LAND DRAINAGE 649 



is cleaned out with a round-pointed shovel, and the bottom 

 is finished to a smooth, perfect grade by means of the 

 grading scoop, which also rounds the bottom of the trench 

 into shape to receive the tile. (See Fig. 66.) Care 

 should be taken not to excavate the trench below the 

 grade line, so that the tile may have a firm bed. 



Horse and engine power are now very generally applied 

 to trench digging. Several types of plows drawn by 

 horses are available to loosen the soil, and some types 

 are arranged to follow the grade and to elevate the loose 

 earth out of the trench. Several types of engine-driven 

 machines are in use where the land is not excessively 

 stony. They cut the trench to the full depth at one 

 operation, and are constructed so as to follow a perfect 

 grade, so that tile may be laid as fast as the machine 

 progresses. 



551. Laying tile. — Where two lines of tile join they 

 should come together at an acute angle, forming a Y 

 so that the two streams of water will have the minimum 

 interference and the collection of sediment will be pre- 

 vented. If the lines are arranged at right angles, one of 

 the strings may be turned down grade in the form of a 

 curve in the last rod of its course, to make the proper 

 union. Junction pieces or Y's may be bought in the 

 smaller size of tile. They are rated by the diameter of 

 the lateral and main branches ; for example, a 3 X 6 

 junction indicates a three-inch lateral and a six-inch 

 main. A lateral tile should enter the main drain with a 

 slight drop. A small tile should enter a larger main 

 drain at the horizontal center of the latter. 



The tiles are placed in the trench by hand, or, if the 

 trench is deep or the tiles are very large, by means of 

 some mechanical arrangement such as a hook. Their 



