STEPPES AND DESERTS. 3 



between Wadi Nun and the White Cape, the moist sea-air 

 rushes in to fill the vacuum caused by these vertically ascend- 

 ing currents of air. The, navigator, in steering towards the 

 mouth of the river Gambia, through a sea thickly carpeted 

 with weeds, infers by the sudden cessation of the tropical east 

 wind (7), that he is near the far-spreading and radiating sandy 

 desert. 



Flocks of swift-looted ostriches and herds of gazelle* 

 wander over this boundless space. With the exception of 

 the newly discovered group of Oases, rich in springs, whose 

 verdant banks are frequented by nomadic tribes of Tibbos 

 and Tuaricks (8), the whole of the African deserts may be 

 regarded as uninhabitable by man. It is only periodically 

 that the neighbouring civilized nations venture to traverse 

 them. On tracks whose undeviating course was determined 

 by commercial intercourse thousands of years ago, the long 

 line of caravans passes from Tafilet to Timbuctoo. or from 

 Mourzouk to Bornou ; daring enterprises, the practicability of 

 which depends on the existence of the camel, the ship of the 

 desert (9), as it is termed in the ancient legends of the East. 



These African plains cover an area which exceeds almost 

 three times that of the neighbouring Mediterranean. They 

 are situated partly within and partly near the tropics, a 

 position on which depends their individual natural character. 

 On the other hand, in the eastern portion of the old continent 

 the same geognostic phenomenon is peculiar to the temperate 

 zone. 



On the mountainous range of Central Asia, between the 

 Gold or Altai Mountain and the Kouen-lien (10), from the 

 Chinese wall to the further side of the Celestial Mountains, 

 and towards the Sea of Aral, over a space of several thousand 

 miles, extend, if not the highest, certainly the largest Steppes 

 in the world. I myself enjoyed an opportunity, full thirty 

 years after my South American travels, of risiting that por- 

 tion of the Steppes which is occupied by Kalmuck -Kirghiz 



B'2 



