84 DOMESTIC WATER SUPPLIES FOR THE FARM 



If a well is to be located at a less distance from source of 

 pollution than that prescribed, it should be dug on higher ground, 

 so that the moving ground waters will carry the impurities away 

 from, rather than toward it. It is far better to spend the few ad- 

 ditional dollars required (because of the greater depth to the 

 water) to sink a well on higher ground than to risk sickness by 

 locating it where there is danger of pollution. It is not sufficient 

 that the mouth of the well be above the source of pollution. The 

 water level in the well must also be above the source of contami- 

 nation, even when farthest depressed by drought or pumping, for 

 otherwise pollution-bearing seepage might soon find its way to 

 the well. 



Digging the Well. -- The process of constructing the common 

 dug well is so simple and so familiar that a few brief statements 

 will suffice. 



By far the greater number of dug wells will naturally be of 

 circular cross section, since, for a given capacity of water, less 

 material will be required for curbing. Moreover, the curbing, if 

 of stone or brick, is more easily laid and is less liable to cave under 

 the pressure of the surrounding earth. 



The original excavations commonly vary from 6 to 10 feet in 

 diameter where stone is to be used for curbing. Such curbings, 

 even in the smaller and shallower wells, are seldom under 15 

 inches in thickness and in the larger and deeper wells often have 

 a thickness of from 2 to 2^ feet. The finished wells, where the ex- 

 cavation is 6 to 10 feet, will, therefore, seldom be more than from 

 3 to 6 feet in diameter. When bricks are used for lining the well 

 the thickness of the walls is usually much less, being seldom more 

 than half that of the stone curbs. The same is true of the cement 

 curbs, which are occasionally used for that portion of the well 

 lying above the water level. A thickness of 12 to 15 inches is 

 usually sufficient for depths down to 15 or 20 feet, but some- 

 what greater thicknesses are required for the deeper wells. The 

 cement is laid between inner and outer forms, or, where the earth 

 is stiff enough to stand alone, between an inner form and the 

 outer wall of the excavation. 



