For a moment the young inventor felt a cold chill run down his spine, and, while his hair did not actually "stand up" there was a queer sensation on his scalp as if the hairs wanted to stand on end, but couldn't quite manage it.

Involuntarily Tom started, and one of the sticks he held in his hand dropped to the ground. The green eyes shifted--they came nearer, and the lad heard a menacing growl. Then he knew it was some wild animal that had dropped down from a tree and was now confronting him, ready to spring on the instant.

Tom hardly knew what to do. He realized that if he moved it might precipitate an attack on him, and he found himself dimly wondering, as he stood there, what sort of an animal it was.

He had about come to the conclusion that it was something between a cougar and a mountain lion, and the next thought that came to him was a wonder whether any one else in the camp was awake, and would come to his rescue.

He half turned his head to look, when again there came that menacing growl, and the animal came a step nearer. Evidently every movement Tom made aroused the beast's antagonism, and made him more eager to come to the attack.

"I've got to keep my eyes on him," mused the lad. "I wonder if there's any truth in the old stories that you can subdue a wild beast with your eyes--by glaring at him. But whether that's so or not, I've got to do it--keep looking him in the face, for that's all I can do."

True, Tom held in his hand some light sticks, but if it came to a fight they would be useless. His gun was back in the tent, and as far as he could learn by listening there was not another soul in the camp awake.

Suddenly the fire, which had almost died out, flared up, as a dying blaze sometimes will, and in the bright glare the young inventor was able to see what sort of beast confronted him. He saw the tawny, yellow body, the twitching tail, the glaring eyes and the cruel teeth all too plainly, and he made up his mind that it was some species of the cougar family. Then the embers flared out and it was darker than before. But it was not so dark but what Tom could still see the glaring eyes.

"I've got to get away from him--scare him--or shoot him," the lad decided on the instant. "I'd like to bowl him over with a bullet, but how can I get my gun?"

He thought rapidly. The gun was in the tent back of him, near where he had been sleeping. It was fully loaded.

"I've got to get it," reflected Tom, and then he dropped the other sticks in his hand. Once more the beast growled and came a step nearer--soft, stealthy steps they were, too, making no sound on the ground.

Then Tom started to make a cautious retreat backwards, the while keeping his eyes focused on those of the beast. He made up his mind that he would give that "hypnotism" theory a trial, at any rate.

But at his first backward step the beast let out such a fierce growl, and came on with such a menacing leap that Tom stood still in very terror. The animal was now so close to him that a short jump would hurl the beast upon the lad.

"This won't do," thought Tom. "Every time I go back one step he comes on two, and it won't take him long to catch up to me. And then, too, he'll be in the tent in another minute, clawing Ned or Mr. Damon. What can I do? Oh, for a gun!"

He stood still, and this seemed to suit the animal, for it remained quiet. But it never took its eyes off Tom, and the switching tail, and the low growls now and then, plainly indicated that the beast was but waiting its time to leap and give the death blow.

Then an idea came to Tom. He remembered that he had once read that the human voice had a wonderful effect on wild animals. He would try it.

"And I'm not going to sing him any slumber song, either," mused Tom. "I'll start on a low tone to call for Ned, and gradually raise my voice until I wake him up. Then I'll tell Ned to draw a bead on the beast and plunk him while I hold his attention."

Tom lost no time in putting his plan into operation.

"Ned! Ned! Say, old man, wake up! I'm in trouble! There's a beast as big as a lion out here. Ned! Ned! Ned!"

Tom began in a low voice, but increased his tones with each word. At first the beast seemed uneasy, and then it stepped switching its tail and just glared at Tom.

"Ned! I say Ned! Wake up!"

Tom listened. All was silent within the tent.

"Ned! Oh, Ned!"

Louder this time, but still silence.

"Hey, Ned! Are you ever going to wake up! Get your gun! Your gun! Shoot this beast! Ned! Ned!"

Tom waited. It seemed as if the beast was nearer to him. He called once more.

"Ned! Ned!" He was fairly shouting now. Surely some one must hear him.

"What's that? What's the matter? Tom? Where are you?"

It was Ned's voice--a sleepy voice--and it came from the interior of the tent.

"Here!" called Tom. "Out in front--by the fire--get your gun, and get him with the first shot, or it's all up with yours truly."

"Get who with the first shot. Who are you talking about?"

"This cougar! Hurry Ned, he's creeping nearer!"

Tom heard a movement behind him. He dared not turn his head, but he knew it was his chum. Then he heard a gasp and he knew that Ned had seen the beast. Then all Tom could do was to wait. And it was not easy waiting. At any moment the beast might spring, and, as far as he was concerned it would be all over.

Nearer and nearer crept the brute. Again Tom felt that queer sensation down his spine.

"Hurry, Ned," he whispered.

"All right," came back the reassuring answer.

There was a moment of silence.

Crack! A sliver of flame cut the darkness. There was a report that sounded like a cannon, and it was followed by an unearthly scream. Instinctively Tom leaped back as he saw the greenish eyes change color.

The young inventor felt a shower of dirt thrown over him by the claws of the dying cougar, and then he realized that he was safe. He raced toward the tent, to be met by Ned, and the next instant the camp was in wild commotion.

"Bless my slippers!" cried Mr. Damon. "What has happened. Tell me at once?"

"Fo' de lob of chicken!" yelled Eradicate from a tent he had all to himself--the cook tent.

"Santa Maria! Ten thousand confusions! What is it?" fairly screamed Delazes.

"Are you all right, Tom?" called Ned.

"Sure. It was a good shot."

And then came explanations. Wood was thrown on the fire, and as the Mexicans gathered around the blaze they saw, twitching in the death throes, a big cougar, or some animal allied to it. Neither Tom nor his friends had ever seen one just like it, and the Mexican name for it meant nothing to them. But it was dead, and Tom was saved and the way he grasped Ned's hand showed how grateful he was, even if he did not say much.

Soon the excitement died out, after Tom had related his experience, and though it was some time before he and the others got to sleep again, they did finally, and the camp was once more quiet.

An early start was made the next day, for Tom had reconsidered his determination to assemble the balloon and explore in that air craft, And the reason for his reconsideration was this:

They had not gone far on their journey before they met a solitary Mexican, and of him they asked the usual question about the plain of the temple.

He knew nothing, as might have been expected, but he stated that there was a large village not far distant in which dwelt many old Mexicans.

"They might know something," he said.

"It's worth trying," decided Tom. "I'll wait until to-morrow about the balloon. We can make the village by noon, I guess. Perhaps we can get a clew there."

But it was nearly night when the ox carts drew into the Mexican settlement, for there was an accident in the afternoon, one of the vehicles breaking down.

There were fires blazing in many places in the village, which was one of the most primitive sort, when our friends entered. They were curiously watched as they drove through on their way to a good camping site beyond.

And here, once more, fate stepped in to aid Tom in his search for the city of gold.

As they were out of corn meal, and needed some for supper, Tom told Eradicate to stop at one of the larger houses to buy some. The lad followed the colored man into the building, which seemed to be used by several families.

"We'll be obliged to yo' all fo' some corn meal," began Eradicate, picking out an aged Mexican to whom he addressed his request.

"What is it?" asked the Mexican in Spanish.

Tom put the question in that language, and he was on the point of explaining that they were travelers, when he stopped midway, and stared at something on a rude shelf in the main room of the house.

"Look! Look, Ned!" whispered Tom.

"What is it?" asked his chum.

"On that shelf! That image! The image of gold! One just like the drawing Mr. Illingway sent from Africa! Ned, we're on the trail at last, for there is one of the small images from the city of gold!" and Tom, with a hand that trembled in spite of himself, pointed at the small, yellow figure.