EUNNINa WATEE FOR FARM BUILDINGS 433 



with a short length of pipe with perforations which permit the 

 water to enter the pipe and keep out the gravel and sand. This 

 type is essentially for shallow wells, as with the cylinder in the 

 dry well water cannot be drawn up more than twenty feet by 

 suction. If a driven well is wanted and the water is more than 

 twenty feet below the surface, it is necessary to dig a deep dry 

 well so the cylinder can be installed below ground within suction 

 distance of the water. 



Drilled icells. — Fig. 215 (c) shows a drilled well, usually the 

 best type of all, for no impurities can enter from the surface. 



b 

 Fig. 215.- 



- Types of wells. 



This type of well consists of a small hole from three to fifteen 

 inches in diameter drilled through the various layers of surface 

 soil, clay and rock until a pure stream of water is reached. This 

 hole is lined with an iron casing w^hich prevents its caving in 

 and keeps out all the water except that which enters at the bot- 

 tom. The type of well can pass through as many water-bearing 

 soils as desired, and none but the water of the lowest streams 

 will enter. The casing is large enough to accommodate the pump 

 cylinder so that it can be lowered below the water surface or as 

 near the water as is necessary, and water can be pumped from 

 any required depth. 



Fig. 215(d) shows a drilled well with a dry well installed above 

 it to accommodate the lower half of a pump made for under- 

 ground discharge. 



