With a wild hurrah Brick ran forward.

“So you were right, were you?” cried the boy. “That really was the Cemetery of the Elephants?”

“Here are the proofs of it,” replied Kyle, relinquishing into Brick’s eager hands the ivory tusk he carried.

“It’s one of the most wonderful discoveries of the century!” affirmed Professor Bruce. “It will create a furor in the scientific world when it becomes known. This alone would have amply repaid me for my trip to this part of the world.”

“To say nothing of the financial value of the discovery,” put in the captain. “The ivory alone in those mounds down there is worth many thousands of dollars. There are scores of the mounds, and each one of them must contain the skeleton of one of the elephants that went there to die at the time that the jungle was much closer to this district than it is now. We dug into four mounds, and in each one we came upon bones and tusks.”

“I’m mighty glad you found the Cemetery of the Elephants!” exclaimed Brick to Kyle. “That’s one object of the trip accomplished.”

“It was merely by accident that I caught sight of the mounds,” replied Kyle modestly.

“Yes,” agreed the professor. “But it wasn’t accident that made you associate your glimpse of them with the Cemetery of the Elephants. Any one less keen might have glanced idly at them, let it go at that, and not even thought of mentioning it. No, the discovery rightly falls to you, and when I reveal the matter to the world I’ll see that you get full credit for it.”

For the rest of that afternoon there was jubilation in the camp. Professor Bruce especially was in the seventh heaven of delight. It seemed to him at times that he must be in a dream. But the sight of the ivory tusks proved that it was far more substantial than any dream.

“Well, now that we’ve made the find, what are we going to do about it?” asked Captain Kane later on, as they sat at their evening meal.

“I know what I’d like to do,” replied the professor. “If we had nothing more important on hand”—he glanced kindly at Brick—“I’d like to settle right down here, explore every feature of the phenomenon and write my treatise about it right on the spot. But all that must wait until we’ve done all we can to rescue Mr. Allison.”

Brick looked at him gratefully.

“And after that?” asked Kyle inquiringly.

“After that,” declared the professor, “we’ll make a careful map of this place, get its exact latitude and longitude, and then return to Tuggurt. There we’ll organize a big expedition, bring along some motor trucks made on the same principle as these cars, exhume the ivory, and have it sent to America. Some of the tusks we’ll give to museums and scientific societies. The rest we’ll dispose of for what they will bring. And we’ll divide what profit we make among all the members of the expedition. And when I say that, I mean that you, Alam, and you, Abdullah, shall share and share alike with the rest. You’re taking your part of the risks of this expedition, and it’s only fair that you should share in the gains.”

Abdullah grinned from ear to ear, and Alam bowed with grave dignity.

“The master is generous,” he said.

“Not at all,” disclaimed the professor. “Only fair.”

It was really more than fair, for it was going beyond custom, and the Arabs were already being well paid for their services. But the professor, and the captain as well, were accustomed to act on a broad-gauge scale.

“Well, leaving that matter for the present,” said the captain, “let’s come to a decision on the subject of the cars. We’ve gone just about as far as we can go with them, and during most of the rest of the time we’re in these wilds we’ll have to go on foot.”

Kyle and Brick looked at each other in dismay.

“I’ve known for the last day or two that we’d have to do it,” said Captain Kane, addressing himself especially to Kyle. “And I’ve been looking around, as we came along, to find a good place in which to hide the cars. But I’ve seen nothing that suited me until to-day. That’s another thing for which we’re indebted to you, Kyle.”

“I don’t see where I’ve had anything to do with it,” replied Kyle, in some surprise.

“Indirectly, of course,” replied his uncle. “But if we hadn’t gone down into this valley as a result of your discovery, we wouldn’t have seen the place I’m referring to.”

“So you found a cave down there?” asked Brick.

“One that seemed to be made for us,” was the reply. “Plenty large enough to hold all the cars, and so hidden naturally by sage brush and cactus that it was only when I accidentally fell and slid through some of the bushes that I discovered it.”

“Perhaps whatever people there are in this district know of it, too,” suggested Kyle, a little uneasily.

“Possible, of course,” assented the captain. “But there were no traces of human habitation, no ashes from fires or anything of that kind to indicate that it had been visited for years. The valley is absolutely a desert, without date trees or water, and there’s no inducement for anyone to go into it.”

“There’s one other thing,” put in the professor, “that would keep the tribesmen away from it, and that is the fact that the elephants’ tombs are there. There’s an old tradition that the ghosts of the elephants walk at night. Probably people avoid the place as they would the plague.”

“So much the better for our purpose,” laughed Kyle. “This is one of the times when I give three cheers for superstition.”

“We’ll get the cars down there the first thing in the morning,” decided Captain Kane.

“We’ll have to be mighty careful in doing it, for the slope is steep, but I’m sure we can make it all right!” exclaimed Kyle joyously.

As soon as the first streaks of dawn showed on the horizon the travelers snatched a hurried breakfast and started the cars on what was to be their last trip for some time to come. Great care was necessary in making the descent, but at last the cars came to a stop at the place the captain indicated.

He had not exaggerated the advantages of the cave as a hiding place, for the boys looked for it in vain until the captain took the lead and pushed aside the bushes that concealed the opening.

By the aid of their flashlights, they explored the place, which was a natural opening into a beetling cliff. It ranged in width from twenty to thirty feet, and ran in for sixty feet or more. It was admirably adapted, not only for concealment, but also, in case of discovery, for defense, as a few determined men by the aid of boulders that stood near and could easily be gathered in time of need, could stand off assailants many times their number.

No track of man or beast could be discovered in the vicinity or on the floor of the cave, which looked as though it were covered with the dust of ages.

“What do you think of it?” asked Captain Kane of the boys.

“Fine!” declared Brick.

“Dandy!” pronounced Kyle. “It couldn’t be better for our purpose. But it makes me feel bad to have to leave the cars. They seem like old friends.”

“And mighty good friends they’ve been to us,” replied his uncle. “But we’re up against hard necessity, and we have to yield to it. I hope we’ll be in them again soon, and with Mr. Allison on one of the front seats.”

It was a hard problem to decide what to take from the cars and what to leave behind. The searchers did not want to burden themselves too heavily, and yet they had to take along with them the absolutely necessary things they required. First among these, of course, came food and water, their guns and ammunition. These alone would prove heavy burdens in that hot climate. What would they not have given to have had a camel at their disposal!

The machine guns were abandoned with the most reluctance. One of them in case of need might be worth a dozen men. They looked at them longingly, but had to give up the idea on account of their weight.

But they did add to their ammunition a dozen hand grenades of the most powerful kind. At close range, they were terribly effective weapons. And nobody knew how soon they might have to use them.

At last their preparations were completed, and they set out with burdened shoulders, and also with burdened hearts. For none of them was under any delusion as to the added danger that confronted them now that they were on foot. Against mounted enemies they would be at a special disadvantage. They could neither pursue them nor run away from them.

Nor could they travel as fast and as far in their search for Mr. Allison. They could only make a few miles a day, and would have to stop frequently for rest. The greater part of their traveling would have to be done very early in the morning and very late in the afternoon and evening.

For these disadvantages, however, there were some compensations. On foot, they would not be so conspicuous to prying eyes as though they were in the cars. And then, too, they could go where cars could not. Also, they could move more noiselessly.

Before they started, the captain distributed some kola nuts among them.

“We’ll have to be as sparing with the water as possible,” he said, “and to some extent these will take the place of it. When you are very thirsty, put one of these in your mouth and keep it there. It’s surprising how they satisfy thirst.”

They had gone several miles, and their loads were becoming intolerably heavy, when suddenly Kyle, who was in advance, made a gesture and dropped flat on the ground.

Trusting in Kyle’s judgment, the others instantly did the same.

[Chapter 19 Maze: Help Kyle Escape]