40 THE HANDBOOK FOR PRACTICAL FARMERS 



in such soil the water mostly moves over the surface or through 



the upper soil and will thereby reach a shallow drain more 



readily than a deep one. 

 "V^Tien a tight soil underlies a porous soil within three or four 



feet, the best position in which to place the tile is at the junc- 

 tion of these two materials. A 

 shallow trough in the hard mate- 

 rial in which to lay the tile should 

 be formed if the tile would be less 

 than three feet from the surface 

 of the land. 



"Wherever the subsoil has tough 

 cla}^ properties, it should be dried 

 before it is returned to the trench. 

 A hardpan quality of soil should 

 not be placed on the tile if a 

 porous top soil is reasonably 

 available. 



Loose sandy land, if wet, re- 

 sults from some pocket or ob- 

 struction in the subsoil. The 

 drains should be placed at a me- 

 dium depth of three to four feet, 

 since the water table rises in the 

 soil until it reaches the level of 

 the drain. Often a rim of tough 

 soil will be encountered which 

 may be primarily responsible for 



^e-. 



^ 



JZ 



fiG. 17. — Sketch showing a system of 

 drainage by which the area of 

 double-drained land is reduced to 

 a minimum. — U. 8. Dept. of Ag- 

 riculture. 



the wetness of a large area. 

 Drains may be from five to ten 

 rods apart, depending on the na- 

 ture of the soil. 



In muck soil drains should be 

 from three to four feet deep and 

 from fifty to one hundred feet 

 apart. Tile placed shallow may be uncovered by the shrinkage 

 and decay of such soil. 



On slopes and hillsides that are uniformly wet, nearly the 

 same arrangement should be followed as on flat land. It is 

 usually best to run the drains up and down the slope. 



Where local springy places and wet hollows occur, they should 

 be reached by the most direct course. Sometimes this condition 

 is combined mth general wetness, and the two sets of principles 



