182 



EGYPTIAN AGRICULTURE. 



it can lift. Unless the back is shrouded in, the excess falls 

 back over the float and much work is lost. The same 

 thing happens with too high an outfall channel. 



The Atfeh scoops are 10 metres in diameter, 3*60 m. 

 wide, make 1 J revolution per minute and can discharge 

 300 cubic metres per minute at 2*50 m. lift. 



Scoop wheels need very heavy and expensive foundations 

 and are not likely to be again erected in Egypt. Small 

 ones on 1 to 1 J metre steady lift, driven by windmills, 

 might possibly be adopted in the Delta along the coast. 



Centrifugal Pumps. These are the best all round 



Fro. 59. CENTRIFUGAL 



machines and the only ones with any elasticity of lift 

 when there is variation of intake or outfall levels. 



