THE DRAINAGE OF FARM SOILS 227 



and over the tiles, care being taken not to move 

 them out of line. 



The remainder of the ditch is filled very rapidly 

 in any way that is handiest. An ordinary scoop 

 scraper may be used if the team is hitched to it by 

 a long chain and works on the opposite side of the 

 ditch. Sometimes the ditch may be filled most 

 economically entirely by hand. A wooden scraper 

 shaped like a snow plow drawn backward is some- 

 times serviceable for filling a ditch when the soil is 

 mellow. A road scraper is very serviceable for 

 finishing the filling after the ditch is nearly closed. 

 It is well to tramp the soil several times in the 

 process of filling. Leave the soil around the ditch 

 rounded, for it will settle. It is not absolutely 

 necessary to fill in the subsoil first and the surface 

 soil last, but this should be done as far as is 

 convenient. 



OBSTRUCTIONS IN TILE DRAINS 



If the grade is too flat to carry off the water 

 before the sediment in it settles, or if any tiles are 

 displaced, the drains may soon become partially 

 filled with soil. This is especially likely to occur 

 when the subsoil is clay. The time of greatest 

 danger is the first two years; after that the soil 

 becomes compacted about the joints. It is some- 

 times necessary to dig up poorly laid tile drains 

 every three or four years and clean out the mud in 

 them. When the fall is sharp and uniform, and 

 the joints well made, there ought not to be any 

 trouble from this source. 



The filling of tiles by the roots of trees is another 

 possible cause of trouble. These often enter the 

 joints and fill the interior of the tiles with a dense 



