APRIL— JUNE, 1857 ] Meinoir 07i the Aden Reservoirs. 33 
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 intJ 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 prjved 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, &cc. 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 - 
