At the mouth of the Chute there was a great, knife-like rock, like a dragon's tooth, that cut the Chute into two roaring channels.

If a scow kept to the left-hand channel it was safe.

There would be a mighty roaring and thundering as it swept on its passage, but that roaring of the Chute, he told her, was like the barking of a harmless dog.
Only when a scow became unmanageable, or hit the Dragon's Tooth, or made the right-hand channel instead of the left, was there tragedy.
There was that delightful little note of laughter in Marette's throat when Kent told her that.
"You mean, Jeems, that if one of three possible things doesn't happen, we'll get through safely ?" "None of them is possible--with us," he corrected himself quickly.
"We've a tight little scow, we're not going to hit the rock, and we'll make the left-hand channel so smoothly you won't know when it happens." He smiled at her with splendid confidence.

"I've been through it a hundred times," he said.
He listened.

Then, suddenly, he drew out his watch.