116 STEPPES AND DESERTS. 



comme celui de la mer se deroulait devant nous/' Between 

 Biscara and Sidi Ocba the ground is only 228 (243 Eng.) 

 feet above the level of the sea. The inclination increases 

 considerably towards the south. In another work, (Asie 

 Centrale, T. ii. p. 320), where I have brought together 

 everything relating to the depression of some portions of 

 continents below the level of the sea, I have already noticed 

 that according to Le Pere the "bitter lakes" on the 

 isthmus of Suez, when they have a little water, and, 

 according to General Andreossy, the Natron lakes of 

 Eayoum, are also lower than the level of the Mediter- 

 ranean. 



Among other manuscript notices of M. Fournel, I 

 possess a vertical geological profile, which gives all the 

 inflexions and inclinations of the strata, representing a 

 section of the surface the whole way from Philippeville on 

 the coast to the Desert of Sahara, at a spot not far from 

 the Oasis of Biscara. The direction of the line on which 

 the barometric measurements were taken is south 20 west; 

 but the elevations determined are projected, as in my Mexican 

 profiles, on a different plane, a north-south one. Ascend- 

 ing uninterruptedly from Constantine, at an elevation of 

 332 toises (2122 Eng. feet), the culminating point is found 

 between Batnah and Tizur, at an elevation of only 560 

 oises (3580 Eng. feet). In the part of the desert situated 

 between Biscara and Tuggurt, Fournel has had a series of 

 Artesian wells dug with success (Comptes Eendus de TAcad. 

 des Sciences, t. xx. 1845, p. 170, 882, and 1305). We 

 learn from the old accounts of Shaw, that the inhabitants of 

 the country knew of a subterranean supply of water, and 



