Situation of Zones without Bain, and of Deserts. 365 



It is thus that, in the western portion, at Timbuctoo (lat. 

 17° 50' north), the rains, so abundant near the equatorial 

 zone, are already rare, and the soil is poor ; at El Araouan 

 (lat. 20° north), the rains are still less frequent, and hardly 

 any traces of verdure are visible ; soon afterwards, the desert 

 is reached, with its boundless horizon, its fiery sky, its rocks, 

 its sands, and the moveable parts of its surface in which the 

 winds hollow out valleys, raising, at the same time, pillars of 

 sand, whose fall is the only representation of showers. At 

 the northern limit of this immense land of desolation, there 

 appears, at first here and there, spaces covered with plants, 

 near El-Arib (lat. 28° north) ; these become more numerous 

 under the influence of some hyemal rains which are still but 

 little abundant in the steppes of Beled-el-Djerid (country of 

 dates), where, nevertheless, the ?vadis (valleys with temporary 

 torrents), and the vicinity of the Atlas, put an end to the 

 aridity. Here there is no longer a desert properly so called, 

 — for who would venture to give this name to a country 

 where one single tribe, that of the Arbaa, is 40,000 strong ! 

 In the time of the splendour of the caliphs, this Beled-el- 

 Djerid was of great importance, on account of its castles, its 

 fortresses, its towns, its gardens, its forests of palms, its com- 

 merce, and its activity. At the present day, Ain-Modhy has 

 been able to resist the power and perseverance of Abd-el-Ka- 

 der. All this necessarily presupposes a numerous population, 

 consequently also a favourable climate ; and hence it results 

 that the extension of our conquests in the south of Algeria is 

 constantly revealing to us productive districts ; for, up to 

 the present time, we have scarcely passed 35° N., which is 

 still very far removed from the region deserving the name of 

 desert. 



The coast of the Atlantic is not entirely free from the 

 nullity of rains of the middle system which we are defining; for 

 round Cape Barbas, from 22° to 21° N., two consecutive years 

 sometimes pass without the smallest trace of rain ; and the 

 same is the case in the Cape de Verd islands, which are some- 

 times deprived of rain for a period of even seven or eight 

 years. 



To the east, between the Nile and the Red Sea, there ex- 



