JOE’S first impulse was to get to his feet and utter an exclamation of alarm. But he knew that this sudden movement might cause the creature, whatever it was, to rush at him.

His rifle lay at his side for just such an emergency as this. Thankfully Joe raised the gun, took aim, and fired between those two lights, which had now taken the form of eyes.

Bang! The shot broke the stillness of the night and sent Bob and Dr. Rander scurrying over to their friend. They had been on the opposite side of the fire and had not noticed Joe’s movements.

“What is it?” Bob was all excitement.

“Don’t know,” his friend replied. “Let’s see.”

The sound of the gun had not been followed by any other noise. Evidently Joe’s aim had been true, killing the creature instantly.

Bob produced a flashlight, which he turned in the direction in which his friend had fired.

“Why—it’s another snake!” exclaimed Dr. Rander. “A bola. It isn’t poisonous, but it is a good thing you got it. There is no way of knowing what it might have been.”

With the aid of the flashlight they examined the reptile closely. Its head was almost shot off, making it useless as a specimen.

“I’d like to have it for Dad and the other naturalists,” remarked Bob. “But as it is, guess it’s no good for anything.”

“You should have been more careful in shooting it,” teased Dr. Rander. “Now if you had aimed at its body instead of its head——”

Joe smiled.

“A snake has eyes in only one place,” he said laughingly, “and the eyes are the only part of it you can see at night. Now if this fellow had worn a badge to signify that he was a member of the Royal Order of Andean Reptiles, maybe the fire shining on it would have given me a good place to take aim at.”

“Probably wouldn’t bother with him anyway,” said Bob. “After all, we’re out to find the treasure.”

Nothing happened that night to disturb their slumber. They awoke the next morning eager to continue the journey.

“Today we should come to the big secret,” Dr. Rander told them during breakfast. “If all goes well, we should get there this afternoon.”

Bob was restless.

“Let’s hurry and get going,” he urged, untying the mules.

Farther over the rocky trail the three adventurers trudged, keeping a sharp lookout for anything unusual.

Always in the distance were massive snow-clad peaks, which on this morning were enshrouded in a heavy mist. Usually they were plainly visible, especially through the high-powered binoculars that were carried by Joe.

Gradually the path spiraled down the steep slope until it passed through a narrow valley, which was green with a variety of luxuriant vegetation. So dense were the plants that they almost formed a jungle.

“Look at this,” cried Bob, moving over to a vine that was laden with large red berries. “Wonder if they’re good to eat?”

“Yes.” The old man had broken off a branch and was eagerly partaking of the fruit. “They are wild cherries, or tomatoes, as some call them. There is nothing better for taste.”

“Right you are!” agreed Joe, after he had eaten several of the berries. “They’re fine!”

They picked a sackful of the fruit to have at the noon meal. Then they resumed the journey.

At places the trail was overgrown with weeds and grass, making it difficult to follow it. But Dr. Rander had been through this region before and did not hesitate long in picking out the right branch.

“I don’t see how you can remember the way,” Joe told him, when he had pointed out one of three branches, each of which was almost parallel to the others.

The old man laughed.

“I can’t afford to forget,” he said. “All that treasure is something that is worth too much to be forgetting where it is. If it should happen, though, that I should get turned around, I have a rough sketch map of this region that I made at the very start.”

On the other side of the valley was a steep slope that was entirely devoid of vegetation. Look about as the youths did, they could see no path. They were beginning to wonder when Dr. Rander broke the silence.

“From here there is no trail,” he explained. “We’ll have to cut our way through the hard places and climb over large rocks. It won’t be easy, but we will be rewarded.”

“No trail, huh?” thought Bob. “Here’s where the fun begins.”

It was far from fun, in the usual sense of the word. The three labored over short, steep elevations, rocky precipices, narrow ridges, pulling the sure-footed mules behind them. At last, when they finally reached a high ledge, they sat down to get their breath.

“Whew!” gasped Joe, wiping the perspiration from his brow. “I don’t want much of that. Wonder how old Dr. Rander stands up under such a strain?”

“Hardened to it, I suppose,” was Bob’s reply. “Since he left college he’s been nothing else but an explorer.”

The old man had been at the back of the line, attending to the last pack animal. There was a smile on his face as he approached his young friends.

“We’ve made unusually good time,” he said, sitting down beside them, “and we can afford a rest.”

“We earned it, all right,” came from Joe. “How much more of this is there?”

“A long stretch,” Dr. Rander responded. “Several miles, to say the least. Of course,” he added, “it would not be long if we could go in a straight line. But over mountains and around cliffs the going is much different.”

“I’ll say it is!” Joe was still panting from the difficult climb. The high altitude required an unusual amount of wind.

Fifteen minutes later they were ready to continue. The mules had been coaxed ahead over the dangerous ledge.

“Getting darker,” observed Bob Holton. “Wonder if it’s going to rain?”

Dr. Rander looked up anxiously. Sure enough, heavy clouds were forming above the mountain tops, hiding the sun from view.

“It would not be well for us to be caught in a storm here,” the old explorer said. “We must seek shelter somewhere. It certainly looks as if a storm will be upon us before long.”

They looked about for some place of refuge, such as a cave or overhanging rock. But luck was not with them that day. They had searched an hour under a sky that was rapidly becoming darker when suddenly a terrific hailstorm struck them.

“Quick!” gasped Joe, who was almost frantic. “We must find some place!”

“We’re not finding it,” returned his chum, who was taking the danger more lightly. “And I guess there’s nothing we can do but stay out here in the open and endure it.”

But a few minutes later Bob had become as serious as his friend. Hail as large as marbles was falling with a terrible velocity, striking the explorers’ faces dangerously. One lump caught Joe squarely on the nose, causing him to utter a cry of pain.

“This is awful!” he moaned, holding his hand in front of his eyes.

How long the storm would last they had not the faintest idea. Even Dr. Rander could express no opinion.

Doggedly they fought off the hail, which bruised and cut their faces and bodies. They wondered how the mules were standing it. Could the animals endure the terrific onslaught? Or would they become panic-stricken and plunge off the steep cliff?

After what seemed like hours, the hailstorm suddenly subsided and the sky began to lighten. Ten minutes later the surrounding mountains bore no evidence of the disturbance.

With the adventurers, however, it was a different matter. Their faces were cut in many places, and their clothing was torn. A more miserable-looking trio could hardly have been found.

“Get out the ointment,” directed Bob. “We’ll sure need plenty of it.”

“The mules came through all right,” observed Dr. Rander. “Cut and bruised, but nothing more.”

“It’s funny,” began Joe, looking up at the sun, which was now in full view. “That was a very queer storm. It came quickly and ended the same way.”

“Hailstorms are rather common in this part,” explained the old man, getting out a box of antiseptics and first-aid remedies.

Their numerous wounds were treated with a soothing salve. Then, after looking over the mules, they moved on around the mountainside.

At a huge notch in the rocky slope they stopped to examine a curious formation that puzzled them. It was a long sloping slide, running gradually down the mountainside. From all appearances it was as smooth as glass.

“I don’t know whether this is natural or man-made,” said Dr. Rander. “I never have been able to find out. But,” he went on, “what concerns us is that we’ll have to slide down to the foot of the mountain.”

“What!” Bob’s surprise was beyond words. “Do you really mean that?”

“Every word of it,” was the old man’s reply. His little eyes twinkled. “Don’t you think much of the idea?”

Bob laughed.

“It was so sudden that I hadn’t given it a thought,” he answered. “But”—gazing far down the smooth slope—“it looks rather inviting. Will you go first?” The youth was not fully convinced that Dr. Rander was in earnest.

“If I go, one of you will have to stay with the pack animals,” the old man said. “I don’t think they had better try it,” he added with a laugh.

Bob and Joe looked puzzled.

“I don’t understand,” said the latter, hesitating. “Do you mean that some of us will slide down this slope and some stay with the mules—leave them here, I mean?”

“Oh, no,” smiled Dr. Rander. “One of us will have to take the mules down the trail. We could all go that way, but as it is very long, this offers a short cut that you fellows can take. That is, if you want to. When you get to the bottom you can wait until I get down the trail with the pack animals.”

“Where is the trail?” Bob secretly wondered if Dr. Rander had suddenly changed his mind about sharing the treasure with them and was using this means to evade them. He did not think the old man treacherous, but he wanted to be on the safe side.

“Over there.” Dr. Rander pointed to a narrow path that circled down the mountainside.

“Suppose,” Bob began, “you and Joe go down the slide while I take the mules down the trail. I don’t like the looks of that glassy slope.”

“All right. I’m no longer young, but I still like sport. Here I go.”

The next moment he was sliding rapidly down the polished incline.

When he was halfway down, Bob and Joe burst out in laughter. The sight of the old man doing such a thing as this with so much enjoyment aroused the youths’ sense of humor.

“If he likes it so much, maybe I will,” chuckled Joe, sitting down at the edge.

“Good luck,” called Bob, as his friend let go his hold and passed swiftly down.

It was an unusual sensation to Joe, as he shot down the curving slide. When younger he had often played on the slides in parks. But this was something entirely different. To shoot down a tall mountain at a rapid pace, on the straightaways and around curves, was indeed novel.

When over halfway down, the youth felt himself gradually lose momentum, and he knew that the slide was flattening out. Too steep a descent, especially near the bottom, would be dangerous.

At last he came to a stop beside Dr. Rander, who had been watching the descent.

“How did you like it?” the old man asked.

“All right. Got rather warm, though. Wonder if it thinned my trousers any? No, I guess not. Too smooth, I suppose.”

Fifteen minutes later Bob came in sight leading the line of mules. He laughed as he caught sight of them.

“Any worse for your experience?” the youth asked with a chuckle.

“Do we look it?” smiled Joe. “We enjoyed it.”

As the sun was almost directly overhead they decided to remain at this spot for the midday meal. All were extremely tired and hungry.

Bob prepared dinner, using water they had brought with them in canteens. As a dessert they feasted on the delicious wild cherries that they had picked that morning.

“Now let’s get going,” urged Joe, when the meal was over. “I’d like to see that treasure.”

Farther into the wilds they plunged, with not the faintest suggestion of a trail to guide them.

“No trace of any vegetation here,” observed Bob. “It’s a good thing we stopped where we did, or the mules probably wouldn’t have had anything to eat. There were a few stunted bushes and other plants back at the foot of the slide.”

An hour of climbing brought them to a place where a tall peak obstructed their view.

They trudged around and then suddenly found themselves at the bank of the roaring Apurimac River.

“On a little farther,” Dr. Rander said, urging the mules to ascend the difficult slope.

At last they came to a place where a high rock protruded far over the river. Here the old explorer called a halt and pointed up the side of a mountain.

“In that little notch up there is the entrance to the treasure,” he said. “As I said before, there is a huge cave that occupies the entire mountain. There we will find the treasure, if there is any.”

The youths’ hearts beat rapidly. They could hardly believe that at last they were nearing the great secret.

“But,” hesitated Bob Holton, “how are we going to get across this roaring river?”

“That,” the old explorer returned, “will be the most difficult part of our entire journey. Come. Let me show you.”

They followed him to the edge of a high rock that protruded far out over the seething rapids.

“Look there,” he said, pointing to something.

Stretching from the rock across the river to another protruding crag was a heavy metal wire, which, strange to say, showed not the slightest trace of rust.

“That cable was put there by the Incas,” Dr. Rander said. “It is hundreds of years old, but still looks as if it had been built but yesterday. It is coated with some secret preservative, which prevents it from rusting through.”

“Interesting,” remarked Joe. “But what about it?”

The old man replied at once.

“We must cross the river by hanging from the cable with our hands,” he said quietly.

Joe’s heart sank. Secretly he felt that if he were to undertake the dangerous venture he would meet with tragedy.