188 
DESCRIPTIONS OF EGYPT. 
islands are generally surrounded, suggests the ob- 
vious manner of their formation. The copious 
dew which condenses on the tops of these moun- 
tains, after filtering through the rocks, emerges in 
springs amid the valleys beneath, and produces a 
luxuriant vegetation, The Egyptian Oases, which 
are two in number, consist of a long range of iso- 
lated spots of verdur(3, in the low and sandy de- 
sert which lies beyond that western range of 
mountains, and runs parallel to the course of the 
Nile. These fertile tracts are separated by sandy 
plains of various extent. The distance between 
the nearest extremities of the two Oases is about 
forty miles, an interval greater than that which 
separates any of the other islands, and which, as 
Rennell conjectures, has caused the division of 
them into two great clusters, denominated the 
Greater and Lesser Oases. The Greater Oasis, 
commonly termed El Wah, is by Leo named Eioa- 
cath or Eloacheth, while the Lesser, termed El 
Wal-el Gerbe, receives from that author the ap- 
pellation of Gerbe.t The Arabian Jacuti, includ- 
ing Siwah or Ammonia, enumerates three Oases, 
which he arranges in three distinct lines, separat- 
ed by ridges of mountains parallel to the course 
of the Nile, like the continents of the earth in 
* Rennell's Geography of Herodotus, p. 564. 
t Leo Africanus, p. 10. 
