IX.] IRRIGATION NECESSITATES DRAINAGE 249 



Nile banks, was protected by insignificant dykes, which 

 dykes were burst every very high flood, and thus allowed 

 to be swept over by the Nile and washed once every 

 seven or eight years. All this is at an end now in 

 the tracts under perennial cultivation, and other remedies 

 have to be found." 



The only remedy for the evils attending irrigation 

 is the introduction of drainage channels at a lower 

 level than the canals bearing the irrigation water; in 

 this way the percolation through the soil, which in 

 humid climates naturally removes the salts not taken 

 up by the crops, is effected artificially; there is some 

 apparent loss of water, but this is absolutely necessary 

 to maintain the land free from injurious salts. As 

 an example, the following passage may be quoted 

 from one of Major Hanbury Brown's reports on 

 Egyptian Irrigation : — 



" It has been ascertained that the blessing of 

 improved water supply which has resulted from the 

 barrage having been made to do its duty, has been 

 attended in some localities with the evils due to 

 infiltration and want of drains. The remedy, as pointed 

 out in last year's Report, is to remove the want of 

 drains by digging them, and to provide the means of 

 washing out the salt brought to the surface, by infil- 

 tration in the shape of a liberal supply of water, by 

 which the salt would be carried away in solution along 

 the drains, or be forced down below the surface of the soil 

 to a depth at which it would be harmless. The liberal 

 water supply is not to be obtained except by the con- 

 struction of a storage reservoir at Aswan or elsewhere." 



It was the neglect of drainage, when irrigation 

 canals were introduced, that led to so widespread a 

 deterioration of land in Egypt. To quote from Lord 

 Milner's England in Egypt ; — 



