Edinburgh and Moscow are in precisely the same latitudes, yet the one
is equable in temperature while the other endures the rigours of an
arctic winter. The South of Iceland also suffers less from cold than
do the great central plains of Europe. And why? Simply because their
different climates are the result of special conditions or influences
of Nature, and what the Gulf Stream does for the British Isles the
deserts of Africa effect not only for Egypt, but for the whole of
Southern Europe, whose genial climate is mainly caused by the warm air
generated on these sun-baked barren lands.

Now let us see what the desert is like in appearance. It is a very
common impression that the desert is simply a flat expanse of sand,
colourless and unbroken; in reality it is quite different, being full
of variations, which give it much the same diversity of interest as
the ocean.

The colour of the sand varies infinitely, according to its situation.
Thus the desert which surrounds Assuan, which is composed of decimated
granite and Nile silt, is generally grey; in Nubia the sand is formed
of powdered sandstone of a curiously golden tint, while the desert of
Suez, which abuts on Cairo and the Delta provinces, is generally white
in tone, due to the admixture of limestone dust of which it is largely
composed. The great Sahara also is no monotonous stretch of sand, but
is to a great extent covered by wild herbs of many kinds, which often
entirely screen the sand from view, and give it the appearance of a
prairie.

Nor is the desert always flat, for its huge undulations suggest ocean
billows petrified into stillness, while rocky hills and
earthquake-riven valleys give it a fantastic variety which is wildly