ion, they might have passed it unnoticed.

A brief inspection showed that it was a small cave, about twenty feet
in depth, and, as has been said, well screened from below.

"We're not likely to find a better place," announced Jack, after a
hasty inspection.

"Turn the horses loose," he cried in a low, but penetrating voice, down
to Walt, who had remained below with the stock.

The red-headed ranch boy slipped off the back of his steed and alighted
on a rock, so as to make no tracks. He then gave the three horses,
that had borne them so bravely, their liberty. At first the animals
would not move, but began cropping the green stuff about them.

"Here, that won't do," breathed Jack, as the three lads crouched at the
cave mouth. "Throw some rocks at them, Walt."

The boys picked up some small stones, which lay littered in front of
the cave, and commenced a fusillade. It had such good results, that a
few seconds later, the three horses were plunging off along the bottom
of the gully as if Old Nick himself had been after them.

As their hoof-beats grew faint, Jack held up his hand to enjoin
silence, although the boys had been discussing their situation in such
low tones that their voices could not have traveled ten feet from the
cave mouth.

"Hark!" he said.

From farther down the gully came shouts and yells, and then the
distinct rattling sound of loose shale, as several horsemen descended
the steep bank into the gulch.

"They've picked up the trail," commented Walt grimly.

CHAPTER XVI.

WHAT HAPPENED TO COYOTE PETE.

Let us now retrace our steps to the Haunted Mesa, and ascertain how it
fared with Coyote Pete and the professor, after the boys' astonishing
disappearance through the balanced trap-door in the base of the hollow
altar. As we know, the lads' elders were crouched at the opposite end
of the former sacrificial structure, when, before their eyes, the lads
were swallowed up.

For an instant--as well they might have been--the two onlookers were
fairly paralyzed with amazement. The occurrence seemed to be without
natural explanation. But an investigation by Pete, crawling on his
hands and knees while he made it, soon revealed the nature of the
device which, as we know, was nothing more nor less than a balanced
trap-door of stone. An unusual weight placed upon one end of it
instantly tilted it and projected whatever was on it upon the staircase
below.

The professor, who recalled havin