1869.] BLANFOED ABYSSINIA. 405 



Aden series of volcanic rochs. — Along both shores of the southern 

 portion of the Eed Sea and of the GuK of Aden, there is an im- 

 mense development of volcanic rocks, amongst which are many re- 

 cent and, it is said, a few active craters. These formations have been 

 described by several travellers*. 



Near ZuUa, on the west side of Annesley Bay, these beds are but 

 sparingly represented ; but all the eastern shore of the inlet consists 

 of them. Near Massowa they are better seen and consist of lava- 

 flows interstratified with beds of ashes and of sedimentary deposits, 

 gravels, and sandstones, some of which contain marine shells. 



The lava-flows diff'er entirely from all the volcanic rocks of the 

 highlands, and are assuredly of much later date. Still some of them 

 may be far from recent, the great denudation they have undergone 

 in places indicating considerable antiquity. As a rule they are in- 

 clined and present the appearance of having been much disturbed. 



Recent formations. — These are not, for the most part, sufficiently 

 important to demand much attention. Large alluvial deposits exist 

 along the coast, north of Massowa and elsewhere, which appear not 

 to be marine, but are more probably due to the washing down of 

 pebbles and sand by rain and small torrents from the hills. They 

 are frequently of considerable thickness. 



Black soil precisely similar to the " regur " of India exists in the 

 neighbourhood of the basaltic rocks on the highlands, and is pro- 

 bably derived from their decomposition. Of the plateau (Wadela- 

 Talanta) between the Takkazzye and Jidda rivers, the northern half, 

 where traversed by the British force, was of trachyte and had no 

 black soil on it ; the south consisted of basalt covered by black soil. 

 The latter, just like the Indian " regur," seemed peculiarly well 

 adapted to the growth of cereals t« 



Denudation. — The enormous gorges cut by the rivers near Mag- 

 dala attracted general attention, though they are in reality trifling 

 when compared with those of the Takkazzye and other rivers. If it 

 is correct to believe that the trappean formations once covered Abys- 

 sinia (and certainly it is difficult to escape the conclusion), then 

 from 4000 to 10,000 feet must have been removed from by far the 

 greater portion of the surface. There is not a trace of marine denu- 

 dation over the surface examined. 



Lake Aslidngi. — This small piece of water, the only one of the 

 Abyssinian lakes which it was possible to visit, lies in a small basin 

 of basaltic rocks and has no visible outlet. The perfect sweetness 

 of the waters, and the absence of any evidence of great change of 

 level, prove that a subterranean outlet must exist. It is by no 

 means clear how the rock-basin has been formed. Its form is op- 

 posed to the idea of its having been due to glacial action, and no 

 trace of the former existence of glaciers could be detected ; but it 



: * Ferret et Gralinier, ' Kocher d'Hericourt,' &c. 



t It shoiild be remembered that some Indian black soil can scarcely be 

 derived from basalt. Such is the case in the extensive deposits of the lower 

 Cauvery valley. Those who have only seen the soils of western India are 

 sometimes not aware of this. 



