It was a bright, clear morning. A large crowd had gathered at Niagara Falls to see the famous Charles Blondin walk over it on a tightrope. The sun glistened on the cascading torrent as it rushed over the precipice. From below came the ceaseless thunder of the plunging cataract.

The world’s greatest tightrope walker briefly tested the taut strand that reached across to the opposite bank. Then he took his long pole and, balancing himself expertly, started across. The crowd followed every movement tensely. Step by step he moved forward. The people on the shore reacted nervously to every sharp motion of the balancin…