ed. Tad Butler saw this and so did the
Professor, but neither mentioned the fact. Their location was no
longer dry. The spray from the waterfall had drenched them to the
skin. No one complained. They were too used to hardships.

All at once there came a report louder and different from the others,
followed by a crashing, a thundering, a quaking of the rocks beneath
their feet, that sent the blood from the face of every man in the
party. Even Dad's face grayed ever so little.

The next second each one was thrown violently to the ground. A sound
was in their ears as if the universe had blown up.

"We're killed!" howled Chunky.

"Help, help!" yelled Walter Perkins.

"What---what is it?" roared the Professor.

"We're struck!" shouted Tad.

"Lie still. Hug the wall!" bellowed the stentorian voice of Jim Nance,
who himself had crept closer to the Canyon wall and lay hugging it
tightly.

The deafening, terrifying reports continued. One corner of the ledge
over their heads split off, sending a volley of stones showering over
them, leaving the faces of some of the party flecked with blood where
the jagged particles had cut into their flesh.

It was a terrible moment for the Pony Rider Boys.

CHAPTER X

ESCAPE IS WHOLLY CUT OFF

Not one could collect his thoughts sufficiently to reason out what had
taken place. The guide, however, had known from the first. He feared
that his charges would be killed, but there was nothing more that he
could do.

The bombarding continued, some explosions sounding near at hand, others
further down or up the Canyon, but each of sufficient force to send
shivers up and down the spines of the Pony Rider Boys. They never had
experienced anything approaching this.

"I'm going to stand up," declared Tad, rising to his feet. "I won't
be killed any quicker standing than lying down. Besides, I don't like
to shirk."

"Stand up if you want to, but keep close to the wall," ordered Dad,
himself rising to his feet.

One by one the boys got up, Professor Zepplin following the example of
the guide. They had to shout in speaking in order to make themselves
heard above the bombardment, the roaring of the river and the cataract
over their heads.

"What is going on up there?" shouted Tad.

"Mountain falling in!"

"I knew it! I knew it!" yelled Chunky. "I knew something would fall
down as soon as I got here."

No one laughed. The situation was too serious for laughter.