"Churchill warned them now: "When you are drifting down the stream of Niagara, it may easily happen that from time to time you run into a reach of quite smooth water, or that a bend in the river or a change in the wind may make the roar of the falls seem far more distant. But"--his voice dropped a register, and only those who strained could hear--"your hazard and your preoccupation are in no way affected thereby."