river. Tad and Chunky followed him.

"We are going to have a storm," said Dad.

"A heavy one?" asked Tad.

"A regular hummer!"

"Rain?"

"Everything. The whole thing. I'm sorry now that we didn't go back up
the trail, but maybe we'd never got up before we were caught. However,
we're pretty safe down here, unless-----"

"Unless what?" piped Chunky.

"Unless we get wet," answered Nance, though Tad knew that was not what
was in the guide's mind.

Just as they were turning back to the camp there came an explosion that
seemed as if the walls of the Canyon had been rent in twain. Chunky
uttered a yell and leaped straight up into the air. Tad took firm hold
of the fat boy's arm.

"Don't be a fool. That was thunder and lightning. The lightning struck
somewhere in the Canyon. Isn't that it, Dad?"

Nance nodded.

"It's always doing that. It's been plugging away at Dad's Canyon for