554 SANDS OF EGYPT. 
siderable is the quantity yet remaining on the borders of 
Egypt, that a wall four or five feet high suffices for centuries 
to check its encroachments. This is obvious to the eye of 
every observer who prefers the true to the marvellous; but 
the old-world fable of the overwhelming of caravans by the 
fearful simoom—which even the Arabs no longer repeat, if 
indeed they are the authors of it—is so thoroughly rooted in 
the imagination of Christendom that most desert travellers, of 
the tourist class, think they shall disappoint the readers of 
their journals if they do not recount the particulars of their 
escape from being buried alive by a sand-storm, and the 
popular demand for a “sensation” must be gratified accord- 
ingly. * 
Another circumstance is necessary to be considered in esti- 
mating the danger to which the arable lands of Egypt are 
exposed. The prevailing wind in the valley of the Nile and 
its borders is from the north, and it may be said without 
exaggeration that the north wind blows for three-quarters of 
the year.t The effect of winds blowing up the valley is to 
drive the sands of the desert plateau which border it, in a 
direction parallel with the axis of the valley, not transversely 
to it; and if it ran in a straight line, the north wind would 
* Wilkinson says that, in much experience in the most sandy parts of the 
Libyan desert, and much inquiry of the best native sources, he never saw 
or heard of any instance of danger to man or beast from the mere accumu- 
lation of sand transported by the wind. Chesney’s observations in Arabia, 
and the testimony of the Bedouins he consulted, are to the same purpose. 
The dangers of the simoom are of a different character, though they are 
certainly aggravated by the blinding effects of the light particles of dust 
and sand borne along by it, and by that of the inhalation of them upon the 
respiration. 
+ In the narrow valley of the Nile, bounded as it is, above the Delta, by 
high cliffs, all air-currents from the northern quarter become north winds, 
though of course varying in partial direction, in conformity with the sinu- 
osities of the valley. Upon the desert plateau they incline westwards, 
and have already borne into the valley the sands of the eastern banks, 
and driven those of the western quite out of the Egyptian portion of the 
Nile basin. 
