458 
SANDS OF EGYPT. 
speak more precisely, roll the finer beach sand to considerable 
distances into the interior. But this is a very slow process, and 
the exaggerations of travellers have diffused a vast deal of 
popular error on the subject. 
Sands of Egypt. 
In the narrow valley of the Nile—which, above its bifur¬ 
cation near Cairo, is, throughout Egypt and Nubia, generally 
bounded by precipitous cliffs—wherever a ravine or other con¬ 
siderable depression occurs in the wall of rock, one sees what 
seems a stream of desert sand pouring down, and common 
observers have hence concluded that the whole valley is in 
danger of being buried under a stratum of infertile soil. The 
ancient Egyptians apprehended this, and erected walls, often 
of unburnt brick, across the outlet of gorges and lateral val¬ 
leys, to check the flow of the sand streams. In later ages, 
these walls have mostly fallen into decay, and no preventive 
measures against such encroachments are now resorted to. But 
the extent of the mischief to the soil of Egypt, and the future 
danger from this source, have been much overrated. The sand 
on the borders of the Nile is neither elevated so high by the 
wind, nor transported by that agency in so great masses, as is 
popularly supposed; and of that which is actually lifted or 
rolled and finally deposited by air currents, a considerable 
proportion is either calcareous, and, therefore, readily decom¬ 
posable, or in the state of a very fine dust, and so, in neither 
case, injurious to the soil. There are, indeed, both in Africa and 
in Arabia, considerable tracts of fine silicious sand, which may 
be carried far by high winds, but these are exceptional cases, 
and in general the progress of the desert sand is by a rolling 
motion along the surface.* So little is it lifted, and so incon- 
* Sand heaps, three and even six hundred feet high, are indeed formed 
by the wind, but this is effected by driving the particles up an inclined 
plane, not by lifting them. Bremontier, speaking of the sand hills on the 
western coast of France, says: “The particles of sand composing them 
are not large enough to resist wind of a certain force, nor small enough to 
