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.

New discoveries, or new applications of forces known to exist, illustrating some broad principle of science, have been the chief concern of the author in choosing the subjects to be taken up in the various chapters, so that it has been necessary to limit the scope of the book, except in one or two instances, to inventions that have come into general use within the last ten years. In "The Boy's Book of Inventions," "The Second Boy's Book of Inventions," and "Stories of Invention," Mr. Baker and Mr. Doubleday have told the stories of many of the greatest inventions up to 1904, including those of the gasoline motor, the wireless telegraph, the dirigible balloon, photography, the phonograph, submarine boats, etc. Consequently for the most part the important developments in some of these machines are treated briefly in the final chapters, while the earlier chapters are devoted to new inventions, which, if made before 1904, did not receive general notice until after that time.

Although the subjects treated in the earlier chapters are here spoken of as new inventions, all of them are not recent in the strictest sense of the word, for men had been working on the central idea of some of them for many years before they actually were developed to a stage where they could be patented and sent out into the world.

H. E. M.