IRRIGATION AND SEWAGE FARMS 



141 



Systems of Distribution. 



I. Ridge and Furrow. — Flat and heavy soils are laid in ridges 

 40 feet apart, sloping 20 feet on either side, at an incline of 

 I in 50 to I in 150, to furrows in the centre. From a trans- 

 verse main carrier at the upper end the sewage passes into 

 distributing channels on the ridges, whence it flows in a uniform 

 layer down the slopes, any not absorbed running from the furrows 

 into a lower plot. The distributing channels (with the ridges) 

 have a longitudinal slope of i in 600 to i in 300. The main 

 carriers must be lined ; the channels may be dug in the soil. 



