stillness broken only by the occasional wild scream of the ape, or the hoarse breathing of the boy as he fought to free himself from that horrible grasp.

The struggle must have lasted for two or three minutes—to Billie it seemed hours—when by a sudden wrench the lad managed to free his left arm sufficiently to get the beast by the throat. For an instant it loosed its hold on his right arm and that act decided the battle.

Finding his right arm free, Billie seized his revolver and without drawing it from the holster pulled the trigger.

At the sound of the shot, the ape uttered a plaintive cry, relaxed its hold upon the lad and fell upon its knees on the ground with its hands raised in supplication as previously.

"I ought to shoot you," declared the lad between his gasps for breath as he drew the weapon from its holster and pointed it at the animal, "but I won't. I'll take you with me and maybe I can sell you for enough to pay me for the scare you've given me. Now, march!"

He pointed with his finger down the track, but the beast would not stir.

"Don't you intend to do what I tell you?"

The animal perked up his head and kept his eye upon the revolver.

"Well," exclaimed Billie as he drew a long breath, "this is the limit. I can't make you mind and I won't hurt you. I guess the only thing I can do is to go and leave you."

Suiting the action to the word, Billie turned and started down the track, his revolver still in his hand.

He had not gone more than a dozen steps, before he heard the soft pat-pat behind him, and on looking back could see nothing but the waving grass to indicate the whereabouts of his erstwhile assailant.

"So I am to be followed, am I? Well, all right." Then, as an afterthought: "I wonder how I can catch him when I want him. I wonder if this will do," and he raised his weapon and pointed it toward the moving grass.

With the same plaintive cry which Billie had come to recognize as one of fear, the animal ran toward him and sank to his knees.

Billie smiled.

"It's all right, old chap. As long as I know how to handle you, why you can follow me right back to the train."

Again he started down the track at a brisk walk, it having just occurred to him that there might be something doing at the other end of his journey.

Twenty minutes later he reached the station at Pitahaya where he had expected to find Adrian and the three Mexicans awaiting him, but, as we know, they had gone on to the scene of the wreck. Not realizing just what had happened, but always on the alert for the unexpected, Billie, therefore, began an inspection of the station.

It did not take him long to discover that Pitahaya was little more than a siding with a one-room building, which was used as a freight house and a waiting room. It did not even boast of a station master.

"There must be some reason for having a building here," he mused. "There must be some sort of a settlement around somewhere. But what's that to me? I might as well be jogging along towards Pachuca."

Then he bethought him of the ape, which he had no mind to lose after his exciting experience. But the animal was nowhere to be seen.

"I wonder if I could raise him with a shot," soliloquized Billie.

He raised his weapon, which he still carried in his hand, and fired aimlessly, while he turned his eyes in various directions, but there was nothing to be seen.

"Oh, well," he thought, "what's the difference? He'd just be a nuisance anyway. I might as well be trudging along."

He jumped off the station platform and proceeded down the track, filling the magazine to his automatic as he went. Then having finished the task, he returned it to his holster and once more began counting the ties.

"One, two, three, four, five, six——"

Bing! And a stone whistled by his head.

Billie turned, and as he did so a second stone from the same source struck him on the temple, and he fell to the ground.

A second later the ape sprang from a palm beside the station and ran toward him, stopping every few feet to see if the lad would rise.

When within a few feet of the prostrate lad the animal made a leap and landed upon his body. In another instant it had gained possession of Billie's weapon, which it examined curiously for a moment, ere it sprang away and stationed itself some two rods distant, where it sat watching with the weapon aimed directly at him.

For perhaps five minutes the two retained their relative positions and then Billie began to regain consciousness. Several times he moved uneasily and then he suddenly sat up and looked around.

"I wonder what happened," he finally thought, and then he became conscious of a pain in his head.

He raised his hand to the aching spot and his fingers encountered a big lump.

The truth came upon him like a flash. He dropped his hand to his holster, and sprang to his feet.

As he did so he caught sight of the ape and found himself looking into the business end of his own weapon.

With a yell he dropped to the ground as though the expected had happened.

But when no shot followed, he began to regain his wits and lay still trying to figure out once more just how much the ape might know about the use of the weapon.

He remembered the old saying that a gun was a dangerous weapon without lock, stock or barrel, because a man killed his wife with the ramrod; and so he figured that an animal which had intelligence enough to throw a stone and knock him senseless, might have sense enough to fire a revolver.

"If I only knew something about his history," soliloquized Billie, "I might be able to guess how much he knew. But he is a perfect stranger to me. I don't even know his name."

After several minutes and nothing had happened, Billie decided to make some effort to get away.

"I might as well be shot as to be prisoner to an ape," he thought, and so he arose to a sitting posture and surveyed the scene.

There sat the ape as before, with the automatic pointed at Billie, but with a puzzled look upon its face. When the lad finally arose, the ape appeared still more puzzled and at length, turning the weapon away from Billie, looked into the muzzle.

"That settles it," exclaimed Billie. "He doesn't know how to fire it. I'll go and take it away from him."

He started toward the animal, which at once pointed the revolver in Billie's direction. There came a sharp report and a bullet whizzed by the boy's head.

"Worse and more of it," exclaimed Billie. "He doesn't know how to use the thing, but he's liable to shoot me as long as I stay in range. I'll just make myself scarce."

Stooping down, he picked up a good-sized stone and hurled it at the ape and then, without waiting to see the result of his throw, jumped into the jungle which lined both sides of the track, determined to make a detour and if possible lose his unpleasant companion.

He had not run far before he realized that the ape was following, but this he did not mind. There were plenty of trees between them, and he felt sure he would soon be able to reach some sort of a habitation, when he suddenly found himself on the edge of a deep basin into which he plunged before he was able to gain his equilibrium.

CHAPTER IV.

THE ROSARIO VIEJO.

To be suddenly pitched head-foremost down a rocky declivity into a mass of prickly pear bushes and other tropical brambles is by no means pleasant; and as a result Billie was not in the best of humor when he picked himself up and looked to the top of the