The horses were spurred on to the utmost, and Thaouka led the way, bounding over the water as if it had been his natural element. Certainly he might justly have been called a sea-horse-- better than many of the amphibious animals who bear that name.

All of a sudden, about ten in the morning, Thaouka betrayed symptoms of violent agitation. He kept turning round toward the south, neighing continually, and snorting with wide open nostrils. He reared violently, and Thalcave had some difficulty in keeping his seat. The foam from his mouth was tinged with blood from the action of the bit, pulled tightly by his master's strong hand, and yet the fiery animal would not be still. Had he been free, his master knew he would have fled away to the north as fast as his legs would have carried him.

"What is the matter with Thaouka?" asked Paganel. "Is he bitten by the leeches? They are very voracious in the Argentine streams."

"No," replied the Indian.

"Is he frightened at something, then?"

"Yes, he scents danger."

"What danger?"

"I don't know."

But, though no danger was apparent to the eye, the ear could catch the sound of a murmuring noise beyond the limits of the horizon, like the coming in of the tide. Soon a confused sound was heard of bellowing and neighing and bleating, and about a mile to the south immense flocks appeared, rushing and tumbling over each other in the greatest disorder, as they hurried pell-mell along with inconceivable rapidity. They raised such a whirlwind of water in their course that it was impossible to distinguish them clearly. A hundred whales of the largest size could hardly have dashed up the ocean waves more violently.

"_Anda, anda!_" (quick, quick), shouted Thalcave, in a voice like thunder.

"What is it, then?" asked Paganel.

"The rising," replied Thalcave.

"He means an inundation," exclaimed Paganel, flying with the others after Thalcave, who had spurred on his horse toward the north.

It was high time, for about five miles south an immense towering wave was seen advancing over the plain, and changing the whole country into an ocean. The tall grass disappeared before it as if cut down by a scythe, and clumps of mimosas were torn up and drifted about like floating islands.

The wave was speeding on with the rapidity of a racehorse, and the travelers fled before it like a cloud before a storm-wind. They looked in vain for some harbor of refuge, and the terrified horses galloped so wildly along that the riders could hardly keep their saddles.

"_Anda, anda!_" shouted Thalcave, and again they spurred on the poor animals till the blood ran from their lacerated sides. They stumbled every now and then over great cracks in the ground, or got entangled in the hidden grass below the water. They fell, and were pulled up only to fall again and again, and be pulled up again and again. The level of the waters was sensibly rising, and less than two miles off the gigantic wave reared its crested head.

For a quarter of an hour this supreme struggle with the most terrible of elements lasted. The fugitives could not tell how far they had gone, but, judging by the speed, the distance must have been considerable. The poor horses, however, were breast-high in water now, and could only advance with extreme difficulty. Glenarvan and Paganel, and, indeed, the whole party, gave themselves up for lost, as the horses were fast getting out of their depth, and six feet of water would be enough to drown them.

It would be impossible to tell the anguish of mind these eight men endured; they felt their own impotence in the presence of these cataclysms of nature so far beyond all human power. Their salvation did not lie in their own hands.

Five minutes afterward, and the horses were swimming; the current alone carried them along with tremendous force, and with a swiftness equal to their fastest gallop; they must have gone fully twenty miles an hour.

All hope of delivery seemed impossible, when the Major suddenly called out:

"A tree!"

"A tree?" exclaimed Glenarvan.