24O THE FIRST BOOK OF FARMING 



heavy soils to over two hundred feet in light soils. 

 The usual depth is about three feet, though the 

 farther apart the deeper they are put. 



A lateral tile drain should enter a main at an 

 acute angle to prevent too great a check in the cur- 

 rent. 



In putting in a drainage system the first thing to 

 be done is to make a plan of the ground and deter- 

 mine the slope of the land and the grade of the 

 drain. The ditches are then staked out and the dig- 

 ging proceeds. In digging the ditches plows are 

 sometimes used to throw out the top soil, then the 

 work is finished with spades and shovels. 



Professional ditchers use special tools and they 

 take out only sufficient earth to make room for the 

 tiles (Fig. 85). The tiles are then laid end to end, 

 the joints covered with a piece of sod, some grass, 

 straw, paper or clay, to prevent loose soil sifting in. 

 As the tiles are laid, enough soil is placed on them 

 to hold them in place until the ditch is filled. 



In laying the tiles an even grade should be main- 

 tained (Fig. 86). A lessening of the grade checks 

 the current of water and tends to cause a stoppage 

 of the, drain. 



The water gets into the drain through the joints 

 where the tiles come together. 



The, outlet of a tile drain should be protected by 

 brick work or should be of glazed tile such as the 

 so-called terra-cotta tile, to prevent injury by frost. 



The mouth of the drain should be protected by a 

 screen of wire to prevent the entrance of rats and 

 other small animals. 



