192 



IRRIGATION. 



mile, the ground under irrigation sloping 8 feet to the 

 mile. The dotted contour lines in the plot represent each 

 foot of slope upon the ground. The water is delivered 

 from the main canal into the primary distributing ditch, 

 at A, D, flowing in the direction of the arrow. This 

 ditch has a slope of 8 feet to the mile. From these 

 ditches it flows into the secondary ditches, A B, D F } 



J / / //. 



/ 



\ \ / \ \ \ \ V \ \\ 



V\ \\yV\\\ 



\ \ \ V\ \ \ \ V 



\\ \ \/\ \ \ \ \~A\ 

 \\ \ V \ \ \ \ \/\ 



p\\ \ A \ \ \ \ x\\ 



T 



Fig. 81. PLOT OF IRRIGATED FIELD. 



(which have a slope of 5 feet to the mile), through 

 gates at A, and D, into the catch-water ditches, J5, F, 

 from which it flows into other series of secondary ditches 

 beyond. Gates are established in the secondary ditches, 

 midway of their length, as at (7, and E. 



The subdivision of the plot is as follows : Furrows 

 made with the plow or with a ditching machine, which 

 finishes a perfect water furrow at one operation, are run 



