LAND DRAINAGE PRACTICE. 4 1 



his conclusions leads to an error as far as drainage is 

 concerned. The greatest rise is found to be i foot in 

 i6-|- feet, and the least i foot in 55 feet. 



Since soils in which drains are placed may be like 

 any one of those upon which observations were made, 

 no soil would be found to which an average of widely 

 different results could apply except by accident or co- 

 incidence. It follows that the plane of saturation with 

 respect to the position of tile drains must be determined 

 for each kind of soil which is to be drained. Sugges- 

 tions upon this point will be made when we come to 

 consider the application of these physical soil charac- 

 teristics to the location of drains. 



Sources of Water Affecting the Soil, 



In locating drains it is necessary to consider the 

 source of the water to be removed. Primarily the rain- 

 fall is the source of all water-supply, but in land drain- 

 age work it is known by various terms describing its 

 local source. 



It is known as surface water when the direct rainfall 

 rests upon or flows over the surface of the land; local 

 soil zvater when a part of the surface water sinks di- 

 rectly into and saturates the soil and the subsoil ; flood 

 water, when water from some adjoining source flows 

 upon land, thereby throwing a greater quantity of water 

 upon it than the natural rainfall supply ; ooze or seep- 

 age water when it finds its way through the soil from 

 some higher elevation, and is arrested in its course by 

 a less slope or a change of subsoil structure (the 

 locality where the water appears is called -spouty"); 



