Amid this tornado, an entire caravan, disorganized, broken, and overthrown, was disappearing beneath an avalanche of sand. The camels, flung pell-mell together, were uttering dull and pitiful groans; cries and howls of despair were heard issuing from that dusty and stifling cloud, and, from time to time, a parti-colored garment cut the chaos of the scene with its vivid hues, and the moaning and shrieking sounded over all, a terrible accompaniment to this spectacle of destruction.

Ere long the sand had accumulated in compact masses; and there, where so recently stretched a level plain as far as the eye could see, rose now a ridgy line of hillocks, still moving from beneath--the vast tomb of an entire caravan!

The doctor and Kennedy, pallid with emotion, sat transfixed by this fearful spectacle. They could no longer manage their balloon, which went whirling round and round in contending currents, and refused to obey the different dilations of the gas. Caught in these eddies of the atmosphere, it spun about with a rapidity that made their heads reel, while the car oscillated and swung to and fro violently at the same time. The instruments suspended under the awning clattered together as though they would be dashed to pieces; the pipes of the spiral bent to and fro, threatening to break at every instant; and the water-tanks jostled and jarred with tremendous din. Although but two feet apart, our aeronauts could not hear each other speak, but with firmly-clinched hands they clung convulsively to the cordage, and endeavored to steady themselves against the fury of the tempest.

Kennedy, with his hair blown wildly about his face, looked on without speaking; but the doctor had regained all his daring in the midst of this deadly peril, and not a sign of his emotion was betrayed in his countenance, even when, after a last violent twirl, the Victoria stopped suddenly in the midst of a most unlooked-for calm; the north wind had abruptly got the upper hand, and now drove her back with equal rapidity over the route she had traversed in the morning.

"Whither are we going now?" cried Kennedy.

"Let us leave that to Providence, my dear Dick; I was wrong in doubting it. It knows better than we, and here we are, returning to places that we had expected never to see again!"

The surface of the country, which had looked so flat and level when they were coming, now seemed tossed and uneven, like the ocean-billows after a storm; a long succession of hillocks, that had scarcely settled to their places yet, indented the desert; the wind blew furiously, and the balloon fairly flew through the atmosphere.

The direction taken by our aeronauts differed somewhat from that of the morning, and thus about nine o'clock, instead of finding themselves again near the borders of Lake Tchad, they saw the desert still stretching away before them.

Kennedy remarked the circumstance.

"It matters little," replied the doctor, "the important point is to return southward; we shall come across the towns of Bornou, Wouddie, or Kouka, and I should not hesitate to halt there."

"If you are satisfied, I am content," replied the Scot, "but Heaven grant that we may not be reduced to cross the desert, as those unfortunate Arabs had to do! What we saw was frightful!"

"It often happens, Dick; these trips across the desert are far more perilous than those across the ocean. The desert has all the dangers of the sea, including the risk of being swallowed up, and added thereto are unendurable fatigues and privations."

"I think the wind shows some symptoms of moderating; the sand-dust is less dense; the undulations of the surface are diminishing, and the sky is growing clearer."

"So much the better! We must now reconnoitre attentively with our glasses, and take care not to omit a single point."

"I will look out for that, doctor, and not a tree shall be seen without my informing you of it."

And, suiting the action to the word, Kennedy took his station, spy-glass in hand, at the forward part of the car.