124 THE SAHABAN STEPPE. 



markable region, divides it into three distinct sub-regions : the 

 Desert of the Table-lands, the Desert of Erosion, and the Sandy 

 Desert* 



In Algeria, and in Barbary generally, the Mediterranean littoral 

 does not come into immediate contact with the Sahara ; but is 

 separated from it by the Atlas chain. But the Atlas does not rise 

 abruptly from the plain : on either side it ascends by a succession of 

 rocky steps or terraces, which form the sub-region of the elevated 

 Table-lands. Vast denuded surfaces, sprinkled with ckotts, or salt 

 lakes, deprived of all arborescent vegetation, traversed in summer by 

 immense herds which feed on the plants even to their very roots, bare 

 mountains starting abruptly from these horizontal surfaces ; such is 

 the general aspect of the landscape. The richly-varied culture of the 

 Mediterranean littoral has disappeared, and barley is the only cereal 

 which the husbandman relies upon for his harvest. At many points, 

 however, the " purple vine " and " golden olive " succeed admirably, 

 and are destined one day to clothe the nakedness of these plateaux 

 which the free-pasturing herds and the careless Arab have stripped of 

 their blooming verdure. 



Descending these rocky terraces of gray old Atlas, we enter the 

 desert region in its first phase : the Desert of the Table-lands, or 

 Saharan Steppe. 



Here, horizontal strata of mud and gypsum, or sulphate of lime, are 

 deposited upon the shores, as it were, of the great Sandy Sea. The gyp- 

 sum reposing on the mud is composed of plates in such close juxtaposi- 

 tion as to resemble an artificial pavement. "It covers the surface of vast 

 plateaux which have not been encroached upon by the waters; whether 

 those waters were marine currents at the epoch when the Sahara was 

 a vast sea, or diluvian torrents which descended from the mountains 

 after their elevation, little matters ; the gypsum, produced by the 

 violent evaporation of the Saharan sea, has withstood their operation, 

 and composes the plateaux of which we are speaking. Their surface 

 is so smooth, that vehicles might roll for leagues upon this natural 



* M. Charles Martins, " Du Spitzberg an Sahara" (Paris, 1866), pp. 555, et sej. 



