84 



THE DATE PALM. 



TABLE 17. Per cent of alkali soluble in excess of water in surface crusts from Fougala, 



Algeria. 



1 Mr. Seidell's original analysis of this surface crust is as follows: 



The crust from Station No. 4 shows less than half as much common salt (sodium 

 chlorid), but four times as much Glauber's salt (sodium sulphate) as that from 

 station No. 1. 



ALKALI CONDITIONS IN RELATION TO DATE CULTURE AT CHEGGA, ALGERIA. 



In traveling southward from Biskra one follows near the course of the Biskra Kiver, 

 and passes occasional areas covered with bushes and small trees, which doubtless 

 get scanty supplies of water by seepage from the subterranean flow in the river. 

 After crossing the Oued Djedi (see map, PI. II, p. 76), which is the principal artery of 

 surface drainage of the Algerian Sahara, but which is usually entirely dry, the Small 

 Desert of Morran is entered, a region almost entirely devoid of vegetation. At about 

 30 miles south of Biskra the "bordj " of Chegga (see map, PI. II, p. 76) is reached. 

 Chegga is about 22 meters (72 feet) above sea level, and is only about 8 miles from 

 the Chott Melrirh, a salt lagoon nearly dry, which is here some 90 feet below sea 

 level. Samples were secured of the water from a flowing artesian well which irri- 

 gates the little group of palms near the bordj, and which in spite of its bad quality 

 is used for drinking and for cooking purposes. 



About a mile to the eastward and at a somewhat lower level is a date plantation of 

 some size, the property of a French company. Here samples were secured of the 

 artesian water used to irrigate this plantation. Analyses are given herewith of the 

 water of the two artesian wells at Chegga, made by Mr. Seidell, and also the analysis 

 by Carnot& (of the Ecole des Mines, Paris) of the water from the Bir Djefair well, 

 some 6 miles north of Chegga. 



A bordj is a fortified shelter for travelers, such as is common in Algeria. 

 & Holland, Hydrologie du Sahara, p. 294. 



