The boys were in no doubt as to the author of this startling break in the mountain stillness. It was their own burro that had given out the unearthly roar, and they were confident of being close upon the trail of the two men who were making off with the gold. But a moment later, round the corner in front of them, the donkey's head came into view, his long ears flapping, as if training themselves for the fight with mosquitoes that would soon come. The animal was walking slowly, but the astonishing fact immediately appeared that he was not only without any load on his back, but was unaccompanied by either Hardman or his confederate.

Suspecting, however, they were close behind him, the boys held their places, the foremost still on the alert for the criminals. The burro came forward until within a rod, when he seemed to become aware for the first time of the presence of the youths in his path. He halted, twiddled his rabbit-like ears, looked at the two, and then opened his mouth. The flexible lips fluttered and vibrated with a second tremendous bray, which rolled back and forth among the mountains, the wheezing addendum more penetrating than the first part of the outburst.

As the animal showed a disposition to continue his advance, the boys stepped aside and he came slowly forward, as if in doubt whether he was doing a prudent thing; but he kept on, and, passing both, continued down the trail, evidently anxious to return to his pasturage.

"What does it mean?" asked Roswell.

"I have no idea, unless—"

"What?"

"They can't make any further use of the burro, and have allowed him to go home."

"But they can't carry away all the gold."

"Then they are burying it. Let's hurry on, or we shall be too late."

Lowering his Winchester, Frank led the way up the trail, slackening his pace as he reached the bend, and partly raising his weapon again.

Rocks and bowlders were all around, but the trail still showed, and the donkey could have travelled indefinitely forward, so far as the boys could see. Nowhere was anything detected of the two men.

"They may have turned the burro loose a half mile off," said Frank, chagrined and disappointed beyond expression.

His companion warned him to be careful, as he began pushing forward at a reckless rate, as if fearful that the men would get away after all.

Just beyond the point where the burro had appeared the path forked, each course being equally distinct. The boys scrutinized the ground, but could not decide from what direction the animal had come. Had they possessed the patience, they might have settled the question by kneeling down and making their scrutiny more minute; but Frank could not wait.

"I'll take the right," he said, "while you follow the left. If you discover either of them, shoot and shout for me."

It may be doubted whether this was wise counsel, and Roswell did not feel himself bound by it, but he acted at once upon the suggestion. His weapon was in his grasp as he hurried over the path, and the cousins were quickly lost to each other.

The inspiring incentive to both boys was the dread that they were too late to recover the gold that had been stolen. Since its weight was too great for a couple of men to carry, the natural presumption was that they had buried or would bury it in some secure place, and return when it was safe to take it away.

Because of this, Roswell Palmer sharply scrutinized every part of his field of vision as it opened before him. There were nume............