“ELEPHANTS?” asked Bob, almost bursting out in laughter.

“Come on,” suggested Joe, moving slowly down the side of the fissure. “Let’s have a look at the strange drawings.”

The youths slid to the bottom, where Dr. Kirshner stood staring at the wall.

Bob nodded.

“Drawings of elephants, all right,” he said, his eyes on the etched rock. “And look how plain they are.”

The archÆologist took out his notebook and copied the sketches as best he could. Then he turned to the youths.

“Here is proof that the desert was not always a desert,” he said, his eyes becoming bright with interest. “Thousands of years ago this region was green with tropical vegetation, like the dense forests of East Africa. It was probably inhabited by tribes of people much different from the Arabs and Tuaregs who now live here. Then came a gradual dry spell, and in time the luxurious growth gave way to a hot desert of sand and rocks.”

“Those drawings of elephants, then, were made while this region was covered with forests?” questioned Joe, becoming as interested as the scientist.

The latter nodded.

“Elephants and other wild game probably roamed about here in great numbers,” he explained.

After one last look at the strange sketches, the explorers began the task of climbing up the side of the ravine. It was not easy to pull themselves up out of the steep crevice, but the rocky walls were solid, not even threatening to give way.

Then followed an hour of exploration about the top of the cliff, during which time the archÆologist came upon the remains of many other ancient drawings and inscriptions. By the time that they were ready to begin the descent of the cliff, he had filled his notebook.

“But when we get to the Ahaggars we’ll undoubtedly find many more,” he said, slowly leading the way down.

After what seemed a long time, they came to the bottom of the precipice and lost no time in getting back to camp.

“Have any luck?” asked Mr. Holton, looking up with interest as the three explorers moved toward the tent.

“Did we!” laughed Joe and proceeded to tell of the many drawings and inscriptions.

“You boys should have taken the motion-picture cameras with you,” Mr. Lewis said. “They would have furnished proof to the outside world.”

“Perhaps we can yet,” said Joe.

“No, you can’t,” protested Mr. Holton. “We must not waste any time here, if we are to find the hidden riches. Right now,” he added, “you three had better turn in and take your afternoon rest. That sun is terrible!”

Dr. Kirshner and the youths did as suggested, glad to rest their tired limbs. But they were up promptly at three, packing the tent and provisions on the dromedaries.

Now, as they continued farther toward the barren mountains, they began to realize what thirst really meant. As Tishmak had told them, no well would be reached until late the next afternoon, and their water containers were none too full. Their throats were parched, and their tongues began to feel numb. The fierce sun seemed all the hotter, greatly stimulating thirst.

All through that day they rode onward, the Ahaggars gradually becoming nearer. It was late that night when they finally stopped and camped in a wild region of large red rocks.

The next day their thirst became almost overpowering, even though they did not exercise. It seemed that they could stand it no longer, but they rode continually on toward the well that was located at the foot of the mountains.

The noon meal was almost without water. They did, however, sip a small amount of the precious fluid.

“Oh, if we could only drink all we want!” groaned Joe, hesitating to eat the beans that had been prepared. “Everything is so dry without water.”

But although the explorers were extremely anxious to come to the well, they gave full consideration to the midday rest. It would have meant destruction to ride under that terrible desert sun.

“Before long we’ll come to the well,” said Fekmah, as they prepared to continue the journey. “In an hour it be seen.”

“And how glad we’ll be,” muttered Bob, anticipating the pleasure of drinking a large quantity of the refreshing fluid.

The hour passed slowly. They were looking about now, searching among the many huge rocks.

Suddenly Tishmak halted abruptly, and the expression of hope that had been on his face changed to one of fear. He motioned for the others to move on up to where he was.

No translation of his excited words was necessary to the Americans. They understood his anxiety. The well was dry!

For a moment the explorers sank back, and fear—stark fear—seized them. Thoughts of disaster haunted their stricken brains—stories of how large trading caravans had been brought to a tragic end because of no water. It was torture unthinkable!

“And after all this waiting,” groaned Bob, his hope almost gone.

The others were equally touched. Now that they had met with defeat, they felt at a loss to know how to carry on.

As a last resort Tishmak had fallen into a convulsion of motions asking Allah that they might be delivered from the jaws of death. His enthusiasm grew more intense with every moment, becoming almost disgusting to the others. Even Fekmah, although he was a devout believer in Mohammedanism, thought the actions of his fellow countryman detestable.

“Come, now,” urged Dr. Kirshner, using his knowledge of the native language to console Tishmak. “We’ll come out all right. This isn’t the only jam we’ve been in.”

The guide finally became his natural self, although still a bit panicky.

“You’d think after all the expeditions he’s led into the Sahara he would be calm in the face of danger,” remarked Bob.

“Danger, yes. But not in the face of tragedy!” thought Dr. Kirshner, although he said nothing. He feared all too much that this might be the end.

“Where is the next well?” asked Mr. Lewis calmly.

Fekmah put the question before the guide, who replied that there was no water within a distance of fifty miles. And mountains lay directly before them, hindering travel. It might mean a several days’ journey before they would come to the well, and then there was a possibility that it, also, was dry. Disaster seemed almost inevitable!

“But let’s hurry on,” said Mr. Holton. “Perhaps if we make time we can get to it much sooner than we think.”

The camels were urged forward at a fast trot. But before long they were entering the mountains, and the rapid pace was necessarily slackened somewhat.

During that desperate ride against time, the explorers hardly thought of the scenic wonders that lay before them. Indeed if they had not been in such anxiety, they would have seen much to interest them greatly.

Tall, needle-like peaks were all about, grotesque rocks dotted the irregular plateau before them, deep gulches and ravines were everywhere. It was a wonderful view, that beheld by the adventurers, and could have been enjoyed to the fullest had they not been in such terrible plight.

Luckily there was a full moon that night, lighting the vast expanse with a weird brightness. Countless stars shone down from the clear sky, appearing so close that they could seemingly be touched.

“Like we’re in another world,” breathed Bob, as he and his chum rode rapidly at the rear of the pack camels.

“Does seem strange, doesn’t it? I wonder if we’ll live to find the hidden riches?”

“Of course we will.” Bob cheered his friend as best he could, and himself felt much the better for it.

Luck was with them that night. The plateau remained open and free from peaks and rocky crags that would have delayed progress. It was, however, very unlevel, and the dromedaries often found it necessary to slow down to a difficult walk.

It was very late when they finally halted and made camp under the beautiful mountain sky. After a brief supper, at which almost the last drop of water was used, they fell asleep, not to awaken until the sun was well up in the sky the next morning.

“You know,” remarked Fekmah, “it seems strange that that well was dry. I been thinking about it since we left it behind. Tishmak too thinks it strange.”

“Why?” questioned Mr. Lewis, sensing that something was in the wind.

“Because,” Fekmah said gravely, “it a large well, and should not go dry much easy. Tishmak think it been covered up.”

There were exclamations of surprise from the Americans.

“You mean,” began Mr. Holton, beginning to catch the point, “that someone did it to keep us from continuing the journey?”

“Yes. I think it might have been the two thieves who stole my map. They did it to keep us away from hidden treasure.”

There were cries of astonishment from the others. For the past few days the thought of the thieves had been absent from their minds. Now they began to realize that at last they had probably come into the region in which were the hidden riches.

“Then the rascals must be around here some place,” said Joe, looking about sharply. “Perhaps they’re right around here.”

Fekmah got out the map he had made from memory after the original one had been stolen. He studied it closely for a few minutes.

“Hidden treasure still great distance away,” he said at last. “We not find it till several days pass. I think the two thieves not here but somewhere near treasure.”

“What’s the next landmark?” inquired Mr. Lewis, as the camels were made to move forward.

“The gorge of Arak,” Fekmah returned. “It quite a distance from here, but Tishmak lead us to it quickly.”

All morning they trudged on without coming to the well that Tishmak knew was somewhere in the first range of mountains. Although it seemed impossible, their thirst rapidly increased still more.

“Say,” cried Bob, as a sudden thought struck him, “if those two thieves could cover up the first mountain well, they might do the same to others. Wouldn’t it be possible?”

“Not the next one,” returned Fekmah. “It too large. Take many, many men to stop it. But there are several small ones farther on that could be covered.”

At an hour before noon it was necessary to stop for the daily rest, even though they would have liked to continue in search of water.

They were in a narrow valley between tall, sharp peaks. A ribbon-like dry river bed wound in and out among the brightly colored rocks, suggesting that once a rushing stream had forced its way through the mountains.

“How I wish the river were still here,” said Joe with a sigh.

As soon as camp was made, the explorers took it easy in the shade of the tent, more than glad to escape the terrible heat of the sun.

But before long Bob and Joe became restless. At last Joe got up and stretched. He sipped a very small quantity of water; then motioned for Bob to get up.

“What’s up?” the latter asked.

“Come on,” said Joe, picking up his rifle. “Let’s go out awhile. I’m anxious to explore these mountains around here. There’s no telling what we may come across.”

Bob was willing, and as the sun was slightly less hot, they started out in the direction of a large mountain that had tall, sharp points reaching up into the sky.

“What’s that over there?” asked Bob, pointing to a wall of rock some two hundred feet away.

“Don’t know. Let’s go over and see.”

The youths walked over to the precipice and then halted before a small crack that looked to be the entrance to a cave.

“Shall we go in?” asked Joe.

“I’m game. Come on.”

The hole in the rock was so small that it was necessary to crawl on their hands and knees for a short distance. Then the cave became larger, and they could stand.

Bob had his flashlight in his pocket and at once switched on the light.

“We’re in a large cave, all right,” observed Joe, casting eager eyes about. “There’s another opening away over there,” pointing to the far side of the cave. “Let’s go through it and see where it leads us.”

The hole was so small that the boys barely got through crawling on their stomachs. But at last they reached the other side, and Bob turned the light ahead.

“Just another cave,” said Bob. “Chances are——”

“Wait!” started Joe, gazing at the darkness before them. “Let’s have some light over there.”

The beam was turned in the direction indicated by Joe, and the next moment the boys gave startled exclamations.

“A narrow passageway,” observed Bob. “Come on. We’ll see where it takes us.”

Suddenly, as they rounded a sharp corner, the youths came face to face with something that made them cry out in delight.

There, directly before them, was a large underground pool of sparkling water.

With a word of thanksgiving the young men rushed over and gulped up large quantities of the precious fluid.

“At last!” cried Bob, too happy for words. “At last we’ve found water!”