Bou-Djema had rejoined us.

“When the legs of the mohor tremble it is because the firmament is shaken,” he muttered.

“A storm?”

“Yes, a storm.”

“And you find that alarming?”

I did not answer immediately.  I was exchanging several brief words with Bou-Djema, who was occupied in soothing the camels which were giving signs of being restive.

Morhange repeated his question.  I shrugged my shoulders.

“Alarming?  I don’t know.  I have never seen a storm on the Hoggar.  But I distrust it.  And the signs are that this is going to be a big one.  See there already.”

A slight dust had risen before the cliff.  In the still air a few grains of sand had begun to whirl round and round, with a speed which increased to dizziness, giving us in advance the spectacle in miniature of what would soon be breaking upon us.

With harsh cries a flock of wild geese appeared, flying low.  They came out of the west.

“They are fleeing towards the Sebkha d’Amanghor,” said Bou-Djema.

There could be no greater mistake, I thought.

Morhange looked at me curiously.

“What must we do?” he asked.

“Mount our camels immediately, before they are completely demoralized, and hurry to find shelter in some high places.  Take account of our situation.  It is easy to follow the bed of a stream.  But within a quarter of an hour perhaps the storm will have burst.  Within a half hour a perfect torrent will be rushing here.  On this soil, which is almost impermeable, rain will roll like a pail of water thrown on a bituminous pavement.  No depth, all height.  Look at this.”

And I showed him, a dozen meters high, long hollow gouges, marks of former erosions on the rocky wall.

“In an hour the waters will reach that height.  Those are the marks of the last inundation.  Let us get started.  There is not an instant to lose.”

“All right,” Morhange replied tranquilly.

We had the greatest difficulty to make the camels kneel.  When we had thrown ourselves into the saddle they started off at a pace which their terror rendered more and more disorderly.

Of a sudden the wind began, a formidable wind, and, almost at the same time the light was eclipsed in the ravine.  Above our heads the sky had become, in the flash of an eye, darker than the walls of the canyon which we were descending at a breathless pace.

“A path, a stairway in the wall,” I screamed against the wind to my companions.  “If we don’t find one in a minute we are lost.”

They did not hear me, but, turning in my saddle, I saw that they had lost no distance, Morhange following me, and Bou-Djema in the rear driving the two baggage camels masterfully before him.

A blinding streak of lightning rent the obscurity.  A peal of thunder, re-echoed to infinity by the rocky wall, rang out, and immediately great tepid drops began to fall.  In an instant, our burnouses, which had been blown out behind by the speed with which we were traveling, were stuck tight to our streaming bodies.