20 MALLET: ADEN AND VICINITY. 



Wherever I obtained well sections in the plain between Aden and 

 the foot of the sand hillsj there was more or less silty alluvial soil at the 

 surface, amounting in thickness to a few feet at Shaik Othman, but at 

 Majhafa and thereabouts, to 20 or 30. Between the cultivated lauds 

 are large patches of sand, and I am not certain whether the alluvial soil 

 is continuous over the whole plain, being covered over and concealed in 

 places by blown sand, or whether it is absent in some localities : but I am 

 inclined to believe that it is continuous. 



Beneath the surface soil is sand passing downwards into gravel, the 

 whole being stratified horizontally or more probably having a .gentle dip 

 towards the sea corresponding with that of the plain. To the north are the 

 blown sand hills, which rise 600 or 800 feet from the plain to the foot of 

 the hills, and which have been produced by the latter acting as a sort of 

 ' dam' tothe current of sand carried along by the south-west monsoon. 

 There can be no doubt that the sand here is several hundred feet deep. 



Although there is abundance of excellent water stored up in the 



stratum of sand and gravel beneath the plain, it is 

 Artesian wells. ,„., , ., , t • ^ 



sell evident that such water cannot be obtained by 



means of artesian wells, for the very simple reason that the wells from 

 Shaik Othman to Lahej are sunk down to this water-bearing stratum, 

 and that the water does not rise above it. Even supposing the hydros- 

 tatic conditions to be otherwise favourable, there is no impervious 

 stratum above the gravel bed. The surface alluvium is always more or 

 less sandy and could not keep the water down were it inclined to rise ; 

 that it does not do so is clear from the fact of all the existing wells 

 piercing through it. 



The only chance therefore for an artesian boring lies in the 

 possibility of an impervious stratum existing beneath the gravel bed, 

 and under that again a second water-bearing stratum. I have no means 

 of forming an opinion as to how deep the gravel bed goes, but 



from the increasing coarseness of the materials in descending, and^the 

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