CISTERNS AND HOUSE TANKS 



149 



is likely to carry more bacteria and other forms of contamination 

 than the unfiltered water. 



Inasmuch as it is rare that the farmer possesses the time, to 

 say nothing of the requisite knowledge and skill, to properly care 

 for such mechanical filters, their use is of doubtful advisability, 

 especially as the desired purification can be accomplished with 

 greater facility and almost equal effectiveness by the use of auto- 

 matic deflectors or similar devices. 



Combination Wells and Cisterns. Although cisterns of the 

 dimensions indicated in the preceding section will supply enough 

 water for domestic use in a small family, they will not supply 

 enough for stock. In fact, unless the farm buildings are very 

 large or numerous it is, as a rule, impracticable to procure enough 

 cistern water to supply more than a few head of stock, and it is 

 therefore generally necessary to utilize the ground-water supplies. 

 These are sometimes too far from the surface to be available 

 during the summer, but there is almost always enough water in 

 the ground in winter, and the ideal provision would be to store a 

 portion of the winter supply for summer use. 



In the winter the ground-water level is high, often standing 

 only a few feet below the surface, but in summer it is usually 

 much lower, often many feet from 

 the top of the ground. If a well is 

 carried deep enough sufficient water 

 can in most places be obtained, but 

 many wells are too shallow to give 

 never-failing supplies, and as a con- 

 sequence they may be short of water 

 in times of drought. If the water 

 in the well in the winter could be 

 retained till summer, there would be 

 little difficulty with the supply of 

 most wells, but, unfortunately, as the ground-water level falls 

 the water in the wells falls also. In Fig. 65 ac indicates the 

 depth of water in a well during the winter, and be indicates its 



FIG. 65. Combination well and 

 cistern. 



