"IN THE preparation of this book the author has tried to give an interesting account of the invention and workings of a few of the machines and mechanical processes that are making the history of our time more wonderful and more dramatic than that of any other age since the world began. For heroic devotion to science in the face of danger and the scorn of their fellowmen, there is no class who have made a better record than inventors. Most inventions, too, are far more than scientific calculation, and it is the human story of the various factors in this great age of invention that is here set forth for boy readers." -Preface