42 IRRIGATION. 



the headland. The principal canal of supply for the 

 range of ridges below it will run along the crest of this 

 headland, and a canal of distribution will run along the 

 crest of each of the secondary ridges. Each headland 

 or principal ridge, with its canal, and the range of ridges 

 starting at right angles from it, each one of them having 

 its distributing canal, will then form a system of irriga- 

 tion independent of the other series of ridges. Every 

 seven of these secondary ridges, if they are 30 feet wide 

 and 210 feet long, will occupy one acre of ground. At 

 the foot of each series of ridges will be needed a draining 



Fig. 7. SYSTEM OF BEDS. 



furrow, unless the ground is underdrained with tile, to 

 carry oS the surplus water. A tile drain between each 

 pair of beds or secondary ridges would be the best method 

 of drainage, and the supply of water should be regulated 

 so that the whole is absorbed and none is allowed to flow 

 away unused. The tile drains are shown at , #, a, fig. 6. 

 The series of beds and canals will then appear as shown 



