There was no need of urging haste in the packing for all were eager to get away from the proximity of the men who constituted the greatest peril the party in search of Mr. Allison and the Cave of Emeralds had yet met in the desert.

In less time than Kyle had believed possible, the party was ready to start. The route that Alam had in mind made it necessary for them to go back for a distance of about three miles over the path they had traversed. There they turned sharply to the left and took up their journey over a rough forbidding road that fully justified Alam’s description of it.

But the Americans were in no mood to be critical, and they kept along, though at a greatly diminished rate of speed, owing to the boulders that strewed the district and required the utmost skill in driving to avoid.

Darkness came, and camp was made for the night, the captain and the professor relinquishing the idea they had first entertained of traveling at night in that perilous region, for the way was hard enough to traverse in the full light of day.

The first streak of dawn, however, found the travelers on their way, and now they found that the worst part of the route lay behind them. The way broadened out into a sandy plain where the ground was hard, and they bowled along at a rapid rate.

Their compass told them that they had described a wide semi-circle that had certainly put them far to the front of the robbers’ caravan.

“Now let them follow,” laughed the captain, at their first stop for a meal. “A stern chase is a long chase.”

“Still, we want to remember that we are not yet out of the woods,” said the professor, with a smile. “If I can use that expression in this desert waste. Those fellows are not going to give up the chase so easily.”

“And if they don’t catch us going, they’ll lay for us coming back,” put in Kyle.

“Oh, it’s quite possible that we haven’t seen the last of them,” agreed the captain.

“Gazo el Beno will keep to the trail,” warned Alam. “His heart is hot with the hope of gain.”

“So that’s the leader’s name, is it?” said Kyle. “Well, Gazo el Beno would better give this party a wide berth unless he wants his bones to rest with those of his fathers.”

“I’m getting pretty well fed up with him and his gang myself, and the next time we meet, my finger may be a little careless with the trigger,” added Captain Kane.

“Look!” exclaimed Kyle suddenly. “What is that over there? It looks like a big lake.”

“Impossible!” declared the captain, as he followed the direction of Kyle’s pointing finger. “There’s no lake within hundreds of miles.”

Yet his skepticism was shaken for a moment, for far off, near the horizon, was what seemed to be a large body of water, the movement of the waves being plainly discernible.

“Seeing is believing,” he muttered, as he rubbed his eyes and looked again.

Professor Bruce, who had been observing the phenomenon, shook his head.

“No such luck,” he said, with a smile. “What you’re looking at is a mirage. They’re often seen in the Sahara.”

“Then it isn’t water, after all!” cried Brick, in great disappointment. “It’s just old Nature fooling us.”

“Something like that,” agreed the professor. “It’s a mere optical illusion, due to the varying density of the strata of air. The air is hottest near the sand; the rays coming down from the sky are bent upwards; the eye receives an impression resembling that produced by the reflection of sky light from water. And what renders the illusion more perfect is the flickering, due to the air currents, which causes an appearance like a breeze playing over water.”

“I see,” said Brick, who, however, did not see quite clearly, but was willing to let it go at that.

“I confess that for a moment it had me guessing,” admitted the captain. “But now that our hopes of getting a bath are dashed, suppose we get going once more.”

The illusion persisted for hours, and it grew so tantalizing that after a while they turned their eyes away from it and fixed their attention wholly on the road.

Fortune favored them, and they made good time for the next two days, the cars behaving perfectly.

At Insalah they found one of the largest oases they had seen since the start of their trip. And here for the first time, except for the little trickling springs, they had the refreshing sight of flowing water. There were hundreds of wells, and the water from these was conducted through troughs and ditches to the foot of the many palm trees, thus furnishing irrigation for the dates that were grown there in great profusion.

They found here also one of the gasoline stations that the French had established in the desert, and were able to fill their tanks to the limit and also replenish their stores of water. They made the most of their opportunities, for it was the last place of any importance that they would meet before reaching the Hoggar Plateau.

The French officers, here as everywhere, were most hospitable, and urged the Americans to prolong their stay. But they had to decline, for to their other reasons for haste was added that of Gazo el Beno and his gang of rascals plodding along somewhere behind them in the desert.

The country now was changing. The flat expanse of the desert was being replaced by rocky elevations that grew ever higher and higher as they proceeded. The nights grew colder, and often, after a day of sweltering heat, they were glad enough to seek the protection of the despised blankets that had seemed so needless a part of their equipment.

Vegetation, too, became more abundant. Clumps of sagebrush and cactus made the desert resemble some parts of Arizona. And with these evidences of plant life, however dwarfed and stunted, came traces of game. Jackals disturbed the camp at night with their howling, silenced in more cases than one by a shot from Kyle’s rifle.

They caught sight at times also of gazelles and foxes, whose skins the captain was very anxious to obtain for his collection. Several times, when the party was resting in the heat of the day, the captain and Kyle would sally forth for an hour or two and come back with spoils.

On these occasions, they always consulted Alam, for the Arab had what he regarded as an infallible method of foretelling whether the shooting would be good or bad.

“What are the signs, Alam?” Kyle would inquire.

The Arab would take from his pocket two kola nuts, one end of which was more pointed than another. These he would throw in the air. If they fell with both pointed ends toward the thrower, the signs were good. If both sharp ends were pointing the other way, the outlook was bad. If one point was toward him and the other away from him, the process had to be repeated. And the odd thing about it was that the signs were apparently justified. A mere coincidence, according to the Americans, but one that brought profound satisfaction to Alam.

Kyle’s shooting on these trips delighted his uncle. The new rifle worked to a charm. Up to that time, most of Kyle’s marksmanship had been developed at stationary targets. Now he had an opportunity of perfecting himself in shooting at moving objects, and more than once he brought down his quarry with a shot that the captain himself could scarcely have bettered.

“Good work, my boy,” congratulated his uncle, on one occasion when Kyle brought down a jackal that had almost got out of range. “That kind of shooting is going to come in mighty handy, if the Tuaregs try any of their funny business on us.”

The third day out from Insalah, Alam pointed to a thin blue line on the horizon.

“The Hoggar Mountains,” he announced.

A thrill went through the members of the party. Now they were close upon the objects of their expedition. Somewhere in this vicinity, if anywhere, they might hope to find the man of whom they were in search, if he were still alive. Somewhere on this great plateau or in the depths of the mountain ranges might lie the Cave of Emeralds. Somewhere in the same district they might have the luck of coming upon the City of Brass. And of special interest to the professor, was the chance of finding the mysterious Cemetery of the Elephants.

Now especial care was necessary, for the plateau was the dwelling place of the Tuaregs, the fierce desert folk that lived on plunder. And the searchers must contemplate the probability that before long they would have to abandon their automobiles and proceed on foot. This would greatly increase the dangers to which they would be exposed, for in case of attack the cars were so many small forts that afforded no mean protection. And when all was said and done, the fact remained that there were only six in the party.

But their hearts were stout and their weapons good, and although they realized their danger more clearly than they had before, there was no faint-heartedness or wavering. They had put their hands to the plough and would not turn back.

The party proceeded now with great caution, keeping the cars much closer together than they had been in the habit of doing. The use of the horn was abandoned, lest the sound should reach hostile ears, and their eyes ranged the landscape, intent upon discovering the first sign of danger.

Brick, especially, was on the alert. He was traveling in the vicinity of the place he had been when the caravan with which he was journeying had been raided. Suddenly he gave vent to an exclamation and clutched Kyle’s arm.

“This is the place we were camping when the Tuaregs came down upon us!” he cried, pointing to a small plateau. “And there, on the side of the hill, is the rock behind which Alam and I were hiding.”

[Chapter 16 Maze: Help Kyle Escape]