply. 



In the following table I have placed the resulting numbers 

 from examination of 21 wells — varying from 10 to 20 feet in 

 depth : These samples were taken on the same day, and from 

 the same region : 



It is quite likely that most of these wells derive the main 

 portion of their supply from the ground water of the locality ! 

 but it is very certain that most of them are contaminated with 

 soakage water. The first four are among the deepest of these 

 wells, and as likely to be true ground water wells as any ; yet 

 their chlorine content is not high — in fact, the very highest 

 chlorine numbers in this list correspond to decidedly shallow 

 wells, whose contamination by sewage is beyond a doubt. 



The following six wells, are decidedly deep wells, and should 

 give pure water, were they properly protected from soakage. 



