298 PHYSICAL HISTORY OF MAN. 



The fertile portion of Africa, is surrounded by water on every side 

 except the north; where a vast uninhabitable space, seems impassa- 

 ble to man in his ruder state. 



There exists, however, a natural highway across the Sahara, in 

 the unique geographical position of the Nile : and individuals, by 

 following the banks, or floating on the bosom of this remarkable 

 river, could easily reach the countries of the North. 



The acquisition of domestic animals, and more particularly that 

 of the camel, wrought a change throughout the region in question. 

 And one of the camel routes, may be here specified, as connecting 

 countries which make a conspicuous figure in History. Com- 

 mencing in the table-land of Abyssinia, and crossing the entrance 

 of the Red Sea, the route leads northward, and through the narrow- 

 est part of Arabia, to Persia (a country more conveniently accessible 

 from the heart of Africa than may at first be supposed); continuing 

 eastward, the route terminates in Hindoostan, at the second grand 

 natural barrier of races and nations, the Himalaya range of moun- 

 tains. 



In order to a clear understanding of the history of Oriental nations, 

 it is necessary to observe : That the above Desert tract, contains four 

 principal oases : the first, consists of Egypt, or of the alluvial flats of 

 the Nile ; the second, consists of the alluvial flats of the Euphrates ; 

 the third, of a strip of land along the southern margin of the Caspian; 

 and the fourth, of the alluvial flats of the Indus. 



The difference in the circumstances between intercourse by land and 

 by sea, involves a corresponding difference in the state of the diflfusion 

 of knowledge. But successive waves of social revolution, are traceable 

 in the relics of ancient nations preserved in Hindoostan : likewise, in 

 the slow progress of innovation in mountain fastnesses, and in other 

 secluded situations. Thus, the people of the western Sahara, con- 

 tinue to entertain the belief: That Cimmerian darkness overhangs the 

 Atlantic, and that the sun rises only for themselves. They have been 

 known to ask visiters, "Do you sow" barley in your houses?" mean- 

 ing the ships, in which they supposed that Europeans were born and 

 passed their lives. 



