upon us. It is useless to look for shelter, for the dunes are too flat
to protect us from the wind. And now the storm sweeps down, and it
becomes suffocatingly close and hot. The dromedaries seem uneasy, halt,
and turn away from the wind. We dismount. The dromedaries lie down and
bury their muzzles in the sand. We wrap up our heads in cloths and lie
on our faces beside our animals to get some shelter between them and the
ground. And so we may lie by the hour panting for breath, and we may be
glad if we get off with our lives from a _samum_ when we are out in the
desert. Even in the oases it causes a feeling of anxiety and trouble,
for the burning heat is most harmful to palms and crops. The temperature
may rise to 120 deg. in this dangerous storm, which justifies its name of
"poison wind."

The storm passes off, the air becomes clear and is quiet and calm, and
the sun has again its golden yellow brilliance. It is warm, but not
suffocating as it was. The heated air vibrates above the sand. Beside
our road appears a row of palms and before them a silver streak of
water. The guide, however, goes on in quite a different direction, and
when we ask him why, he answers that what we see is a mirage, and that
there is no oasis for many days' journey in the direction in which we
see the palms.

In the evening we come to a real oasis, and there we are glad to rest a
couple of days. Here are a hundred wells, here the ground is cultivated
in the shade of the palms, here we can enjoy to the full the moist
coolness above the swards of juicy grass. The oasis is like an island in
the desert sea, and between the palm trunks is seen the yellow level
horizon, the dry, heated desert with its boundless sun-bathed wastes.

If we now turn off towards the north-west, Fezzan is the next country
which our route touches. It is a paradise of date palms. They occur in
such profusion that even dromedaries, horses, and dogs are fed with the
fruits. The surface of the ground also has undergone a great change, and
is not so sterile and choked with sand as in the Libyan desert. Here and
farther to the west the country becomes more hilly. Ridges and bosses of
granite and sandstone, weathered and scorched by the sun, stand up here
and there. Extensive plateaus covered with gravel are called _hammada_;
they are ruins of former mountains which have burst asunder. In the
Sahara the differences of temperature between day and night are very
great. The dark,