One day, after a night camp on the edge of a rather high table land, they started across a fertile plain that was covered with a rich growth of grass.

“Good grazing ground here,” commented Ned.

“Yes,” put in San Pedro.  “Plenty much horse here pretty soon.”

“Do the natives graze their herds of horses here?” asked Tom.

“No natives—­wild horses,” explained Pedro.  “Plenty much, sometimes too many they come.  You see, maybe.”

It was nearly noon, and Tom was considering stopping for dinner if they could come to a good watering place, when Ned, who had ridden slightly in advance, came galloping back as fast as his steed would carry him.

“Look out!  Look out!” he cried.  “There’s a stampede of ’em, and they’re headed right this way!”

“Stampede of what?  Who’s headed this way?” cried Tom.  “A lot of monkeys?”

“No, wild horses!  Thousands of ’em!  Hear ’em coming?”

In the silence that followed Ned’s warning there could be heard a dull, roaring, thundering sound, and the earth seemed to tremble.

“The young senor speaks truth!  Wild horses are coming!” cried San Pedro.  “Get ready, senors!  Have your weapons at hand, and perchance we can turn the stampede aside.”

“The rifles!  The electric rifles, Ned—­Mr. Damon!  We’ve got to stop them, or they’ll trample us to death!” cried Tom.

As he spoke the thundering became louder, and then, looking across the grassy plain, all saw a large troop of wild horses, with flying manes and tails, headed directly toward them!

CHAPTER XI

CAUGHT IN A LIVING ROPE

“Quick!  Peg out the mules!” cried San Pedro, after one look at the onrushing horses.  “Drive the stakes well down!  Tie them fast and then get behind those rocks!  Lively!”

He cried his orders to the natives in Spanish, at the same time motioning to Tom and Ned.

“Get off your mules!” he went on.  “Peg them out.  Peg out the others, and then run for it!”

“Run for it?” repeated Tom, “Do you think I’m going to leave my outfit in the midst of that stampede?” and he waved his hand toward the thundering, galloping wild horses which were coming nearer every moment.  “Get out the electric rifles, and we’ll turn that stampede.  I’m not going to run.”

“Bless my saddle!” cried Mr. Damon.  “This is awful!  There must be a thousand of them.”

“Nearer two!” cried Ned, who was struggling to loosen the straps that bound his electric rifle to the side of his mule.  Already the pack animals as well as those ridden by the members of the giant-hunting party were showing signs of excitement.  They seemed to want to join the stampeding horses.

“Peg our animals out!  Peg them out!  Make them so they can’t join the others!” yelled San Pedro.  “It’s our only chance!”

“I believe he’s right!” cried Mr. Damon.  “Tom, if we wait until those maddened brutes are up to us they’ll fairly sweep ours along with them, and there’s no telling where we’ll end up.  I think we’d better follow his advice and tie our mules as strongly as we can.  Then we can go over there by the rocks, and fire at the wild horses.  We may be able to turn them aside.”