ON DTIAINING. 



407 



Fig. IV. 



A B, Ditch 6 feet wide at surface. 



BC, do. 24 feet deep. 



CD, do. 2^ feet wide at bottom. 



A E, Dike 2| feet high, built of feal or sods, raised from the sur- 

 face A B. 

 E F, do. 2 feet wide at top. 

 W, Whin -bed on the top of the dike. 



