ALKALI CONDITIONS AT OUKLANA. 



91 



The well Puits Desveaux from which the plantation was irrigated, yields an 

 abundant supply of very alkaline water. Mr. SeidelFs analysis is as follows: 



TABLE 24. Composition of artesian water (Puits Desveaux) used to irrigate date plantation 



at Ourlana, Algeria. l 



*Mr. Seidell's original analysis of the artesian water of Ourlana is as follows: 



In contrast to the water of Chegga (see p. 85), having almost the same amount of 

 dissolved salts, in which the sulphates predominated, the chlorides are here in excess, 

 constituting 52 per cent of the total dissolved salts, while the sulphates make up 

 46.83 per cent. The average of 26 analyses of the water from flowing artesian 

 wells in the Oued Rirh is given by Holland as follows: 



TABLE 25. Average composition (in percentage by weight) of 26 samples of artesian water 

 from the Oued Rirh, Algeria. 



Sulphates 0.25436 



Chlorids 21279 



Carbonates 01257 



Nitrates and dissolved organic matter 00411 



Silicates and suspended matter 00310 



Total....; 48693 



It will be noticed that the sulphates preponderate over the chlorids in this table, 

 though not so much as in the Chegga water. 



Station No. 1 at Ourlana was near the bordj and not far from the well. Young 

 and old date palms were growing near by in good condition. There was an open 

 drainage ditch near by, but this did not prevent the formation of a surface crust of 

 alkali. At 36 inches below the surface water was found, and below that level the 

 sand was very wet, resembling quicksand. 



Holland, Hydrologie du Sahara, p. 260. 



