210 COMPETITION OF LOCAL SOURCES OF SUPPLY 



Ground water supplies are drawn from the underlying soil 

 and are to be had only where that soil is porous. If the soil is 

 clay, or if granite or other impervious rock comes near the sur- 

 face, there is not much ground water to be had. But, if there 

 are deep beds of sand, gravel, or sandstone, or other pervious 

 material, ground water supplies are found. The interstices of 

 the material serve as a natural reservoir to hold the water that 

 reaches them from the rainfall, and to make it available at all 

 seasons to those who provide themselves with the wells and 

 pumps that are necessary to utilize it. 



Many large cities are built over underground reservoirs in 

 such water bearing materials, and the quantities of water that 

 may be drawn from them under favorable conditions are very 

 large. 



Ground waters drawn from fine-grained materials are usually 

 of better sanitary quality than surface waters. Where the popu- 

 lation is not too dense in suburban and outlying districts the 

 quality of the water obtained from wells is often excellent. As 

 the population in the neighborhood of the wells increases the 

 water becomes less desirable in quality, although there are 

 occasional exceptional conditions under which good water is 

 obtained even in the centers of cities. After the water is no 

 longer suitable in quality for domestic use it may continue to 

 be used for other purposes. 



Underground waters are usually harder than surface waters 

 and less desirable for boilers, washing and many industrial uses; 

 their field of usefulness is thus restricted; but, where they are 

 much cheaper, there are many uses which may be served by them. 



A public water supply may feel the competition of well 

 waters at tunes with nearly all classes of consumers. For the 

 small houses, people who have good wells and who have been, 

 and are, dependent upon them are slow to take water from the 

 public supply. This has been the experience in many American 

 cities, and especially in the smaller towns, and it is always 

 surprising to find how many people there are who will not 

 willingly take water from the public works where the old wells 

 are reasonably satisfactory. 



