"I believe you're right," cried Walt Phelps; "and that other pony beyond, is the dead spit of Firewater, Jack Merrill's favorite mount."

"And, if I mistake not, that large, bony animal yonder, regarding me with a suspicious optic, is the equine I bestrode at the time we were captured," exclaimed the professor, who had been looking eagerly about him.

"Boys, this is a wonderful discovery," he went on. "I have read of these sunken valleys, but have never seen one before; I should like to examine the geological formation hereabouts."

"Some other time," laughed Ralph; "what I wonder at is that the Mexicans never discovered the secret passage."

"That's not surprising," chimed in Walt Phelps, "the mouth of it is all screened with thick brush, and unless you fairly fell into it you would never know it was there."

"That is so," agreed the professor, "but now, boys, that we are once more in the blessed air, what are we to do?"

"My advice would be to press on till we can find some village. Once there, we shall be safe, and can find some soldiers, or, at least, summon them from wherever their garrison may be. It is our duty to Jack Merrill and Coyote Pete to use every means in our power to save them," said the professor, who, of course was, like his companions, ignorant of the fact that at that very minute the two he spoke of were riding over the distant foothills for their lives.

This also explained why the party that had just emerged from the tunnel were not molested. Every man that could be spared from immediate guard duty had been summoned to help form the great human circle, which, as we know, Ramon had attempted to spread about Jack Merrill and the sagacious cow-puncher.

"There doesn't seem to be anybody about," said Walt, after a short silence, "let's get in the shadow of the rock wall and creep forward."

"Better yet, if we only had some rope," suggested Ralph.