TO the two boys, who had hoped against hope that their parched throats could be relieved, the priceless water tasted like nectar. They had felt sure that grim tragedy was near. Now their spirits were restored to a new high level, and they considered themselves equal to anything.

At last, when they had fully quenched their thirst, they glanced about the cavern.

Near the edge of the pool were the tracks of wild animals, which had evidently made this place a frequent haunt. The youths did not recognize all the imprints, but Joe stoutly declared that gazelles had been there.

“Doesn’t seem pleasant to know that we’ve been drinking after wild animals, does it?” laughed Bob.

“No. But we won’t think of that, especially since our thirst was so great. Then, too, it’s not likely that many germs are to be found away out here in the desert mountains.”

The youths stretched out on the cool white sand beside the pool. The atmosphere in the cavern was such a departure from the fierce outside heat that they were content idly to while the time away, despite the fact that they should be getting back to camp. At times they bent over to drink of the refreshing water, delightfully knowing that they could have all they wanted.

Then they grew drowsy and gradually fell asleep, a thing that they should not have done.

At last they were awakened—suddenly! Every nerve in their bodies seemed tense. Something told them not to move.

Slowly they edged around and looked toward the back of the cave. Then they started, as a savage growl rent the air. A fierce tiger cat was crouched ready to spring. It had evidently come to the pool for water when it had discovered the youths.

There was no time to take aim with their rifles, for the beast would be upon them.

Slowly Bob reached for his pistol, and Joe followed suit. At last the boys were ready for action.

With a quick motion Bob whirled about and took hasty aim; then fired. A second later the report of Joe’s gun rang out.

“Missed!” cried Joe in horror. “Both shots missed!”

“Well, we won’t miss again,” said Bob, gritting his teeth. “We’ve got to stop him.”

Bob jumped to his feet and took aim. Five shots followed in rapid succession. Joe continued the defense with his revolver.

When the deadly fire ceased, the tiger cat was literally riddled with bullets. It gave a convulsive twitch and rolled over, dead.

“Finally stopped him,” muttered Joe, his face wet with perspiration. “And a powerful fellow, too.”

“One can do a lot of things if he has to,” remarked Bob, putting his gun back in its holster.

The youths lost no time in getting out of the cave. They would have liked to remain in its cool retreat much longer, but they realized that it was necessary to get back to camp.

“Won’t our dads and the others be tickled beyond words when we tell them we’ve found water!” smiled Joe, as they crawled through the narrow passageway.

“Tickled is too weak to describe it,” said Bob. “I bet old Tishmak will hug us to death.”

At last they reached the outside and turned their footsteps toward camp. It was but a short distance away, beyond the tall precipice at the entrance to the cave. The youths put unusual energy into their legs and in but a few moments were met by all of their friends. Their fathers, in particular, rushed forward anxiously.

“Where have you been so long?” demanded Mr. Holton, vexed to the utmost that the young men should stay away from camp for an indefinite period without giving an explanation of where they were going.

Joe’s father’s temper was also wrought up.

“Did something hold you back?” he asked.

“Yes,” Joe answered quietly. “Several things kept us from returning sooner. But it may interest you more if we tell you that we’ve found water.”

“Water!” Mr. Lewis was all excitement. “You mean—you actually have located a well?”

Mr. Holton and Dr. Kirshner listened breathlessly. Fekmah translated joyfully to Tishmak.

“Not exactly a well,” returned Bob, “but something just as good. An underground pool. And how cool it is! Come on,” he added. “I know you’re all dying for a drink.”

Hastily the men followed their young companions over to the large cliff. Then, after crawling through the small opening, they found themselves at the edge of the pool of bubbling water.

For a moment the men could hardly believe their eyes. At last! Water!

Suddenly, as though urged on by some unseen power, they bent down and drank until they could hold no more. It was pleasure unthinkable!

At last Dr. Kirshner straightened up.

“I’ve never had such enjoyment in years,” he said happily, and then added: “Lucky that our thirst was no worse than it was, or it would have been necessary to restrain ourselves from drinking too much at once.”

When the men had finished drinking, they glanced about the cave. Their flashlights fell on the body of the tiger cat, and they looked up in surprise.

“What’s this?” inquired Mr. Lewis, pointing to the bullet-riddled carcass.

Bob and Joe smiled.

“That old boy tried to make us remain for dinner, but we fooled him,” explained Bob. “We had to empty our revolvers to stop him, though.”

There was a clamor of excited questions, and the youths were forced to relate every detail of the encounter. When they had finished, the naturalists bent over to examine the striped skin.

“Too bad, but I’m afraid you’ve put too many bullets in him for us to use the skin,” said Mr. Holton regretfully. “And a large specimen, too. But then,” he went on, “we won’t think of that when your lives hung in the balance.”

The explorers spent a few minutes sitting in the cool white sand. Then they went back outside to get the water containers.

They had had an uneasy feeling that perhaps the camels had been molested during their stay in the cavern, and gave a sigh of relief upon seeing them sitting peacefully near the tent.

As it was getting late, camp was broken, and the dromedaries were led to the entrance of the cave. The water containers were carried in to the pool and filled to capacity with what stood between the explorers and death.

“Now that everything is in readiness, I suppose we must be getting on our way,” said Dr. Kirshner. “But I must admit I hate to leave that pool behind. Somehow I’ve become greatly attached to it.”

“Does seem too bad,” Mr. Lewis agreed. “But I suppose we will find other wells and sources of water. Where is the next one, Fekmah?”

“Many miles away,” the Arab returned. “But come to think of it, Tishmak says one around here near. If it very far away, we go to it.”

When the question was put to him, the guide replied that the well was but a few miles away. He considered it unnecessary to find it, as another was a day’s journey in their direction. He informed them that since it was very large, it could not be easily covered up by the two thieves.

With one last look at the high precipice, the explorers turned the camels back on the lane between the mountains. With the right kind of luck they would come to the gorge of Arak some time the next day, and another landmark on Fekmah’s duplicate map would have been noted.

As they penetrated farther into the mountains, the scenery became more beautiful. There were many wonders that caused the explorers to gasp in astonishment.

“The Ahaggar range is of larger extent than the Alps,” said Dr. Kirshner, as they circled about among the rugged cliffs. “And although not of extremely high altitude, these Saharan mountains have many show points that cannot be found elsewhere.”

“And they are comparatively unknown to the outside world,” put in Bob. “Why, the average person doesn’t even dream of mountains being in the heart of the old Sahara.”

All along the way Bob and Joe took motion pictures of the many strange marvels of nature. They photographed the tall peaks, the deep gorges, and the narrow valleys. They turned the cameras on the many ancient inscriptions that were of so much interest to the archÆologist.

“We’ve run off a good many hundred feet of film,” remarked Joe, after the cameras had “purred” for an unusually long period as the youths filmed a deep canyon through which they passed. “In fact, if they had given us twice as much film we could easily have used it all.”

Bob nodded.

“And there’s less danger of losing it in a hot, dry region like this,” he said. “Isn’t at all to be compared with the damp, tropical climate of Brazil.”

Slowly the country became more rough, until that evening, after the meal, the adventurers found it very difficult to pick out a way between the many large rocks. On one occasion they passed through a dark tunnel-like passage beneath high, overhanging peaks, and had literally to feel their way through. There was not the faintest ray of moonlight to lighten the deep passageway.

When they finally came to the other end they gave sighs of relief that at last the moon could again be seen. But now something else hindered progress. A peculiar desert plant, with sharp, poisonous needles and a rather disagreeable odor, had been known previously to the explorers. Now, as they emerged from the dark recesses of the tunnel, they came upon large clusters of these plants. Everywhere the dromedaries went, it seemed, they were forced to tramp through these formidable shrubs.

“It’s a wonder they can stand it,” said Joe, shaking his head. “Their feet are already swollen almost double.”

“Be tragedy if the animals would have to stop,” the other youth said. “It would mean our end, I guess.”

“They’ll make it all right,” put in Mr. Lewis, who was riding at the rear with the boys. “But, needless to say, we couldn’t walk on them.”

Suddenly, as they came to the edge of a dry river bed, Dr. Kirshner halted his camel and looked about on the ground. The others waited a moment to see what he had discovered.

“An ancient tool of flint,” he announced, commanding his camel to kneel.

The archÆologist picked up the instrument and examined it carefully with the aid of a flashlight. It was about a foot long and shaped to resemble a crescent. The inner edge was as sharp as a razor.

“Doubtless some kind of a knife,” Dr. Kirshner said, as the others crowded around him. “Shaped out of flint by people of the Neolithic age. Perhaps it was used to harvest crops.”

“Crops? In the desert?” Bob was amazed.

The scholar nodded.

“It is firmly believed that primitive people lived in what is now the desert rather than along river valleys of more modern prominence. Of course the Sahara was at that time much less arid, or dry, than it is today.”

Dr. Kirshner searched about for other relics, but found none.

“It is strange how that tool got on the surface of the ground,” he remarked, as they turned the dromedaries ahead. “Other expeditions have penetrated into this region, and it is quite obvious that they would have found it had it been in sight.”

“Perhaps a rainstorm washed it out of the ground,” suggested Mr. Holton.

They rode until late that night, for they were anxious to come to the gorge of Arak some time the next day.

“We should see it tomorrow afternoon,” predicted Fekmah.

Notwithstanding this, they rode all the next morning without coming to the landmark. Finally Tishmak gave up in disgust and stopped in the shade of an overhanging rock. It was nearly noon, and the necessity to get a meal was becoming more apparent.

When they had finished eating they continued to rest in the tent. At this high altitude the sun was less hot than it had been on the plateaux, and it would have been possible to ride farther. But they had become accustomed to the usual afternoon rest and were loath to depart from this regularity.

But Dr. Kirshner had sat only a few minutes before he got up and stretched. Mr. Holton and Mr. Lewis were asleep, but Fekmah and Tishmak remained awake. Bob and Joe sat in one corner of the tent, sleepily gazing out at the distant peaks.

“I’m going out and look around,” Dr. Kirshner said to them. “Care to go along?”

Bob replied in the negative, but Joe arose and walked over to his rifle.

“Don’t stay too long,” advised Bob, as Joe and the archÆologist started out.

They were familiar with the country in the immediate vicinity of camp. As there was nothing of new interest to be found there, they hiked farther to the south. The scientist wished particularly to find more ancient inscriptions, and, if possible, other evidences of ancient civilizations.

“What’s this?” cried Joe, slapping his hand to his face. “Well I’ll be—— Some kind of a fly.”

“It is a wonder we haven’t come across insect pests long before this,” Dr. Kirshner said. “They are very common all through this section.”

The flies had been discovered while they were trudging through a long, hot passageway between two high wall-like rocks. Now, as the two adventurers passed farther on, they came into more of the insects, which swarmed about as if thirsty for human blood.

“Ought to have some kind of a spray,” remarked Joe, pushing them away in great numbers.

“We have, in camp,” his friend said. “If the pests bother us much we’ll have to make use of it.”

After an hour’s hike they came to another dry river bed, and again Dr. Kirshner found flint implements scattered about. Joe had a small motion-picture camera with him, and at the scientist’s request he filmed the half-buried primitive tools as they lay hardly visible in the sand.

“I want proof that these antiquities came from the Sahara,” Dr. Kirshner said, placing them in the small box he carried over his shoulder for the purpose.

A little later Joe started to take a motion picture of a small animal that darted across the river bed, but cried out in disgust.

“A pesky fly got in front of the lens,” the youth explained. “Looked as big as an elephant.”

“One scene ruined,” laughed the archÆologist. “But you’ll have to get used to that.”

The adventurers stopped here and there to rest and sip a small amount of water. Then they would hike on, always on the lookout for the unusual.

They had just rounded the corner of a tall, cone-shaped peak when Joe stopped and pointed to the sand near by.

Dr. Kirshner’s jaw dropped in surprise.

“Footprints!” he cried. “Human footprints!”

He had hardly uttered the words when there came a chorus of yells from behind a large rock. A moment later ten or twelve rough-looking Arabs darted out and surrounded the Americans. The natives at once disarmed the whites by sheer force and then displayed long knives threateningly.

The Arabs chattered ominous words, which caused Dr. Kirshner to start in alarm and fear.

“We are being captured!” he exclaimed excitedly. “These Arabs are hired by the two thieves who stole Fekmah’s map!”