Fig. 70. — Couple druna. 



Fig. 71.— Tile drain. 



Pig. 73.— Drain gauge. 



17 



Fig. 74. — System of drains on a 

 pronounoed slope. 



"^ ° ^, f ■ 1 '"^ J Fig. 76.— Section of a drain. 

 Fig. 75.— System of drains on level ground. = "' 



