SAHARA 207 



of a delicate greyish-green. Desultory bushes of leafless 

 retama, buried and then uprooted by the wind, of 

 Saharan broom, tufts of drinn-grass, spurge, and 

 some other dry undershrubs and grasses are scattered 

 over the sand. Farther on, the dunes may be partially 

 or temporarily fixed by the binding aristida, and the 

 tamarix endeavours to form a thin heath. 



These three main varieties of the Sahara appear to be 

 distributed in vast areas or regions which they may 

 serve to characterize. Thus the westernmost or coastal 

 band, including the Rio de Oro and Sahel and extending 

 down to Senegal, is chiefly one of hamadas and aregs : 

 a second region, stretching from Tunis to the western 

 Aderar, includes the Great Erg, the Igidi and Elgof, 

 and is a colossal sea of sand-dunes : to the east, a 

 broad expanse of hamadas and aregs characterizes the 

 somewhat higher plateaus of Ahaggar continued south- 

 ward by that of Ahir; and is followed again by the 

 somewhat interrupted and lower ergs of the Fezzan and 

 Teda. The central portion, reaching south to the Chad 

 and embracing the Tibu with the Tibesti range, is 

 mostly hamada and reg. The Libyan desert, beyond 

 the oases of Farafreh, El Khargeh, and Dakhel, is one 

 vast unbroken stretch of dreary barren sands. In the 

 Egyptian and Nubian deserts is shown a recurrence of 

 the rocky and clayey, hilly type divided or interrupted by 

 the narrow valley of the Nile or Egypt proper. Beyond 

 the Red Sea again, the Arabian desert is divided into 

 vast seas of moving sand and wastes of stone and lava. 



The saline tracts characteristic of all deserts are 

 always present in the Sahara, with their usual vegetation 

 of fleshy or * succulent ' salt-bushes. As may be noticed 

 on the maps, the caravan routes avoid the ergs and go 

 from well to well, and from oasis to oasis, over and along 



