WATER 



(1. Spring-water. \ 

 Wholesome. J2. Deep well-water. I ^^ry palatable. 



is. Upland surface-water. "i Moderately 



j'4. Stored rain-water. i palatable. 



Suspicious. J5. Surface-water from culti-1 



' vated land. 



(6. Eiver - water to which [ Palatable. 

 Dangerous, j sewage gains access. 



\7. Shallow well-water. 



Hygienically the classification would be as follows : 

 1. Pure and wholesome water ; 2. Usable ; 3. Suspicious ; 

 4. Impure. The characteristics of a pure water are absence 

 of colour, taste, smell, or extreme hardness ; the more a 

 water deviates from this, so will it pass into the other 

 classes named. 



IMPURITIES FOUND IN WATER. 



The impurities found in water are of various kinds, but 

 may be generally stated to be organic and inorganic. The 

 organic impurities are animal and vegetable substances in 

 all forms, from disease-producing matter to harmless vege- 

 table growths. The inorganic impurities are the salts of the 

 metals. These impurities obtain entrance into the water 

 in various ways, either at its source or during its passage 

 through rivers, canals, or pipes, or even after its delivery 

 to the place of consumption. The impurities obtained at 

 its origin will depend upon the geological formation of the 

 soil in which the source is situated. If the ground is charged 

 with the products of animal excreta and refuse, the water 

 derived from it will contain these products in solution ; but 

 it is evident that some soils or formations are more impure 

 than others, and this difference in the degree of soil impurity 

 depends upon the power the ground possesses of oxidizing 

 or destroying the tilth which is carried into it. Where 

 rapid destruction of this occurs, we may expect to find a 

 purer water than in formations where it does not occur. 

 Moreover, the porosity of the soil, especially when of great 



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