PLAIN NOllTH OF ADEN. 19 



with mai'iue shells and coral, and bears unmistakably the appearance 

 of having- been a recent recovery from the sea; that the sea has g-reatly 

 receded even within the limit of history, is proved by the position 

 of the ancient seaport of Mooza, formerly one of the principal emporia 

 of the trade of Yemen, but now situated twenty-three miles inland, 

 north of the modern city of Mokka. In like manner, Ghalifica, the 

 port of Zebeed, Okelis and many others along the coast of the Eed Sea, 

 have filled up and been deserted.^'' I do not know whether there be 

 any evidence or not to prove a gradual elevation of the coast at Aden, 

 which would in itself, of course, cause the shoreline to recede from 

 the hills, and enlarge the area of the plain. There can, however, 1 

 think, be no doubt that the materials of which the plain is formed, 

 have been brought down from the interior by the rivers in the ordinary 

 manner of delta formation, and that they are not the result of degrad- 

 ation of the hills by the sea itself when the land stood at a lower 

 level, although the sea may have had some efiiect in sorting them 

 perhaps. The southern flanks of the hills, where I had an opportunity 

 of examining them, are of stratified rocks, and I believe that they are 

 formed of such all along here. It is on these, it would certainly appear 

 that the action of the sea would expend itself, but the pebbles in the 

 conglomerate beds are all volcanic and metamorphic. It might be 

 expected that as the rivers flow last through stratified rocks, the pebbles 

 brought down by them would consist chiefly of such, but such is not 

 the case. Thus in the Hassan River two or three miles below Ulkhour, 

 where it leaves the hills, pebbles and boulders from the interior, of 

 metamorphic and volcanic rocks, up to a foot in diameter are abundant, 

 but those of limestone, &c., are rare and small sized. 



A sketch section from Aden to Lahej and thence northwards to the 

 hills is given on Plate B. I do not know what the exact elevation of 

 Lahej above the sea may be, but it is very small and no doubt exagger- 

 ated in the section. . 



( 275 ) 



