“WHAT’S going on?” cried Joe Lewis, as a chorus of voices mingled with the sound of rifle shots.

“Some trouble somewhere,” returned Bob. “Wonder——”

He did not finish, for at that instant there came another shot, and a bullet whizzed by his ear.

The youths lost no time in hiding behind a small mud hut, although they knew a bullet could probably penetrate it. But at least it offered temporary shelter, and that was what they wanted.

“Look!” cried Bob, gazing cautiously around the corner of the hut. “There are soldiers in uniform. What do you suppose they’re doing?”

They were soon to see.

The troops, which numbered about thirty, were firing at something that the boys could not see from their places at the side of the hut.

“I’m going to take a chance and get out in the open where I can see something,” said Joe. “Come on. If we’re careful and don’t get in the way of the shooting, we’ll be all right.”

Carefully the chums edged around the side of the dwelling and peeped out at the street. Then they drew back quickly, as a score of shots rang out.

What the youths saw was forty or fifty natives scattered out to escape the fire of the soldiers. Each held in readiness an old rifle, which he discharged at intervals.

“Must be a revolution,” observed Bob. “Perhaps those natives have offered violence to the governor of the town, and the troops have been called to settle the matter.”

Bob could not have come closer to the facts.

“The soldiers are winning,” said Joe. “They’re better trained and have more efficient guns.”

Although the troops appeared to gain the upper hand, the fighting continued with as much fury as before.

A sudden fusillade of bullets coming dangerously near Bob and Joe prompted the boys to make a dash toward the end of the town, where the mules and Dr. Rander were probably waiting.

“Let’s get out of here,” suggested Joe. “We’ll get hit if we don’t.”

“All right. Wonder if Dr. Rander is still where we left him?”

The chums were greatly surprised when, a few minutes later, they saw that the old man was not in sight. But the mules were tethered to a stout post, and this gave the boys hope.

“Chances are, he’s gone to see what the shooting’s about,” Bob said. “Wish he’d come back. He’s likely to get killed if he stays around there close.”

The youths were beginning to worry when Dr. Rander appeared up the road, glancing occasionally over his shoulder.

“Quite a commotion, wasn’t it?” he said when he had come nearer. “But the soldiers drove them away.”

“What was it, a revolution?” inquired Joe.

“Yes. An Indian told me that the people in the town were turning against their prefect. Didn’t like his rule, and wanted a change. But the soldiers soon fixed them.”

“Is the fighting over?” Bob had not heard a rifle shot for several minutes.

“Yes. The soldiers forced the citizens to throw away their weapons.”

“And that reminds me,” laughed Joe. “We’d better be getting our rifles out, because we may see some game before long. I’d like to get a shot at a condor.”

“Condors live only in high mountains,” explained Dr. Rander. “We won’t see any for many days, if at all.”

But although the adventurers did not catch a glimpse of these huge birds, they saw occasional small animals, such as rabbits and chinchillas. Once Joe took a shot at one of the latter creatures, but his aim was not steady and he missed.

At noon that day they came to a small adobe hut, from which hung a green wreath.

“What does that stand for?” asked Bob innocently. “Is somebody dead?”

For the second time since the youths had known him, old Dr. Rander burst out in laughter.

“Hardly,” he said finally. “A green wreath means that bread is for sale.”

Joe almost choked with laughter.

“That’s a good one on you,” he said to his chum. “It’s a wonder you didn’t go and gather flowers and offer them to the bereaved family.”

Bob grinned.

“You’d probably have asked where the corpse was,” he said. “Or maybe——”

“We can stop here for a meal,” Dr. Rander interrupted. “It is best to save our provisions as best we can, because later on we won’t be able to find any native huts.”

Inside the mud building, the three were waited upon by a huge Indian woman, whose hard face inspired no trust from the explorers. But they were glad when she spread before them a bountiful meal of potatoes, roast mutton, and a drink which the youths guessed was intoxicating.

“None of that brown liquid for me,” came from Bob, looking with suspicion at the huge clay cup that contained the beverage.

“Me either,” echoed Joe. “Too big of a risk.”

The old man, however, drank freely of the beverage and seemed pleased with its flavor. Whether he knew of its ingredients the chums did not know.

As soon as the meal was over, the three again took up the journey, keeping a sharp lookout for anything that might prove of interest.

They found something before they had gone another mile.

Coming up the trail at a slow, leisurely gait was a large donkey, on the back of which rode an Indian man, woman, and two half-grown children. But something else amused the chums more. In pouches secured to the mule’s sides were two other Indian children, their faces sober as they looked upon the whites.

“Where’s a movie camera?” demanded Bob quickly. “I’m going to take a chance with them. They can’t do anything to us.”

“Here.” Joe had removed a camera from his pocket and was turning the crank and exposing several yards of film. “This ought to be interesting on the screen,” he said.

Much to the youths’ surprise, the Indians did not protest at having their pictures taken. They merely stared at the whites in wonder.

“Maybe they haven’t seen a camera before, and don’t know what it’s all about,” was the opinion expressed by Joe.

A little later they came to a flat field, which was being cultivated by an Indian with a team of oxen and a crude wooden plow. It was an interesting sight. The slow animals drew the improvised instrument steadily through the hard soil, while the sober Indian watched closely.

“More movies,” sang Bob, bringing out his camera. “Every little bit counts.”

Again they were surprised to see that this Indian displayed no indignation at the whites taking pictures. Perhaps after all Joe was right and the Indians in this section were not familiar with a camera.

The adventurers had been driving their pack animals ahead all afternoon when suddenly they rounded a bend and came to a narrow river.

“Look!” cried Joe quickly, pointing ahead. “What’s that on the bank? Why, it’s bones!”

Dr. Rander had heard.

“Llama remains,” he explained. “Looks like llamas have picked this spot to die on.”

Scattered thickly over the river bank were scores of white bones, which undoubtedly were those of llamas.

“I knew elephants occasionally have a cemetery, but that any other animals do I had not the slightest idea,” said Joe.

More movies were taken, and then they set about to devise a means to cross the river.

“We’ll have to ford it,” announced Dr. Rander, who had been waiting for the chums to walk on up to the head. “I don’t think it is so deep as to cause us trouble.”

Although the weather was warm, Bob and Joe chose to put on their hip boots, to escape the chill that might otherwise result.

They found that Dr. Rander was right. The river was barely three feet deep and was comparatively calm. So they had little difficulty in driving the mules across.

From the opposite bank two trails branched off up the mountainside. The one that was most difficult to follow, Dr. Rander chose.

“From here our going will be more arduous,” he told the young men. “The mountains are steeper, and more obstacles will stand in our way.”

Bob had followed the pack train to a height where he could command a good view of the surrounding country when suddenly he cried out in pain.

“My foot!” he groaned, when the others rushed to his side. “Something bit it.”

“What was it? A snake?” Joe demanded anxiously.

“Let me have a look at it,” the old man said, tying the foremost mule to a gnarled tree.

When Bob removed his legging and sock, he found a large red scratch, and the flesh about it was already badly swollen. It pained severely and throbbed so violently that the boy could hardly hold his foot still.

“Not a snake,” Dr. Rander told him. “Rather a poisonous insect—they are common in the Andes.”

The old explorer bathed the foot in water from a canteen and treated it with antiseptics, wrapping it up firmly.

“Now until that heals some you’ll have to ride your mount,” Dr. Rander said. “Don’t take no from him for an answer. Get on him and make him carry you forward.”

While Joe and the old man held the mule securely, Bob mounted and with drawn reins held the animal at a standstill.

“Hurrah!” yelled Joe. “You’ve made him give in.”

“Not altogether,” Bob said. “But I think I can manage to stay on.”

At the end of two days of riding the mule, Bob was convinced that the animal was not really as balky as he had at first supposed. Over high hills and rocky paths he carried his rider, until at last Bob’s foot became well enough for him to walk.

“I’ll sort of hate to do it,” laughed the youth, when they were camped under a high overhanging rock.

“I know,” said Dr. Rander. “But there isn’t much choice in the matter. After all, our mounts are not to be ridden except in such an emergency as this. They tire too easily when on the rocky trails, and it isn’t best to put much of a load on them.”

On, on the little party plunged, into the heart of the mountainous region. On every hand they saw something to hold their interest.

They had been on the trail about four days when they saw something that was indeed unusual.

Moving leisurely up the narrow path were eight or ten large Indians carrying an old organ. Ropes were tied tightly around the instrument, and to these the Indians held with a death grip.

Where they were taking the organ, the whites could only guess. Perhaps it belonged to a plantation owner, who wanted a musical instrument in his house.

Suddenly, unexpectedly, one of the Indians cried out in fright, and then there came other cries.

“The organ’s slipping!” shouted Joe. “It’s going over the cliff! And oh!”—he gasped for breath—“it’s taking one of the Indians with it!”