PHYSICAL GEOORAFHY OF ABYSSINIA. 153 



former underlying the latter. The limestone alone is 

 fossiliferous, and is of Jurassic age. 



The country below the mountains along the Eed Sea, 

 inhabited by the Danakil, Somali, and Galla tribes, is 

 but little known, and no opportunity was afforded to me 

 of penetrating into it during the progress of the expedi- 

 tion, the only exploration made, that of Colonels Phayre 

 and Merewether, in the direction of the Alelbad Salt 

 Lake, having been accomplished before my arrival at 

 ZuUa. The region appears to consist of transverse 

 (E. and W.) chains of hills, separating desert tracts, 

 many of which are below the sea-level, and some of 

 which may formerly have been parts of the sea subse- 

 quently cut off and dried up. Water is scarce, the rain- 

 fall being scanty, and aU brought down from the hills by 

 streams appears to be evaporated. Along the coast of the 

 Bed Sea there is a belt of volcanic rocks of very late 

 geological age, the elevation of which may have cut off 

 such tracts as the salt plain west of the Amphila and 

 Lake Assal west of Tajurra, both of which are below the 

 sea-level. 



This belt of volcanic rocks is extremely narrow in the 

 neighbourhood of ZuUa and Massowa. A few observa- 

 tions of interest were, however, made upon it, which will 

 be found hereafter. Before concluding this brief sketch, 

 there are two points connected with the physical geo- 

 graphy of Abyssinia of which some notice should be 

 taken. These are the evidence of denudation afforded by 

 its surface and the conditions under which the only lake 

 examined occurs. Both are subjects of considerable interest. 



