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!"

Dad was on his feet with a bound. Then came the Professor, Ned and
Walter in the order named, with Stacy Brown limping along painfully at
the rear.

"How do you feel this fine morning?" glowed Tad, nodding at Stacy.

"I? Oh, I'm all bunged up. How's the weather?"

"Nature is smiling," answered Tad.

"All right. As long as she doesn't grin, I won't kick. If she grins
I'm blest if I'll stand for it."

"Whose turn is it to get breakfast?" questioned Ned.

"What little there is to get I will attend to," said Tad. "We are long
on experience but short on food."

Still, breakfast was a cheerful meal, even though all were still wet,
their muscles stiffened from sleeping in puddles, from which they were
obliged to dip the water for their coffee. They enjoyed the meal just
as much as if it had been a banquet, however.

Dad's face did not reflect the general joy that was apparent on the
faces