urst through the chains of water,
stronger than iron and forged out upon the united waters.

At last we were upon the back of the Colorado, its powerful current
carrying us swiftly along.

"Hurrah!" yelled Jim, "we're off."

Tom and I were too breathless from the past struggle to yell, but we
threw up a triumphant hand. We did not look back to see what we had come
through. That we could never do on the Colorado, for there was always
something to look forward to that required immediate attention.

"There's a big canyon ahead," I yelled to Jim. "It's got the biggest
roar of any we have met yet."

"All right, Jo," answered Jim, "we will swing off to the first good
landing."

This we found without much difficulty and we got a good night's rest to
prepare us for the struggle that lay before us.

For the next two days we had a terrific struggle with this canyon, the
most dangerous that we had so far encountered. In fact it was in many
ways the worst we were to go through on the whole trip.

There was one place we ran through that struck me with terror. We came
upon it early one afternoon. There was a sharp plunge downward of the
river and on all sides it was beaten into foam among the rocks. In the
center there was a swift, clear run, that ended in big successive waves.

We took it fairly in the middle. Jim had become too good a steerer to be
beaten now. But when we struck the waves our boat plunged as in a heavy
sea. Much of it would have made one seasick.

One big red fellow curved over the bow, knocking me forward and I was
only saved from going overboard by grasping the side and holding on for
dear life. It seemed as if the deluge held me under for a full minute,
but it was only a few seconds.

My oar was shattered and I hastened to replace it with an extra one. We
carried several for just such emergencies.

"Hello!" exclaimed Tom, after this exciting episode, "just listen to
that thunder."

"Thunder!" cried Jim, "that isn't thunder. It's perfectly clear
overhead. There is not a storm within a hundred miles."

"What is it then?" demanded Tom.

Jim listened for a moment. There was no denying the sound. It was
different from the roar of the river. A deep rumbling bass with a
grinding sound to it.

"I know what it is!" he cried. "It is the big boulders at the bottom of
the river being rolled along by the current."

"Think of the force of it," I exclaimed. "I bet they are as big as a
horse."

"Nearer a