"Never mind the bar," cried Adrian as he saw that Billie was raising the implement to throw it onto the platform. "Jump aboard!"

Billie started to obey, but the advice came too late. As he dropped the bar it struck one end of a tie, flopped over and hit him on the shin.

"Wow!" he yelled, grabbing his ankle with both hands.

"Never mind your leg," shouted Adrian. "Jump on or you'll be left."

Billie tried to obey, but the car was now under headway and although he sprinted his best, he was soon left behind.

Adrian started to jump off the car, but seeing his intention Billie called to him not to do it.

"I'll get there some time," he called. "Just tell them I'm coming," and he stood in the middle of the track looking ruefully after the rapidly disappearing car.

After some moments he picked up the claw-bar and threw it spitefully into the ditch beside the track, as much as to say, "Lay there! You're the cause of all the trouble." Then he started slowly after the car.

In the meantime Adrian was flying as fast back toward Pachuca as he had been flying away from it only a few minutes before. It could not have been more than ten minutes altogether since the wreck of the engine and Adrian figured that if the grade were steep enough the car might gain momentum enough to carry it back to the scene of the trouble; but he had little hope that it would.

When he shot through Pitahaya on his return trip, however, he saw that the car was going at a terrific rate of speed.

"What do you think?" he asked one of the Mexicans. "Do you think we'll get all the way back?"

"Cierto," was the reply. "When they first built this road they used to have mules haul the car to the top of this hill and then turn it loose and it would run almost to Pachuca. That was before it had any engines."

Adrian looked at the man and winked one eye very slowly.

"Senor, it is true," spoke up another. "I was a guard at the time."

Adrian could scarcely believe the statement, but he afterward learned that the men spoke the truth.

"Well, then," he said, "we had better look to our arms, for we may need them. There is no knowing how this affair has turned out."

The advice was well taken, for as they drew near the scene of the wreck, they saw that they were badly needed. More than a dozen hors.e.m.e.n were in sight at some distance from the wreck and with their long-range rifles were doing their best to pick off any one who showed his head.

"Our party must be out of ammunition," suggested Adrian, "or they would give a better account of themselves."

"Our carbines would not carry that far," explained one of the guards.

"Our Marlins will," replied Adrian, and as he spoke there were two simultaneous flashes from two of the car windows and two of the bandits fell, one shot from his horse and the other with his horse shot under him.

For a moment the other hors.e.m.e.n hesitated as to the course they should pursue and then, putting spurs to their horses, they dashed toward the train, just as the express car, having reached the end of the track, b.u.mped onto the ties and came to a stop.

"Now!" cried Adrian as the riders drew near, firing as they came, and four shots rang out.

The volley from so unexpected a quarter took the hors.e.m.e.n completely by surprise, and they pulled up with a jerk. The action proved their undoing, for as they stood thus for a moment, they gave those in the train the opportunity they desired and the volley that followed turned four more riderless horses upon the plain.

It was more than flesh and blood could stand, and the seven or eight remaining hors.e.m.e.n turned and fled, followed by at least three whistling bullets from as many Marlins.

The fight was over and the bullion had been saved, but what of Broncho Billie, who had been left at the top of the hill four miles away?

That was the first question asked by Donald when he greeted Adrian two minutes later.

"Oh, he's all right," was the laughing reply. "He's just taking a little walk for his health."

But when Billie failed to put in an appearance an hour later, the boys mounted their horses and started up the track to meet him, leading Billie's mount between them.

CHAPTER III.

BILLIE LOSES HIS NERVE.

Broncho Billie was not a rapid walker. In fact, if there was any one thing in which Billie was not a success, it was walking. He could ride a horse all day, but when it came to depending upon his own legs as a means of locomotion, he was a dead failure.

Therefore he walked slowly along, counting the ties as he went.

"They certainly do lay 'em thick," he mused after some minutes.

"Three hundred and one, three hundred and two, three hundred and three, three hundred and four, three hun----"

He stopped short and looked behind him.

"I sure thought I heard some one," he muttered. "It must have been a bird."

He turned and started forward.

"Let's see, where was I? Oh, yes, three hundred and five, three hundred and six, three hundred and----"

Again he stopped, but did not turn around. Instead he stooped down as though to pick up a stone, which enabled him to look backward between his knees.

He caught a movement in the gra.s.s at the edge of the right of way.

"I thought so," he muttered. "Now to find out who it is, and what he wants."

He picked up a small stone and threw it at a tall cactus which grew near the track some distance ahead.

"Good shot," he said aloud as the stone hit the stalk. "I wonder if I could do it again."

He stooped down and picked up another stone, taking a good look backward from his stooping position. There was not a movement to indicate the presence of a living thing.

"This is getting on my nerves," the boy mused as he picked up several small stones and again walked forward. "I don't mind being followed by a white man, but I'm a whole lot leary of these greasers. They're bad enough when they're friendly."

Then aloud, as he threw a couple of stones: "I'll never get anywhere if I don't make better time than this. I'll just sprint a few."

Suiting the action to the word, he started on a run.

Almost immediately he was aware of a soft pat-pat in his rear. He had heard a similar sound in the wilds of Wyoming and he recognized it at once.