30 



DATE VAEIETIES AND DATE CULTURE IN TUNIS. 



unequal, the palms in some gardens being amply and even super- 

 abundanth' irrigated, while thousands of trees receive no irrigation 

 whatever, except by seepage." 



There is some indication that the flow of the springs at Tozer is 

 diminishing in volume. It would appear also that there has been a 

 gradual lowering of their level, due to the progressive cutting down 

 of the beds of the streams derived from them, and that in consequence 

 the irrigable area of the oasis is diminishing.'' 



In the oasis, or oasis group, of El Oudiane CO springs furnish the 

 water with which the gardens are irrigated. They are generally' 

 smaller than those of Xefta and Tozer, and their flow is said to be 

 perceptiblv diminishing. Their Avaters are not united to form a large 

 stream which is subsequently divided and subdivided by dams, as in 

 the oases just described, but are for the most part conducted directly 

 to the gardens. These, owing to the small width of the oasis and 

 its situation at the very foot of the terrace, are nowhere far removed 

 from the sources of supply. 



At El Hamma there are 15 springs of considerable size, one of them 

 having a temperature of 107.5° F. (42° C). To this spring, which 

 is much frequented by the natives for the sake of the hot baths it 

 affords, the oasis owes its name, which means " the bath." 



A sample of irrigating water Avas collected l)v the writer in the 

 main stream of Tozer, above the first dam which divides it. This 

 water, tested both at the moment of collection and two months later, 

 when the analysis was made, gave neither an alkaline nor an acid 

 reaction. Its electrical resistance at the time when the sample was 

 taken was 117.3 ohms at 60° F. The chemical analysis, made in the 

 laboratory of the Bureau of Soils, showed 209.2 parts of soluble 

 matter per 100,000 of water. The composition of the soluble con- 

 tents was as follows, in percentages of the total : 



Table 8. — Chemical composition of irri<jatio)i icatcr, Tozer oasis. 



Components (ions). 



Calcium 8.50 



Magnesium -- - 4.54 



Sodium 9.13 



Potassium 12.34 



Sulphions - ! 34.23 



Chlorions- 

 Carbonic acid . 



24.33 

 6.33 



100.00 



Conventional combinations. 



Calcium sulphate 28.87 



Magnesium .sulphate- 

 Potassium chlorid 



Magnesium chlorid . . 



Sodium chlorid 



Sodium bicarbonate . 



17.36 

 23.47 



4.11 

 16.68 



9.51 



100.00 



o At Biskra, in Algeria, 0.12 quart per palm per minute is found to give satis- 

 factory results, the water being retained at the bases of the trees in holes that 

 are dug for the purpose. (See Bui. 53, Bureau nf Plant Industry, p. 47.) 



6 Doumet-Adanson (ibid.) noticed old date palms at Tozer that could no longer 

 be irrigated, being no less than 40 feet above the present level of the springs. 

 92 



