This is a biography of a major American inventor, who obtained more than 350 patents during his lifetime. Elmer Sperry contributed greatly to the technological changes occurring between 1880 and 1930. He was best known for the Sperry gyrocompass and automatic pilot, and his inventions included arc-light systems, mining machinery, electric automobiles and streetcars, and electrochemical processes. Characteristic of his various inventions were feedback controls which have made automation a fact of life. The book won the Dexter Prize of the Society for the History of Technology.