MANURES. 269 



It can readily be understood that cultivators are willing 

 to transport the richest qualities at considerable expense 

 while others will not bear the cost of being carried any 

 great distance. When brought into contact with water, 

 the material rapidly crumbles down. 



Natives remove the tafia from the surface where it is 

 rich and called u hamed" leaving what is poor or "berd." 

 After being left a certain time they return to the original 

 place and again remove the surface, which has now been 

 changed from "berd" to "hamed," by the bringing up 

 of salts from below by capillary attraction. 



It seems, according to investigations made some years 

 since, that, quarrying in bulk at a distance of not more 

 than a few kilometres from the river, it would not be 

 possible to obtain material possessing a greater average 

 nitrate content than 5%. It is seen therefore that the 

 material known as tafia, arid used so extensively in the 

 southern provinces of Upper Egypt, is really nitrate of 

 soda in an impure form, mixed with varying quantities 

 of clay and limestone. In addition, other salts are 

 present, viz : common salt and sodium sulphate ; this 

 however will be referred to later. At the time when the 

 question of the use of tafia was causing considerable 

 discussion, the possibility of profitably extracting nitrate 

 of soda in a pure form was discussed, it being thought 

 by some that the pure salt could then be used by culti- 

 vators without having to transport such a great bulk of 

 useless material at the same time. The question of being- 

 able to export nitrate was also considered. 



