CENTRAL AND SOUTHERN AFRICA. 149' 



desert since the historic period [seit dem Alterthiime die Wiistenbildung, 

 ohne Unterbrechimg im Fortschreiten begriffen ist]." 



Farther on, Chavanne remarks as follows : " That, however, the quantity 

 of water [der Wasserschatz] in the Sahara has diminished, and that this 

 region has become drier since the days of historical antiquity, can now be 

 no lon2;er doubted." * 



The evidence of a great climatic change in Northern Africa, and generally 

 in the countries bordering the Mediterranean, is so clear, that it is not neces- 

 sary to dwell longer upon this region. As to the central and southern por- 

 tions of that continent, it is not to be expected that such an array of facts 

 as has been presented with regard to Egypt and the Sahara could be brought 

 forward, even if desiccation had proceeded all over Africa with the same 

 rapidity as on its northern borders. In the first place, the central portion 

 of that continent is quite differently situated from the northern area with 

 reference to those meteorological conditions influencing precipitation, so 

 that the larger part of it is superabundantly supplied with moisture, at 

 least during a certain season of the year. And a diminution of an abundant 

 supply to one less abundant, but still ample for the wants of animal and 

 vegetable life, is not, by any means, a phenomenon of the same character 

 as that of a falling-ofF from moderate to very small, although, in reality, 

 the actual decrease ma}^ be as great in one case as in the other. It is only 

 when the decrease of precipitation has reached that point Avhere its effects 

 begin to be marked in making life difficult, that much heed would be likely 

 to be paid to it. 



But, again. Central Africa is a region which is inhabited by uncivilized 

 races, and of which the scientific exploration has but just begun, the prin- 

 cipal geographical facts concerning it being, as yet, hardly made out in 

 outline. Moreover, it has no recorded history, other than that offered 

 by nature herself; while data furnished by trained geological observers are 

 entirely wanting, at least for much the larger portion of the country. The 

 existence of numerous lakes, many of which are of great size, so that the 

 whole region is one of the most remarkable, in respect to the importance 

 of its lacustrine areas, of any on the globe, is, however, now a well-ascer- 

 tained fact, and evidence that these lakes have been diminishing in size during 

 recent times is by no means wanting. Indeed, that most remarkable trav- 

 eller, Livingstone, seems, at an early period of his investigations in Africa, 



• 1. c, p. 627. 



