gain proceed southward."

And he began to shout that they should resume their seats on the camels.

But at this moment something happened which entirely changed the
situation.

Suddenly, the dusky, almost black, clouds of sand were illumined with a
livid light. The darkness then became still deeper, but at the same
time there arose, slumbering on high and awakened by the whirlwind,
thunder; it began to roll between the Arabian and Libyan
deserts,--powerful, threatening, one might say, angry. It seemed as if
from the heavens, mountains and rocks were tumbling down. The deafening
peal intensified, grew, shook the world, began to roam all over the
whole horizon; in places it burst with a force as terrible as if the
shattered vault of heaven had fallen upon earth and afterwards it again
rolled with a hollow, continual rumble; again it burst forth, again
broke, it blinded with lightning, and struck with thunderbolts,
descended, rose, and pealed continuously.* [* The author heard in the
vicinity of Aden thunder which lasted without intermission for half an
hour. See "Letters from Africa."]

The wind subsided as if overawed, and when after a long time somewhere
in the immeasurable distance the chain-bolt of heaven rattled, a deadly
stillness followed the thunder.

But after a while in that silence the voice of the guide resounded.
"God is above the whirlwind and the storm. We are saved."

They started. But they were enveloped by a night so impenetrable that
though the camels ran close together, the men could not see each other
and had to shout aloud every little while in order not to lose one
another. From time to time glaring lightning, livid or red, illuminated
the sandy expanse, but afterwards fell a darkness so thick as to be
almost palpable. Notwithstanding the hope, which the voice of the guide
poured into the hearts of the Sudanese, uneasiness did not yet leave
them, because they moved blindly, not knowing in truth in which
direction they were going;--whether they were moving around in a circle
or were returning northward. The animals stumbled against each other
every little while and could not run swiftly, and besides they panted
strangely, and so loudly that it seemed to the riders that the whole
desert panted from fear. Finally fell the first drops of rain, which
almost always follows a hurricane, and at the same time the voice of
the guide broke out amidst the darkness:

"Khor!"

They were above a ravin