"Over 17,000 feet high," was the sullen rejoinder.

"Well," the boy went on, "if that really is Vilcanota, we are still in the land of the living. In fact, we can't be more than twenty-five miles from a town, and there is a railroad--so my maps say--over to the east. It ends at Sicuani, and there the upper branch of the Uacayli river begins. This river empties into the Amazon at the head of steamboat navigation, the maps say."

"You seem to know a lot about this part of South America," gritted Collins.

"And over to the south," Ned went on, "is Lake t.i.ticaca, and over the mountains from that body of water is Coroico, where the Beni river starts on its long run to the Amazon, by way of the Madeira river."

"Well," snapped Collins, drawing hard at the strap which held his wrists, "you can't sit here and figure yourself out of this hole.

Why don't you do something?"

"Why, I thought it might be a good plan to wait until dawn," laughed Ned. "Then I may be able to repair this machine."

"Repair nothing!" stormed Collins. "And in the meantime, I presume you think you are going to keep me tied up like a calf going to market?"

"About that way," Ned responded, whereat the captive snorted out his rage and rolled over on his face and pretended to be asleep.

In a short time dawn shone on the tops of the tallest mountains, and directly it crept slowly down into the pit where the wrecked aeroplane lay. By this time Ned had mapped out a course of action.

The aeroplane he had seen in the night had descended not far from this spot, and he had decided to climb to some convenient height and look about for it. If he could come upon the Nelson, in good sailing condition, there would be no need of repairing the Vixen, or trying to do so.

Collins had counterfeited sleep until, utterly exhausted, he had actually dropped off into slumber, so Ned had no captive to watch for the time being. Before leaving for a tour of inspection he examined the broken planes and discovered that it would be impossible for him to repair them, at least without the necessary tools and materials.

Climbing to the level bit of sand, then, he faced the east and began the ascent of a mountain spur which seemed to reach the very heavens. It was a beautiful morning, the air being sharp and clear at that height. Ned felt that he could have enjoyed the beauties of nature more fully, however, if he had something in the way of breakfast!

He climbed steadily for an hour, and then came to a narrow ledge which seemed to surround one of the lower peaks of the mountain.

Pa.s.sing around to the south, he heard a shout, then a fall--a b.u.mping fall which told of a body bouncing from one rocky level to another.

He ran around the angle ahead of him and came out on a shelf-like elevation from which a green little valley, half way up the side of the mountain, might be seen. In the center of the valley, carefully blocked against sudden motion, lay the Nelson.

Ned could have danced with delight. The aeroplane appeared to be in perfect condition, but there was no one insight. Jimmie and Pedro must be about somewhere, the boy thought, as he considered the most practical way of reaching the valley, but where were they?

He was about to call out in the hope of arousing one of the aviators to action when he saw a hand waving at him from underneath the gray planes. A more careful inspection of the spot revealed the dirty face of little Jimmie, who was lying on his face, an automatic in each hand. Pedro was nowhere to be seen.

Ned watched the signaling hand for an instant and then, in response to what it said to him, scudded around the angle of rock by which he had reached the shelf. As he did so an arrow whizzed past his right ear and blunted against the rocky wall.

The situation was not difficult to understand. Jimmie had dropped the Nelson into the little valley and had there been attacked, either by savages or those interested in the defeat of the Boy Scout expedition to Paraguay, though how the latter could have reached that lonely spot so soon after the landing of the aeroplane was a mystery which the boy could not fathom.

Following the attack, Jimmie had hidden under the planes, and Pedro had probably taken to his heels. The situation explained, doubtless, why the boy had not returned with the airship. He had been held there by the enemies, virtually a prisoner.

After a short pause, during which Ned listened intently for some sound of pursuit, the boy moved cautiously to the shoulder of rock and looked around it to the shelf. There was no one in sight, so he pressed on, and once more came within view of the aeroplane.

Back of the planes he saw a head lifted from the lip of a gully which cut the valley like a trench. It was not the head of a savage, nor yet the head of a Peruvian mountaineer, for it was covered down to the eyebrows by a flat-topped leather automobile cap which was adorned with driving goggles! Evidently an American!

While Ned, himself unseen, watched the cap and the goggles, the wearer lifted himself and looked up over the edge of the gully. He wore a gray suit, tailor-made, from all appearances.

Back of him three ill-visaged Peruvian Indians also raised themselves to get a view of what was doing in front.

So the savages were led by an American! Instead of the automatic of civilized warfare, the enemy was resorting to the poisoned arrow of the barbarian!

An American there and in automobile costume! Where was the machine, and how in the name of all that was wonderful had it been brought to that rough country?

And why were the enemies crouching there, when their only opponent was a boy, hidden if his position may be so termed--under the planes of an airship--planes which would offer little resistance to an arrow or a bullet?

But while the boy looked and wondered a shot came from the very shelf on which he stood, and one of the exposed Indians dropped in his tracks. Then the situation became a bit clearer.

Pedro had escaped from the valley to the shelf of rock, and was standing guard there shooting whenever the attacking party attempted to reach the aeroplane.

In a moment the automobile cap and goggle and the evil faces of the Indians disappeared from view. The attacking party had dropped back into the gully, which was some distance from the machine.

Waiting a moment, in order to make sure that no one was stirring behind the shoulder of rock, Ned called softly:

"Pedro!"

"h.e.l.lo!" came the answer back.

"'Where are you?" asked Ned, recognizing the voice of the Peruvian he had talked with at Lima.

"In a notch of the rock," came the answer, in Spanish.

Ned moved along the shelf, and soon came to where Pedro stood, sheltered by a jutting ledge. The journey was not accomplished without attracting the attention of the others, for an arrow whizzed past his head as he crept into the angle with Pedro.

Pedro expressed great joy at the arrival of the boy, and explained that the situation as then shown had existed since dawn. On the afternoon of the previous day Jimmie, being then about to return to Lima, had found it necessary to land in order to repair a slight break in a plane.

The driver of the pursuing Vixen, noting the temporary disablement, had circled around the valley for a short time and then returned to Lima. It was Pedro's idea that the Vixen would not return with a.s.sistance, but with enemies who would destroy the machine, leaving Jimmie and himself to find their way out of the mountains as best they could.

Jimmie, Pedro said, had been unable to fix the Nelson for flight until about daylight, and then the attacking party had appeared.

Since then it had been impossible to get the machine into the air, as every motion at the airship brought a bullet or a poisoned arrow.

Just before Ned's arrival, an Indian had, by making a long journey around the cliff, gained the shelf of rock where Pedro was stationed, and been caught unawares and thrown down into the valley.

It was the cry and the fall of this foe that Ned had heard.

"But," Ned said, "the Vixen must have summoned some one active in the conspiracy before returning to Lima, for the man over there came in an automobile, and did not come very far either. He certainly did not come from Lima, which is more than three hundred miles away."

"He might have come from Sicuani," replied Pedro. "That is over to the east, and not more than twenty miles off. I have heard that there is a path by means of which a motor car can reach this place.

Yes, he must have gone to Sicuani, otherwise this man of the motor car would not be here," Pedro added.

This cleared the situation not a little, and Ned was now encouraged to make an attempt to reach the Nelson, which Pedro declared to be in good condition for flight. If the others had come in an automobile, there could not be many of them. Probably not more than six in all, and two had been wounded, or killed.

Pedro insisted that, with Ned guarding him from the shelf, he could reach the machine, but the boy thought it wiser to make the desperate journey himself. Even if the Indian reached the Nelson, the two of them might not be able to get the machine into the air, as Jimmie had had little experience in running a plane.

So, after explaining to Pedro that he would be taken up later, Ned began the task of making his way down the almost perpendicular face of the cliff. Much to his surprise, there were no hostile demonstrations from the gully in which the attackers had disappeared a short time before.

Instead of shots and the whiz of arrows, the boy heard, when half way down the slope, the distant whirr of a motor car!

"There is some trick in the wind," Ned thought. "They would never run away in that manner because of the wounding of two Indians and the arrival of one boy from the outside."

It was deathly still in the valley where the aeroplane lay. Sounds from a distance came with remarkable distinctness, so the popping of the motors of the automobile were plainly heard, and the direction taken by the machine was thus made known.