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.