32 Memoir on the Aden Reservoirs, [no. 3, new series, 



A glance at the map of Aden will show, that the range of hills 

 which forms the boundary of the crater, is nearly circular, on the 

 outer or Western side, the hills are very precipitous and the rain 

 water descending therefrom is carried rapidly to the sea by means 

 of a number of long narrow valleys separate from each other. 



On the inner, or Eastern side, the hills are quite as abrupt, but 

 the descent is broken by a large table land occurring about midway 

 between the summit and the sea level, which occupies about one- 

 fourth of the entire superficies of the Peninsula. 



This plateau is intersected by numerous deep ravines, nearly all 

 converging from the Shumshum range into the Tawela valley, 

 which thus receives about a quarter of the drainage of the Penin- 

 sula. 



The steepness of the ravines, the hardness of the rocks and the 

 scarcity of soil on them, all combine to prevent any great amount 

 of absorption, and thus a very moderate fall of rain suffices to send 

 a stupendous torrent of water down the valley, which, ere it reach- 

 es the sea, not unfrequently attains the proportions of an unforda- 

 ble river. 



The damage done by this torrent has frequently been considera- 

 ble, during my residence in Aden I have seen kutcha houses, fur- 

 niture, animals, and even human beings carried with irresistible 

 velocity into the sea, and during a fall of rain which occurred at 

 midnight on the 28th December 1842, so great was the rush of 

 water that upwards of two hundred animals, were carried away, 

 and nine men were missing in the morning, only three of whose 

 bodies were ever found. 



Rain to this extent is exceptional in Aden, but few years pass, 

 during which many thousand tuns of water are not lost from want 

 of means to retain it. 



Our predecessors were more provident as the gigantic reservoirs, 

 which occur chiefly in and near the main water-course, the Tawela 

 valley, attest. 



Most travellers have erroneously described them as excavated 

 out of the solid rock, but I am not aware of any such. Those under 



