138 DUST STORMS. 



storm." They are very common in all dry countries, 

 and consist of a minor kind of tornado, unaccom- 

 panied by rain, which sweeps before it tremendous 

 clouds of dust and sand; in the most violent of these 

 storms the dust cloud becomes mixed with gravel, 

 which beats against the face, almost like a charge of 

 small shot. Such storms sometimes come up so sud- 

 denly, and with such extreme violence, that it is diffi- 

 cult to face the driving clouds of sand, etc. We were 

 once caught in a tremendous whirlwind of sand and 

 dust of this kind, on the road near Damascus, in Syria. 

 The horses were obliged to be frequently halted, and 

 turned with their backs to the wind, and it was only 

 during the lulls in the storm that travelling became 

 possible. South Africa is notorious for this sort of 

 storms, and in our chapter on the Desert Zone we 

 shall relate some curious facts concerning them. 



The w r altzing columns of sand, which are so fre- 

 quently seen in the Nubian and other deserts, caused 

 by whirlwinds, or eddies of heated air, are among 

 the most curious of these phenomena, and may fre- 

 quently be seen from the decks of Nile boats proceed- 

 ing up the river, beyond the first cataract, and 

 occasionally they sweep across the river itself, and so 

 obstruct the view that steering becomes difficult, or 

 even impossible. These dust columns, though perhaps 

 they may not attain the same magnitude in Lo\ver 

 Egypt as they do in the Nubian desert (where the 

 late Sir Samuel Baker has estimated some that he 

 saw between Korosko and Abu Hammed, as from 

 1000 to 1500 feet in height), are still frequently seen 

 there rising to a great altitude. On the Karroos in 

 South Africa, we have also been assured by 



