Sick Heart River by John Buchan — Read

All next morning they smelt their way through the box-canyons, sometimes with the engine shut off and the Hares poling madly. There were two dangerous rapids, but navigation was made simpler by the fact that there were no split channels and no shallows. They were going through the limestone foothills, and the cliffs on either side were at least seven hundred feet high, sheer as a wall where they did not overhang. Johnny had a tale about the place. Once the Hares had been hunted by the Crees -- he thought it was the Crees, his own people, but it might have been the Dogribs. At that time the Big Hare River had come out of the mountains underground. The Hare boats were no match for the fleet Cree canoes, and the wretched tribe, fleeing upstream, looked for annihilation when they reached the end of the waterway. But to their amazement they found the mountains open before them and a passage through the canyons to the upper valley where was now the Hares' hunting camp. When they looked back there were no pursuing Crees, for the mountain wall had closed behind them. But some days later, when the disappointed enemy had gone back to their Athabaska swamps, the passage opened again, and the Hares could return when they pleased to the Mackenzie.

"Big magic," said Johnny. "I reckon them Hares got the story out of the Bible, when the missionaries had worked a bit on them, for it's mighty like the children of Israel and old Pharaoh."