SAND-DUNES AND BLOWING SAND. 
139 
But however this may be, it is certain that until within the 
last sixty years, and for centuries before that, the Landes have 
been nothing but waste blowing sand, a terror to the cultivators 
of the fertile soil on their eastern side. When the Moors were 
finally driven from Spain, they asked permission to live in this 
desert, which they would reclaim : this request was refused. 
Possibly we may form some idea of the material loss which 
France inflicted on herself in thus rejecting what Spain had 
not the wisdom to keep ; but no one can estimate the intel- 
lectual loss which Europe has sustained in the forced extinction 
of Arabian science. 
There is much sand along the south-west and south shores of 
the Mediterranean Sea. The dunes only fringe the seaward 
face of the plains of Sharon and Philistria, spreading over a 
somewhat wider space near Joppa ; but they become of much 
greater importance farther south, and they form a broad zone 
of hills, sometimes ten miles wide, along the northern margin of 
the delta of the Nile. Much of the coast of Barbary is bordered 
by sand-hills ; in some places these are backed by fertile plains, 
but elsewhere they blend with that vast inland sea of sand, the 
great Sahara. 
An enormous arid area extends from the West Coast of Africa, 
across the Sahara, the Libyan Desert, the Peninsula of Sinai, 
the Syrian Desert, the valleys of the Euphrates and Tigris, 
through Persia, and far into Central Asia. Throughout this 
vast expanse of country there is an exceedingly small rainfall, 
so small that in some physical maps it is coloured as a “ rain- 
less district,” and such in some parts it probably is. There is 
necessarily little or no vegetation to cover the rock and preserve 
the soil. There is a large proportion of sandstone strata 
(of different geological ages) along this line, which, yielding 
to the powerful influence of a tropical heat,* and to atmo- 
spherical agencies, produce a large quantity of loose sand. If 
there were sufficient rainfall to feed permanent streams, the 
debris of the rocks would be gradually carried away; but this 
not being the case, the sand remains, and becomes the sport of 
every gust of wind. 
There can be little doubt that this is the origin of much of 
the sand of the desert ; not, perhaps, of all. There is 
abundant evidence that the Sahara has been covered by the sea 
at quite a recent geological date, and large quantities of the 
sand which covers it may date from that period. Some, too, 
has been derived from the present sea-bed ; first as coast-dunes, 
-afterwards being drifted inland. 
* Although from 15° to 30° north of the equator, Nubia, with the desert 
to the west, and Central Arabia, form the hottest district in the world. 
