January 12, 1906.] 



SCIENCE. 



65 



by filtration through soil having direct 

 connection with the water in the well, owing 

 to the seamy or faulty character of the 

 rock or to the percolating water wearing 

 channels through the rock, as often occurs 

 in limestone formations. The source of 

 pollution may, therefore, be many miles 

 from the well, and through careful study 

 of the geological formation, the dip of 

 strata and general characteristics of the 

 neighborhood should be made, the main 

 reliance for deciding whether or not the 

 water is a polluted one must often be the 

 data obtained from the chemical and bac- 

 terial analyses. 



Unfortunately, however, in the study of 

 artesian water perplexing chemical and 

 bacteriological results are often obtained. 

 In artesian waters so situated that surface 

 pollution seems impossible, amounts of 

 nitrogen as free ammonia, as nitrites and 

 as nitrates have often been found which, if 

 occurring in ground waters, would cause 

 them to be considered as polluted. The 

 nitrogen of the nitrates in these waters may 

 be due to fossil remains, and the nitrogen 

 as nitrites and as free ammonia to the 

 reduction of the nitrates by chemical ac- 

 tion, as contact with iron sulphide, and the 

 occurrence of the nitrogen as free ammonia 

 also sometimes to some salt of ammonia 

 existing in the strata through which the 

 ground water passes. On this account the 

 determination of the nitrogen content does 

 not give as satisfactory data from which 

 to draw conclusions as those obtained from 

 the analysis of ground water. 



The interpretations of the data obtained, 

 however, always bearing the above facts in 

 mind, are nearly the same as those stated 

 when considering ground waters. An un- 

 polluted artesian water should not contain 

 any nitrogenous or carbonaceous, organic 

 matter and consequently the nitrogen as 

 ' albuiiiinoid ainmonia should not be over 

 0.02 milligram per liter and the oxygen 



consumed, nitrites and mineral reducing 

 substances being absent, should not exceed 

 one tenth of a milligram. 



The chlorine factor is of much less im- 

 portance in the study of artesian waters 

 than in the other two classes, for, as a rule, 

 we have little or no knowledge of the nor- 

 mal chlorine of deep waters of any given 

 region and consequently this datum has 

 only the same value that it has in the 

 analysis of surface waters in localities 

 where the normal chlorine has not been 

 determined. 



Baeterially an artesian water should be 

 a very pure water and at one time it was 

 considered that an unpolluted artesian 

 water was a sterile water. To-day, how- 

 ever, this is not the case. Examination 

 of wells has shown that while in a few 

 cases the water may be sterile, in the 

 majority bacteria are present in varying 

 numbers. These are, however, generally 

 of slow-growing types and are not indi- 

 cative of pollution. Should an artesian 

 water, not in a region of thermal springs, 

 show bacteria which develop in consid- 

 erable numbers at the body temperature, 

 the interpretation would be the same as 

 in a ground water, that unpurified water 

 or sewage was entering the well either from 

 the immediate environment or through fis- 

 sures and crevices in the lower strata. 

 Acid-forming bacteria and the colon bacil- 

 lus should never be found in artesian 

 waters. 



I am afraid I have already occupied by 

 far too much of your time in giving my 

 opinion as to the sanitary value of a water 

 analysis and the information that can be 

 derived from such an analysis, and in con- 

 clusion would only reiterate that to form 

 a judgment as to the wholesomeness of a 

 water the data of a sanitary water analysis, 

 the source of the water, whether surface, 

 ground or artesian, must be known; that 

 a survey, even of a surface water, though 



