376 Messrs. Play fair and Letourneux on the 



Regular as is the general character of the High Plateaux, 

 they still present several anomalies. On the southern border 

 the lower terrace, instead of forming a basin, presents here 

 and there slopes, down which the water flows to the north, 

 and thus becomes the sources of several rivers in the Tell. 



Towards the centre the basin of Sersous, filled of old by a 

 vast lake, the traces of which are plainly visible, is now 

 drained by the river Ouassel, which has forced itself a passage 

 near Boghari, between the excavated plateau of Sersous and 

 the foot of the last mountains of the Tell. On quitting the 

 High Plateaux, this river becomes the Chelif, the most im- 

 portant in Algeria. 



Towards the south-east the basin Avhich ought to have 

 existed is replaced by the immense mountain of Aur^s, of 

 which the central peak attains an altitude of 7800 feet. This 

 protuberance takes the place of a depression ; and instead of a 

 salt lake, we find a mountain covered with cedars and alpine 

 vegetation. On the north, Aur^s has only moderate slopes, 

 which convey its waters into Chotts of the neighbouring pla- 

 teau. Towards the south it is prolonged almost in a straight 

 line, and descends like a precipitous wall to the Sahara, which 

 stretches at an immense distance below it. 



In the west of Algeria the centre of the country bristles 

 with mountains, which adjoin the great snowy range of Deren. 

 The southern slopes give rise to immense rivers, amongst 

 others the Oued Grheir, which the French expedition under 

 General Wimpffen reached in the spring of 1870, and which, 

 in their admiration, the soldiers compared to the Meuse. 



Popular belief pictures the Sahara as an immense plain of 

 moving sand, dotted here and there with fertile oases ; and the 

 old simile of the panther's skin is still with many an article 

 of faith. A few details are necessary to dispel this poetical 

 but false idea. 



The desert in Algeria consists of two very distinct regions, 

 which we shall call the lower and the upper Sahara : — this a 

 vast depression of sand and clay, stretching on the east as far 

 as the frontier of Tunis ; that a rocky plateau, frequently at- 

 taining considerable elevation, extending on the west to the 

 borders of Morocco. 



The former comprises the Ziban, the Oued Ghir, the Souf, 

 and the Choucha of Ouargla, On the north it is bounded by 

 the mountain-range of Aurfes and the foot of the mountains of 

 Hodua and Bou-Kahil ; on the east it penetrates into the 

 JRegency of Tunis ; on the south it rises in a slight and 

 almost insensible slope towards the country of the Touareys ; 

 and on the west it stretches in a point along the Oued Mia as 



