]G4 THE DESICCATION OF AFRICA. 



somewhat irregularly, east and west. These places were 

 ■ connected at one time with the present Nile by the Bahr- 

 bila-ma, but if the western Nile did flow on the desert side 

 of the plateau escarpment, as there is reason to believe it 

 did, then, at an earlier stage it must have penetrated here 

 also. There are a number of salt-marshes, or sebkhas, 

 between Siwa and Jarabub, that are fed by underground 

 water; they form a series of depressions connecting Jarabub 

 with Augila. Rolfs conceived the project of transforming 

 this chain of oases into an inland gulf by admitting the 

 Mediterranean waters through a cutting to the Wady Fareg 

 or the Bir Rassam. A waterway, he thought, might thus be 

 opened far into the arid Libyan Desert, the climate improved 

 and Cyrenaica converted into an island in the middle of the 

 Mediterranean- Rolfs himself, however, gave up the idea 

 after his expedition into the Libyan Desert, when it was 

 found that Siwa alone with its eastern extensions fell below 

 the level of the Mediterranean (Siwa -98, Sittra -80, and 

 the Birket-el-Ourun - 141 feet). Augila and Jalo were, on 

 the contrary, found to stand 130 and 296 feet respectively 

 above sea-level, so that the marine inlet cannot have pene- 

 trated very far in recent geological times. Rudaire had a 

 similar project in connection with the shotts of Algeria. 

 Beyond these marginal floodings, no engineering feat can 

 bring the Mediterranean into the Sahara, because it stands 

 much above sea-level. In 1877 Donald Makenzie proposed a 

 plan for opening Central Africa by flooding the Sahara; he 

 published a book, "The Flooding of the Sahara," which was 

 widely read, and is the reason that the idea is so prevalent. 

 There are no facts to support Makenzie. 



As bearing on the question of the Proto-Congo, we find 

 a very large western tributary of the Nile coming from the 

 volcanic region of Darfur ; this is the Wady Malik, that joins 

 the Nile at Old Dongola. Nowadays the Marra Hills have no 

 moisture to spare for the plains and the fact that a very large 

 river once took its rise in these hills, shows that the climatic 

 conditions were very much more favourable at one time. 

 According to our arguments, the Marra Hills lay in the bend 

 of. the Proto-Congo and its once copious rainfall is readily 

 explained by this fact. 



In the Sudan, the Nile has a swampy region, like Lake 

 Chad, called the Bahr-el-Ghazal. There is a more or less well- 

 defined river-bed which bears this name, but it has practically 

 no fall. On the east, the Sobat enters the Bahr-el-Ghazal on 

 the same course, but flowing in the opposite direction, and 

 if both rivers are in flood at the same time there is a great 

 congestion of water at the confluence. It is an axiom that 

 when a river system contains such a region of dead water, 



