25o CAUSES OF FERTILITY AND STERILITY [chap. 



"But perhaps the worst feature of all was the 

 neglect of drainage, which was steadily ruining large 

 tracts of country. Even where drains existed, they 

 were frequently used also as irrigation channels, than 

 which it is impossible to conceive a worse sin against 

 a sound principle of agriculture. In some cases these 

 channels would be flowing brimful for purposes of 

 irrigation, just when they should have been empty 

 to receive the drainage water. Elsewhere the salt- 

 impregnated drainage water was actually pumped back 

 upon the land. 



" It was the want of drainage which completed the 

 ruin of the Birriya, that broad belt of land which 

 occupies the northern and lowest portion of the Delta, 

 adjoining the great lakes. There are upwards of 

 1,000,000 acres of this region, now swamp, or salt 

 marsh, or otherwise uncultivable, which in ancient 

 times were the garden of Egypt." 



It has been the business of the English irrigation 

 officers since the occupation to restore and improve 

 the drainage system, and to begin the reclamation of 

 the salted areas by cutting drainage canals and passing 

 enough of the abundant winter flood water through 

 the soil to wash out the salts into these drains. 



Hilgard in California has also indicated that it is 

 impossible to wash the salts from the soil, even by 

 leaving the water to stand upon the surface for some 

 time, unless provision is made to remove the salted 

 water by underdrainage. In the case of black alkali, 

 however, the soil has become too impervious to 

 allow water to percolate at all; the first remedial 

 measure is to incorporate considerable quantities of 

 gypsum with the soil ; this will interact with the 

 sodium carbonate, producing sodium sulphate and 

 calcium carbonate, at the same time precipitating the 



