246 GRAPHIC DESCRIPTION OF AFRICA. 



noxious serpents which were so numerous in that country; others 

 that there was supposed to be some analogy between the plumage of 

 the bird and one of the phases of the moon; while a third opinion 

 is that the birds were regarded with favor, because, their annual 

 migration into Egypt taking place at the period of the rising of the 

 Nile, they were considered as the harbingers of that event. 



A glowing description of tropical scenery finds a striking con- 

 trast of the account given of the African desert, and the perils 

 which often overtake travelers who attempt to cross it. 



TERRIFIC SAND STORMS. 



The plain of Sahara is the great typical desert. Its name comes 

 from an Arabic word, which means the plain. Not that the great 

 desert is by any means an unbroken plain, or destitute of great 

 variety in its physical characteristics. The true sandy desert occu- 

 pies but a relatively small portion of the space marked upon our 

 maps as the desert of Sahara; and even upon the surface of this 

 "true" desert the distribution of sand is very unequal. The stratum 

 of the sand in some parts is so thin that the underlying limestone is 

 visible through it. The sandy region attains its greatest extent in 

 the Libyan desert, and masses of sand still drift in from the Medi- 

 terranean, to settle down upon a bed which in a recent period was 

 buried beneath the waves of the sea. These sand floods extend 

 westward to Tripoli. Near that town the sandy stretches are varied 

 by plantations of palm trees and fields of corn; true deserts of 

 yellow sand, passing like a yellow ribbon from west to ea^t, between 

 fields of wheat and barley. 



The western Mongolian desert contains plains of sand perfectly 

 corresponding with those of the Sahara and the Arabian desert. 

 Mounds of loose sand are blown together and scattered again by 

 the wind: a mere breeze is enough to wipe out all trace of a long 

 caravan crossing the waste. The sand is so extremely fine and 

 light, that in sudden storms of wind trenches of thirty or forty 

 feet deep are hollowed out, and swelling w^aves are raised like those 

 of the Libyan desert, making the journey tedious and difficult to 

 the camels as they cross the shifting plain. 



