LAND RECLAMATION. 205 



of it during the winter months. Before the land can 

 dry, fresh rain falls and, besides, the salt in the soil 

 holds so much moisture that land will not crack till 

 it is comparatively sweet. Cracking with fissures an 

 inch wide and eight inches deep is a sure sign of 

 sweetening. Nile alluvium when quite sweet cracks 

 in summer to a depth of several feet and the cracks are 

 three or four inches wide. Some plots sweeten very 

 slowly as the water will hardly filter through. It is 

 useful then to shut the water off a hoshay, carefully note 

 the gattas which retain water on their surface, and, in 

 every case where the surface is not dry in five days an 

 additional drain should be made up the centre of the gatta 

 dividing it into two parts with a width of 25 metres each. 

 Sweetening takes place first on the surface and alongside 

 the drains, and more slowly the greater the distance from 

 the drains. The following are actual results of estimations 

 of sodium chloride or common salt. 



AMOUNT OF SODIUM CHLORIDE (COMMON SALT) IN 

 LAND UNDER RECLAMATION. 



Depth Unreclaimed land 1st year 2nd year 3rd year 4th year. 

 15' cent. 8'17 % 117 % '212 % 29 % '15 % 



30 cent, i'.lO % 3*130 % '26 % 



Constant filtration of water through the soil infallibly 

 removes salt but from the centre of a gatta to the side 



o 



drain, a distance of 25 metres, there is a slope of the water 

 table, and therefore it is some years before the subsoil in 

 the centre at a depth of 50 centimetres becomes sweet. 

 Diffusion of liquids must however help to sweeten even 

 to depths below the level of water in the drains. 



