24 MALLET : ADEN AND VICINITY. 



winds. Easterly winds during the north-east monsoon from the middle of 

 October till the end of March. During April and May variable winds and 

 calms. It seems that there are usually not more than two months of calm 

 in the year^ there being generally more or less breeze for the remaining 

 ten. Other power would have to be provided for the periods of calm, 

 and for such other times as the wind might not be sufficiently powerful 

 to raise a full supply of water. The following table shows the engine 

 power (working 18 hours a day) required to raise 600,000 gallons per 

 diem, which taking the population of Aden at 30,000 would allow 20 

 gallons per day per head : — 



Height raised wa?eiMe^1l"It Horsepower. 



™ ^^^^- Mahilla.* 



60 9 • 101 



70 19 11-8 



80 . 29 13-5 



90 39 15-2 



100 49 16-9 



In fixing upon the site on which to sink a well, the nearest point 

 to Aden should be chosen at which it could be sunk sufficiently deep to 

 yield the required supply, without producing any trace of brackish ness 

 in the water obtained. The nearness to Aden would be important not 

 only on account of the shorter length of aqueduct or piping required, 

 but of the lesser depth of the water-level from the surface, and conse- 

 quently the reduced pumping expenses. I believe that at Mahilla, 

 about 19 miles from the cantonments, the two conditions of sufficient 

 supply and complete freedom from brackishness can be obtained, and 

 probably nearer, but kow mucli nearer, I am not prepared to say. This 

 point ought, however, to be investigated by means of trial borings, 

 before entering on any permanent works. Such borings ought to be 



* In one well wlilcli I measured at Mahilla, the water stood at 53 feet from the surface, 

 but it was being drawn on at the time for irrigation. In another, out of work, the water- 

 level was 51 feet from the surface. 



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