April— june, 1857.] Memoir on the Aden Reservoirs. S3 



the foot of the hills are generally built at a re-entering angle of the 

 rock, which promises a copious flow of water, here the soil has been 

 carefully cleared away and a salient angle or curve of masonry built 

 across it, while every feature of the adjacent rocks has been taken 

 advantage of, and connected by small aqueducts, to ensure no water 

 being lost. 



The overflow of one tank is conducted into another, and thus I 

 believe that a complete chain existed into the very centre of the 

 town, where small tanks which could not otherwise be filled, are 

 being daily discovered. 



Their construction is extremely fantastic, the only principle which 

 seems to have been adhered to, is the avoidance of straight lines, 

 and the wisdom of this has been proved in the recent excavations, 

 as in almost every instance where a straight line has existed, it has 

 been forced in by the rush of water without it. 



They are generally of stone and mud masonry, roughly plastered 

 on the outside, and beautifully coated in the interior with chunam ; 

 flights of steps, gradients, platforms, &c. are heaped together and 

 give an exceedingly grotesque appearance to the whole : each large 

 tank has a smaller one in front of it, built for the purpose of retain- 

 ing all earth and stones carried down by the torrent, and permit- 

 ting a pure stream of water to flow into the reservoir beyond. 



As before mentioned, the majority of the tanks are in and near 

 the Tawela valley, which intersects and receives the drainage of 

 the large table land under the Shumshum range. This valley is 700 

 feet in length from the point where it leaves the table land, to its 

 actual junction with the level plain of the crater. The hills through- 

 out its entire length are perpendicular, and at the head of the val- 

 ley they meet, leaving barely sufficient room for one man to pass. 

 The valley then gradually opens out, and at the gorge, it is one 

 hundred and fifty feet in breadth, the hills then circling round to 

 the right and left, form part of the walls of the crater of Aden. 



Appendix A is a tabular statement of the various tanks which, 

 together with the aqueducts leading to them, have been thorough- 

 ly repaired and are now ready to receive water. 



No. 1 is at the top of the valley just described, and is formed by 

 a wall dra>yn across it, connecting the hills on either side, precise- 



