In 1861, Henry Dircks, a civil engineer, of London, published a work entitled "Perpetuum Mobile; or, Search for Self-Motive Power, During the Seventeenth, Eighteenth and Nineteenth Centuries." The book contains 599 pages, and was followed in 1870, by a second series by the same author entitled "Perpetuum Mobile, or a History of the Search for Self-Motive Power from the Thirteenth, to the Nineteenth Century." In these two books there is amassed a wonderful amount of material showing on the part of the author diligence, great patience and wide and thorough search. The author of these works was not enamoured of his subject, and his books clearly show that he was not writing them because of any interest he had in the subject of Perpetual Motion. On the contrary, they appear to have been written because of a deep detestation entertained by the author for the subject of Perpetual Motion, and a contemptuous pity for any one seriously interested in the subject. Mr. Dircks's works may be said to be the works of a scold. His sentiments were deep, and his impulses strong, which accounts for the vast amount of labor he did in the preparation of his books. Those books are now out of print, and it is believed by the author of this book that they may well remain so. They contain much material that no one would be justified in wading through. The most complicated mechanisms devised by enthusiastic dreamers are shown in the same detail with which the inventors described them in presenting them to the public, or to the patent offices. Little is to be gained by this. So complicated are many of the devices that only technically trained engineers could read them understandingly, and few technically trained engineers are now greatly interested in self-motive power devices. We believe that every useful or interesting purpose is served if enough devices are collected, classified and presented to show the various principles relied upon by the inventors; with an explanation of why they failed-i. e., wherein the principles relied upon are wrong, and while possibly not out of harmony with any mechanical principles then known, are entirely out of harmony with principles since discovered and now well known. In the preparation of this volume a vast amount of the information furnished by the two works of Mr. Dircks has been rearranged, reclassified, and used. Everyone who has to any extent, by environment, associated with the mass of people who are not technically educated, knows that the persons who are still interested in the subject of Perpetual Motion, and who still seek its attainment, are not technically trained engineers or mathematicians, but for the greater part untrained people of naturally strong mechanical sense, and of natural mechanical and mathematical adaptation. This book is written for the perusal of that large class of people. It is not designed as an argument either for or against the possibility of the attainment of Perpetual Motion. The author is content to classify and present-clearly, it is hoped-the leading endeavors that have been known in that field of effort, and to explain their failure. It is believed by the author that the perusal of the present volume by anyone whose mind has been attracted by the subject of Perpetual Motion will result in an enlightenment, and, it is also believed, will have a tendency to direct his mind from a struggle with theories long ago exploded, and may result in directing his efforts to things practical, and not without hope of attainment. This work is offered only to minds mechanically or mathematically inclined. It is not even hoped that it will interest people who prefer fiction to fact, nor people who read simply for idle entertainment.