The activities of George Westinghouse were many and varied, and many different activities went on simultaneously. He dealt in the same week, and often in the same day, with organization, financial and executive affairs, commercial affairs, and the engineering details of half a dozen companies in two hemispheres. It was decided to treat each topic by itself without regard to what might be going on at the time in other fields, with a short preliminary chapter to which the reader might return to orient himself should he care, for instance, to know what other serious things were in hand at a critical moment in the history of the air brake. It was hoped that by this treatment a certain continuity of impression might be kept in each story told by itself.