Atlas Mountains.
Where there are no Atlas Mountains, it begins almost at the
Mediterranean's edge. In the valleys of the Atlas and along the
Mediterranean coast there is a strip of fertile land, wide here, narrow
there, that produces grain and fruit. The Arabs call it the
_Tell_. "Beyond the Tell is Sah-ra," or the Sahara. This is the name
which the Arabs apply to the archipelago of fertile spots, or oases.
Beyond the zone of oases is the desert. One becomes instantly and
painfully aware that it is a desert on leaving the last oasis. Go a
thousand miles southward, eastward, or westward from Tripoli, and one
encounters but a single thing--an ocean of orange-colored rock waste,
the Guebla of the Arabs.

[Illustration: On the sands of the desert]

The desert is a desert for want of water only. There is no lack of
nutrition in the soil, nor is there anything in surface or temperature
that makes a desert unproductive. Temperature and winds reach great
extremes in fierceness, however. The temperature of the air in the
noonday sun will often exceed one hundred and forty-five degrees; it may
reach one hundred and fifty-five degrees. In the shade it frequently
climbs to one hundred and thirty degrees in the vicinity of the tropics.
Unless one is at a considerable altitude there is not much relief at
night, though the thermometer may drop to ninety degrees. Farther north,
however, and at an altitude of five thousand feet or more, the
temperature of the night is even more cruel than that of the day.
Immediately after sunset a sharp chill becomes perceptible. At first it
is a welcome relief from the intolerable heat. By nine o'clock it begins
to cut like a stiletto, and at midnight the water suspended in shallow
dishes clinks into ice. The drivers burrow deep into the sand and wrap
woollen baracans about them; the camels shiver and even blubber like
whipped bullies.

The air is so dry, however, that the extreme heat of day is by no means
insupportable. Sunstroke is almost unknown, and even the tragedy of
perishing for want of water is very rare; for the caravan drivers know
just where to find water, and there are many hidden watering places that
are known to the crafty Tuaregs and Bedouins. Many of the watering
places are wells that have been sunk in various localities along the
caravan trails. The intense heat, great depth of rock waste, and dry air
are not favorable to the above-ground flow of rivers. But nearly every
river h