21. Desert Sands - Page 2

those parts of the world where the
run of mountain ranges, prevalent winds, and ocean currents conspire to
render the average rainfall as small as possible. But, strangely enough,
there is a large irregular belt of the great eastern continent where
these peculiar conditions occur in an almost unbroken line for thousands
of miles together, from the west coast of Africa to the borders of
China: and it is in this belt that all the best known deserts of the
world are actually situated. In one place it is the Atlas and the Kong
mountains (now don't pretend, as David Copperfield's aunt would have
said, you don't know the Kong mountains); at another place it is the
Arabian coast range, Lebanon, and the Beluchi hills; at a third, it is
the Himalayas and the Chinese heights that intercept and precipitate all
the moisture from the clouds. But, from whatever variety of local causes
it may arise, the fact still remains the same, that all the great
deserts run in this long, almost unbroken series, beginning with the
greater and the smaller Sahara, continuing in the Libyan and Egyptian
desert, spreading on through the larger part of Arabia, reappearing to
the north as the Syrian desert, and to the east as the desert of
Rajputana (the Great Indian Desert of the Anglo-Indian mind), while
further east again the long line terminates in the desert of Gobi on the
Chinese frontier.

In other parts of the world, deserts are less frequent. The peculiar
combination of circumstances which goes to produce them does not
elsewhere occur over any vast area, on so large a scale. Still, there is
one region in western America where the necessary conditions are found
to perfection. The high snow-clad peaks of the Rocky Mountains on the
one side check and condense all the moisture that comes from the
Atlantic; the Sierra Nevada and the Wahsatch range on the other, running
parallel with them to the west, check and condense all the moisture that
comes from the Pacific coast. In between these two great lines lies the
dry and almost rainless district known to the ambitious western mind as
the Great American Desert, enclosing in its midst that slowly
evaporating inland sea, the Great Salt Lake, a last relic of some
extinct chain of mighty waters once comparable to Superior, Erie, and
Ontario. In Mexico, again, where the twin ranges draw closer together,
desert conditions once more supervene. But it is in central Australia
that the causes which lead to the desert state are, perhaps on the
whole, best exemplified. There, ranges of high mountains extend almost
all round the coasts, and so completely intercept the rainfall which
ought to fertilise the great central plain that the rivers are almost
all short and local, and one thirsty waste spreads