LAND DRAINAGE PRACTICE. 



45 



smaller tile instead of one large main through the cen- 

 tre. It is sometimes necessary to diverge the lines 

 toward the head, making two systems, and running 



Fig. 6. — Gridiron System. 



laterals into each from both sides. In draining hill- 

 sides and wet slopes it is best to lay lateral drains down 

 the slope, at such intervals as are required, discharging 



^ 



Fig. 7. — ^Double-main System. 



into a collecting-drain. In such cases have the collect- 

 ing drain near the base of the slope, that the laterals 

 need not pass through a flat bottom, which would re- 



