136 The Control of Mosquitoes 



Where seepage outcrops on bare hillsides, or at 

 the foot of slopes where there is insufficient grade 

 for the use of tile drains, open ditches are used. 

 In these cases the water is intercepted as in the 



1 



Side View 



Junction of Two 



Tile Lines showing 



"Y Joint" and Grades. 



Plan of Junction 

 of Tile Lines 



Plan and side view of junction of tile lines. 



case of a tile ditch, but the side of the ditch nearest 

 the hill must be given flatter slope than the other 

 side, because it is wet and more apt to break off and 

 fall into the ditch. If such a ditch is expensive to 

 maintain, it should be lined with concrete, and 

 plenty of weep holes left to care for seepage 

 water. 



