the direction and the pace of human life are set by the big cities, and these constitute now a single network of interdependent thought and activity, linked together by innumerable commercial, political and cultural relationships, so that a movement in any part immediately affects every other. Even in the most primitive areas the bus, the radio and the bulldozer move inexorably in, and when the necessities of world war or world commerce dictate it, anything from the jungles of Papua to the ice fields