DRAINAGE 2OI 



perpendicular and near together, is an advantage in 

 enabling the spademan to work loose his spadefuls of 

 earth. 



Figure 87 shows the movements of rainwater in its 

 course into the tile drain. The curved line, T-T, repre- 

 sents the surface of the zone of ground water. Above 

 this, the rainwater is represented by the dotted lines as 



percolating directly downward. 

 When it reaches the surface 

 of the standing water and adds 

 to its height, the ground water 



is a surprisingly useful tool in open- n . . , . 



ing tile or open drains in many easily floWS faster SldCWlSC toward 

 worked soils. By turning it at an . . . , 



angle as shown in Figure 93 the bot- the tlleS, which are SO laid aS 

 torn of the ditch may be made as 



narrow as desired for a 3 or 4-inch ^-Q allow it tO flow between 



their ends and flow away 



through the tiles, and thus prevent the ground water 

 rising higher and smothering the roots of the plants. 

 In case of a very heavy fall of rain, the ground water 

 accumulates more rapidly than it can seep sidewise to 

 the tiles, or possibly is in such quantity that the tile can- 

 not carry it all off, even though running full. The line X 

 shows how the water rises be- 

 tween tiles laid at intervals of 

 several rods apart. The posi- 



. 



tion of the lower curved line * ^^S, ^ST^tS. f S 

 and the water within the tiles [J* eS^better^ 6 ' Flgure 90/ handle8 

 illustrates the fact that the 



water passes into the lower half of the tile and that it 

 can seep in through the openings between the ends of 

 the tiles, not needing to pass through the walls. 



In Figure 93, A shows the manner of sinking the spade 

 in taking out the successive courses in opening a tile drain 

 by hand in a free soil. B, C, D, E and F represent suc- 

 ceeding courses. By thus "racking" the spade, each block 

 of earth is broken loose from the side, leaving a square, 

 even bank. Since only one side is broken loose and that 



