THE FARM WATER SUPPLY 



75 



More important than the amount of matter dissolved in the 

 water, is the composition of that matter, a study of which is 

 necessary in order to judge the source of the substances in so- 

 lution and whether a water is dangerous or not. The best evi- 

 dence of the origin of the matter dissolved in water, is obtained 

 by determining the amount of chlorine present. This element 

 is one of the two that form common salt and is almost inva- 

 riably present in a natural ground water ; but in only slight 

 traces, except near the sea-coast where the spray from the 

 ocean is taken up bodily by the wind and borne inland. The 

 proximity of cultivated fields must modify the amount of 

 chlorine naturally present in a spring-water, owing to the ap- 

 plication of fertilizers. 



The lowest results obtained in waters from apparently un- 

 polluted springs are given in the table. It will be noticed that 

 the figures decrease rapidly as the distances of the localities 

 from the coast increase. These figures are similar to those ob- 

 tained in iSIassachusetts from normal waters.^ 



CHLORINE IN UNPOLLUTED GROUND WATERS. PARTS IN 100,000. 



To judge the healthfulness of a water after knowing some- 

 thing about the origin of its soluble constituents, the most stress 

 is laid upon the relative quantities of four different compounds 

 of nitrogen, an element occurring in all animal and vegetable 

 tissues, as well as forming four-fifths of the atmosphere. It 

 occurs in water in the form of ammonia, soluble organic mat- 

 ter and two classes of compounds, called respectivelv nitrites 

 and nitrates. 



The ammonia in unpolluted spring-water is due mainly to 



iRept. Mass. State Board of Health, 1890. 



