APRIL — JUNE, 1857.] Memoir on the Adeii Reservoirs. 35 
flows ; it was very much destroyed, one wall having been forced in, 
either from the pressure of water from without, after the tanks and 
aqueducts above it became ruins, or by the water finding its way in- 
side the masonry and sapping its foundations. It has however 
been repaired, and I am sanguine that it will prove water-tight. 
Thus far only the series is complete, beyond, the main aqueduct 
has not been finished, though it is in course of construction, and 
the other tanks, which are finished, have not been united. 
One of the most remarkable is No. 11, which is a double tank 
situated below a deep rift in the hill, down which a great volume of 
water flows, but as if to make sure of its being filled, the drainage 
of the hill side behind it, is conveyetj into it by an aqueduct lead- 
ing through a small hole in the rock, not larger than a man's head. 
The entrance to this tank was originally domed, and contained an 
inscription which has been removed, the dome has been restored. 
The other tanks which have been restored, require no notice. 
Appendix B is a statement of all the remaini'ag reservoirs which 
have been discovered, some of them are cleared out and nearly com- 
pleted, others are in course of restoration, the rest have not been 
commenced : of these immeasurably the finest is that marked I. It 
is nearly a cylinder of one hundred and forty-eight feet in diameter 
but the depth has not yet been ascertained, about twenty-four feet 
have been cleared out, but the bottom has not been reached : into 
this reservoir, the overflow of all the tanks from No. 1 to 10, in table 
A and from A toH in Table B and probably several others, will meet. 
It may be imagined that in so arid a spot as Aden, so many tanks 
are useless and can never be filled, but I have known many falls of 
rain during my residence here, which would have filled them all, 
and many more had they existed. 
I regret that I am unable to delay the printing of this memoir, 
until a plentiful fall of rain, which may be expected about this sea- 
son, shall have tested their value. » 
But whether they all prove water-tight or no, it is hardly possible 
to over estimate the value of these reservoirs in a place like Aden, 
which with a population of 25,000 souls, has a daily supply of sweet 
water not exceeding 15,000 gallons. 
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