I 



THE DESEUTS OF AFRICA AND ASIA. 367 



tlaeir long domination of Spain, so that had this interesting colony not 

 been artificially maintained, there would be now-a-days not a single 

 monkey on this rock ; the fact is, that in 1856 they had almost entirely 

 disappeared, when Sir William Codrington caused a new importation to 

 be made from northern Africa. Just as the cedar, the monkeys of 

 Gibraltar (the Macacus inuus of Algeria) would be found now as 

 indigenous inhabitants on many shores of Greece, Italy, Spain, &c., 

 had they existed before the separation of Europe from Africa. An 

 additional proof of the recent immigration of the monkey in Africa is-, 

 that the quaternary fauna of the caves of Gibraltar, so carefully studied 

 by English geologists (Busk, Smith, Leith Adams, &c.), has not yielded 

 any remains of quadrumana ; and A. R. Wallace admits' that, evea 

 at the Miocene epoch, monkeys as well as the large mammals now 

 characteristic of Africa (lion, elephant, hycena, rhinoceros, hippopotamus, 

 &c.) were spread over Central Europe, but still did not inhabit Africa, 

 into which they migrated at a comparatively recent time. 



I will here conclude my very rapid physical sketch of the Sahara- 

 Lybian desert by a summary of the most prominent features of the 

 geological history of that country ; but before doing it, I wish to say a 

 few words about the important scheme of the creation of an inland sea in 

 the Sahara, which has been proposed to the French Government by 

 Commander Roudaire. As I have fully discussed the question in my last 

 work upon Algeria,^ I will content myself only with the following 

 remarks. 



The project of this distinguished engineer consists of introducing the 

 water of the Gulf of Gabes into the interior of Tunisia and Algeria, by 

 cutting through the isthmus which separates the gulf from the large 

 lake El-Fedjedj (Tritonis lacus of the ancients), situated under the 

 sea-level, as are a whole series of lakes (Chotts) extending in a direct lin& 

 from east to west, from the El-Fedjedj far into the interior of Algeria. 

 Now, Commander Roudaire thinks that the consequence of cutting the- 

 Isthmus of Gabes, the breadth of which is about 18 miles, would be to 

 spread the sea-water over a space of about 380 miles (320 kilometres) 

 of length from east to west, and about 70 to 80 miles (50 to 60 kilo- 

 metres) of breadth. The chief result of such a work would be, according 

 to Commander Roudaire, a great improvement in the climate of this- 

 part of Sahara, because this large water-surface would give rise to an 

 enormous evaporation, which, transported by the south, south-east, or 

 south-west winds, into the northern regions of Algeria and Tunisia, must- 

 needs become condensed in passing over the Aures Mountains, and be- 

 dissolved in copious rains. Moreover, Commander Roudaire declares that 

 the creation of this large gulf or inland sea would be nothing else than 

 the re-establishment of what has previously existed ; for, supported by 

 the authority of Ptolemy and other ancient geographers, he believes thai 

 formerly the Isthmus of Gabes did not separate the sea from the lake of 

 Tritonis (El-Fedjedj), and that, consequently, the sea penetrated very far 

 into the interior of the Sahara. 



At all events, the chief point on which the success of the whole enter- 

 prise depends is the question, whether the prevailing winds in this part of 



' Quart. Journ. of tJw Gcol. Soc. 1878, vol. xxxiv. p. ,34. 



* Loc. cit. pp. 539-551. M. Cosson has just published upon that subject an 

 important work entitled : Sur le Projet de creation en Algerie et en TStniiie d'une mer 

 intcrieure. 



