SOIL WATER 81 



Open ditches require much labor to keep them in order, 

 they do not remove the water so thoroughly as do tile drains, 

 and they not only occupy a considerable area but they inter- 

 fere with the cultivation of much land on account of the 

 space along the ditches required for turning the teams in 

 cultural operations. Only under exceptional conditions may 

 open ditches be profitably used instead of tile drains. 



102. Tile drains. — These drains are composed of baked 

 clay or hardened concrete cylinders with open ends, their 

 length being about one foot and their diameter varying 

 from three inches to eight or more. These tiles are laid 

 end to end on the bottom of ditches two to four feet in depth, 

 having a fall sufficient to carry off the water and prevent 

 the tiles from becoming clogged with soil particles. Tile 

 should not be made of clay that contains particles of lime, as 

 the lime when baked is converted into quicklime, which 

 causes the tile to crumble when buried in the soil. 



It is not necessary that tile shall be permeable to water, 

 as it is through the openings between the ends of the tile 

 that water enters, and not through the pores. Vitrified 

 tile may well be used, as they are less likely to be injured 

 by freezing than are porous tile, because expansion of ab- 

 sorbed water on freezing causes the latter to disintegrate. 



Concrete tile are often used and these may be made on 

 the farm, with forms constructed for the purpose. 



Silt and fine sand may enter the tiles through the open- 

 ings between them, and to guard against this collars are 

 sometimes placed over the joints, but with proper grades 

 this is not necessary. Sometimes tile are hexagonal on the 

 outside, for the purpose of preventing settling of the tile 

 in places, with a consequent stoppage with silt. However, 

 if the bottom of the ditch is carefully made, round tile are 

 not likely to deviate from alignment and they are more easily 

 laid. 



