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. INTRODUCTORY ESSAY Perpetual Motion as used in this book is to be taken in its conventional, and not in its strict literal sense. The strict literal analysis of the two words implies unceasing motion. Of this we have many illustrations--the tides, the waves of the ocean, the course of the earth around the sun, and in the movements of all heavenly and astronomical bodies. In fact, it is difficult to conceive in a strictly scientific sense of any substance having an entire absence of motion.