2Q4 



ENGINEERING ON THE FARM 



Blinding. After the tile are laid a covering of 4 to 6 inches 

 of earth is put on to hold the tile in place. This covering 

 is called blinding, and is put on by the workman walking 

 astride the trench and cutting down the' earth below the 

 surface from either side with a tile-spade, taking care not to 



disturb the tile and batted 

 joints (Fig. 241). 



Backfilling. The refill- 

 ing of tile trenches is 

 accomplished in several 

 ways. Short sections, in 

 the vicinity of fences or 

 buildings, are filled by 

 hand, the tools used being 

 a shovel or ordinary spade. 

 Where the material is 

 soddy or sticky, a potato 

 fork or other heavy-tined 

 fork can be used to ad- 

 vantage. Coarse sod can 

 be conveniently handled 

 by a fork bent in the form 

 of a hook . Where a team 

 can be employed short 

 sections can best be filled by two men with a team and slip 

 scraper. Where there is a line of trench free from obstruction, 

 the most economical method of filling is by means of a plow. 

 Tile outlet. The action of the tile is dependent upon the 

 distance of the outlet above the surface of the water at the 

 outlet channel and not the distance above the bottom of 

 the outlet ditch. So long as the water of the outlet is below 

 the tile, the drain will act to its full depth. If the water rises 

 above the outlet, drainage will take place only above the 

 elevation of the water surface, and if it becomes higher 

 than the bottom of the swales in the area drained, water 

 will stand on the surface of such places until it falls at the 



After the University of Minnesota 



Fig. 241. Blinding tile 



