The day on which I first conceived the idea of a boat trip down the Columbia hangs in a frame all its own in the corridors of my memory. It was a number of years ago-more than a dozen, I should say. Just previously I had contrived somehow to induce the Superintendent of the Yellowstone National Park to grant me permission to attempt a winter journey on ski around this most beautiful of America's great playgrounds. He had even sent a Government scout...