58 



AGRICULTURAL ENGINEERING 



of a layer of soil if a suitable outlet be provided. When 

 water exists on soil particles in a very finely divided state it 

 is often called hygroscopic water. It is understood that 

 capillary water, as defined, would include this hygroscopic 

 water or moisture. 



Lands Requiring Drainage. In general, land having an 



Fig. 4 2. A good crop of corn on land which was a swamp the year before. 



excess of water over that required to furnish the best con- 

 ditions for plant growth, needs under drainage. The exact 

 conditions prevailing when an excess is present may be out- 

 lined as follows: 



1. Comparatively flat land in which water collects in 

 basins or ponds from the higher surrounding land. 



