34 TUNISIA 



not one spring but from fifty to a hundred or more at the per- 

 imeter of the oases. Therefore, any system of protection 

 against sand, however costly, is fully justified because of the 

 value of the property to be protected. 



The work of protection was commenced in 1885, and, accord- 

 ing to an official statement, 14 2139 hectares (5285 acres) have 

 been placed under control at the following oases: Gabes, 76 

 (187 acres); Tozeur, 539 (1331 acres); Nefta, 426 (1052 acres); 

 El-Hamma, 98 (242 acres); El-Ouidan, 180 (444 acres); and 

 Nefzaona, 8201 hectares (20,264 acres). Up to January i, 1911, 

 the cost of this protection had aggregated 465,000 francs 

 ($89,745). Labor is paid from 1.20 to 1.30 francs ($0.23 to 

 So. 2 5) per day of 10 hours. 



Sand Drifting from a Distance. Where damage results 

 through sand drifting from a distance it may be assumed at 

 once that the direction of the wind is uniform. To prevent 

 such damage, when there is a sufficient open area in front of the 

 oasis, sand dams are built some 300 metres (328 yards) from 

 the edge of the cultivated land. While in theory this outer line 

 of defense should be as far away as possible, in practice the dis- 

 tance is usually curtailed by the character of the ground, or by 

 the extra expense of erecting a longer line of defense due to a 

 greater circumference. Often, too, the construction material, 

 as palm branches, for example, is limited, since it must be secured 

 locally. 



A second or third line of defense may be necessary to stop the 

 sand which blows over the first wall. The area between this 

 wall and the fields is closed to entry and caravan roads are 

 fenced to confine travel to the least possible area. These areas 

 are enclosed by sand walls 0.80 of a metre (31 inches) high topped 

 by a close palm branch hedge 0.40 to 0.50 metres (16 to 20 inches) 

 high and buried 0.25 to 0.30 metres (10 to 12 inches) in the ground. 

 This is the standard fence at the Djerid oases. It must be 

 repaired at least once a year and always after severe storms. 



The best time to build these sand fences is when the sand is 

 moist, so that it can be packed hard to prevent its being drifted 

 14 Based in part upon a description in the Indicateur Tunisien, 1912. 



