162 POULTRY CULTURE 



amount of water coming from such a spring depends on the 

 rainfall and upon the collecting area. 



An inch of rain delivers a Uttle over A)4, gallons on the 

 square yard surface, which is 101 tons on each square acre. 



In falling during rainfall the water absorbs the impurities of 

 the air which, in certain manufacturing communities, may be 

 nitrous or nitric acid, ammonia salts, sulphurous acid, and 

 products of combustion of coal and other combustive prod- 

 ucts used in generating power. 



The first rain that falls contains more of these products or 

 impurities as well as bacteria. 



Water collected in large lakes or reservoirs or ponds is 

 attacked with vegetable growth on account of the organic 

 matter contained in the water, which organic matter has been 

 gathered from the watershed during the rain and drainage. 



The vegetable growth appears as a green scum. Most 

 vegetable matter of this kind is not poisonous, though in 

 India a poisonous kind has been found. 



Vegetable growth has a tendency to purify the water, as it 

 utilizes the organic matter the water contains. 



River water usually contains more impurities than pond 

 water. It is common practice for cities and private individ- 

 uals to empty sewage and to dispose of other waste matter by 

 aid of the rivers. 



Often rivers are polluted with germs of disease and form one 

 means of spread of contagious diseases. 



Wells are classified as shallow, deep, and artesian. These 

 form a source of pure water-supply, provided they have not 

 become polluted through soil seepage. 



One of the sources of pollution of shallow wells and springs 

 is cesspools and barnyards, as well as outdoor privies. 



The impurities found in water are of two kinds — namely, 

 inorganic and organic. The inorganic impurities are the salts 

 of met.als. Inorganic material may gain entrance into the 

 water by passing through pipes, canals, from river beds, from 

 watersheds, from irrigation ditches, and by percolation 

 through soil and over rock. 



The inorganic impurities depend upon the geologic forma- 

 tion. 



