SALINE SOILS. 45 



In the dry season the bottom of the basin is covered with a crust of 

 suit, in some cases of suificient thickness to make its exploitation profit- 

 able. In the wet season this gives place to a shallow lake of salt water. 

 A number of such chotts occur near the coast in western Algeria. 

 The writers visited one large salt lake near Arzeu and another near 

 Oran. At the Salines d' Arzeu great ([uantities of commercial salt are 

 prepared. These chotts correspond to similar salt, soda, and ""playa" 

 lakes of Utah, Nevada, and other western States. 



Many salt lakes also occur in the high plateau region. In the eastern 

 part of the Sahara the chotts cover extensive areas south of Tunis and 

 of the Department of Constantine. There they are below sea level, 

 and the country around them is ver}- hot and dry. 



DESERT REGION. 



The saline soils of the Oued Rirh region in the Sahara, so far as they 

 were examined by the writers, generally contain a large amount of 

 gypsum, (.'■'ee p. 46. ) Sodium chlorid and sodium sulphate are the next 

 most abundant salts, while magnesium salts are present only in small 

 quantities. The Saharan soils ai'e usualh' of xeyy light texture, and 

 their proper irrigation demands large quantities of water. The water 

 used contains a high percentage of soluble matter. Consequently, 

 where proper drainage facilities have not been provided, the salt has 

 [accumulated in the soil to an injurious degree. Yet, by digging open 

 drains 8 feet deep at frequent intervals and irrigating once a week 

 or oftener, the natives of the Sahara are able to maintain gardens con- 

 taining a variety of plants not particularly resistant to salts in "the soil. 



More than this, using strongly saline water (see p. 38) the>^ are 

 able to reclaim land that contains an excessive amount of salts. The 

 writers visited a garden which had been established on the slope of 

 the bed of a salt lake, in which alfalfa, various garden vegetables, and 

 a variety of .young fruit trees were flourishing. The reclamation of 

 this piece of land had l)een accomplished in three years by irrigating 

 twice a week during that period. 



