Produced by Steven Gibbs, Greg Bergquist and the Online Distributed Proofreading Team at https://www.pgdp.net Transcriber's Note The punctuation and spelling from the original text have been faithfully preserved. Only obvious typographical errors have been corrected. Subscripts are represented as X_1. Superscripts are represented by X^1. HOW IT WORKS AUTHOR'S NOTE. I beg to thank the following gentlemen and firms for the help they have given me in connection with the letterpress and illustrations of "How It Works"-- Messrs. F.J.C. Pole and M.G. Tweedie (for revision of MS.); W. Lineham; J.F. Kendall; E. Edser; A.D. Helps; J. Limb; The Edison Bell Phonograph Co.; Messrs. Holmes and Co.; The Pelton Wheel Co.; Messrs. Babcock and Wilcox; Messrs. Siebe, Gorman, and Co.; Messrs. Negretti and Zambra; Messrs. Chubb; The Yale Lock Co.; The Micrometer Engineering Co.; Messrs. Marshall and Sons; The Maignen Filter Co.; Messrs. Broadwood and Co. [Illustration: ON THE FOOTPLATE OF A LOCOMOTIVE.] How It Works Dealing in Simple Language with Steam, Electricity, Light, Heat, Sound, Hydraulics, Optics, etc. and with their applications to Apparatus in Common Use By ARCHIBALD WILLIAMS Author of "The Romance of Modern Invention," "The Romance of Mining," etc., etc. THOMAS NELSON AND SONS London, Edinburgh, Dublin, and New York PREFACE. How does it work? This question has been put to me so often by persons young and old that I have at last decided to answer it in such a manner that a much larger public than that with which I have personal acquaintance may be able to satisfy themselves as to the principles underlying many of the mechanisms met with in everyday life. In order to include steam, electricity, optics, hydraulics, thermics, light, and a variety of detached mechanisms which cannot be classified under any one of these heads, within the compass of about 450 pages, I have to be content with a comparatively brief treatment of each subject. This brevity has in turn compelled me to deal with principles rather than with detailed descriptions of individual devices--though in several cases recognized types are examined. The reader will look in vain for accounts of the Yerkes telescope, of the latest thing in motor cars, and of the largest locomotive. But he will be put in the way of understanding the essential nature of _all_ telescopes, motors, and steam-engines so far as they are at present developed, which I think may be of greater ultimate profit to the uninitiated. While careful to avoid puzzling the reader by the use of mysterious phraseology I consider that the parts of a machine should be given their technical names wherever possible. To prevent misconception, many of the diagrams accompanying the letterpress have words as well as letters written on them. This course also obviates the wearisome reference from text to diagram necessitated by the use of solitary letters or figures.