"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.

"Is it a land or a rock slide?" questioned Tad further.

"Both," shouted Nance. "Mostly boulders."

The rain has loosened them and they are raining down on us. We're lucky we had this shelf to get under."

"From the present outlook I am afraid the shelf isn't going to protect us much longer," said Tad.

"Keep close to the wall and you will be all right. It won't break off short up to the wall. I've seen rock slides, but never anything quite like this. You see, the spirit of the Canyon was right," nodded Nance.

"Spirits? What spirits?" demanded Chunky. "Is this place haunted?

Don't tell me it is. Haven't I got enough to worry me already without being chased by ghosts?

"Chased by goats?" shouted the Professor.

"Who said anything about goats?" retorted Stacy. "I said g-h-o-s-t-s, spooks, spookees or spookors or whatever you've a mind to call them."

"Oh, I hope you are not losing your mind, Stacy."

"Might as well lose my mind as to lose my life. Mind wouldn't be any use to me after I was dead, would it?"

"The storm is dying out," called Ned.

Tad started to step from under the shelf, Nance grasped and hauled him back. Just then a great boulder, weighing many tons, struck the rock just above their heads, then bounded off into the river, which it struck with a mighty splash. The contact with the rocks sent off a shower of sparks, a perfect rain of them.

"I---I guess I need a guardian," said the lad rather weakly.

"Yes, you probably would have been killed by the smaller pieces that broke off," answered Nance. "Be content to stay where you are."

"How long have we got to stay cooped up in this half cave?" demanded Stacy.

"All night, maybe," answered Dad.

"Good night!" said the fat boy, Slipping down until he had a.s.sumed a sitting posture. He lay down and was asleep in a short time. Stacy woke with a start when another giant rock smote the wall just above their cave, exploding into thousands of pieces from the violent contact.

"Stop that noise! How do you suppose a fellow's going to sleep when-----"

Stacy struggled slowly to his feet when he saw the drawn faces of his companions.

"Was that another of them?" he asked hesitatingly.

"Yes," answered Tad, with a nod. "It is grand, but terrible."

"I don't see anything grand about it. I guess I won't lie down again.

I never can sleep any more after being awakened from my first nap,"

declared the fat boy.

No one slept for the rest of the night. The bombardment continued at intervals all through the black, terrifying night. The Colorado, into which billions of gallons of water had been dumped, was rising rapidly, an angry, threatening flood.

"Is there any danger of the river overflowing on us?" asked Professor Zepplin.

"No. No single night's rain would do it. The rain is pretty nearly ended now, as you can see for yourself. But there's no telling how long those fellows will continue to roll down. I've seen the same thing before, but this is the worst," declared Dad.

"All on account of the Pony Rider Boys," piped Stacy. "Miss Nature is determined to give us our money's worth in experience. I've had mine already. She can't quit any too soon to suit me."

After a time the guide crept out, his ears keyed sharply to catch warning sounds from above. Nance had been out but a moment when he darted back under the protecting ledge. He was just in time. A giant boulder struck the earth right in front of their place of refuge. From that moment on no one ventured out. About an hour before daylight, the storm having lulled, the failing boulders coming down with less frequency, all hands sank down on their wet blankets one by one, and dropped off to sleep.

When they awakened the day had dawned. The sun was glowing on the peaks of Pluto Pyramid and the Algonkin Terraces far above them on the opposite side of the gorge. Tad Butler was the first to open his eyes that morning. He sprang up with a shout.

"Sleepy heads! Turn out!"