Perpetual Motion as used in this book means what it is usually understood to mean--Self-Motive Power--a machine that furnishes the power to keep its parts going as a machine. In this sense Perpetual Motion has always engaged the minds of many, many people--and what is more natural? As soon as a boy begins to take an interest in moving parts of machinery, vehicles, locomotives, and what not, he perceives that the application of power results in the motion of bodies, and again that bodies in motion are productive of power. A wheel moved by muscular, or other mechanical power, is made by machinery to elevate water, and elevated water can be made in descending to run machinery. The windlass, or other wheel, turned by applied force, lifts buckets from wells--raises stone, and elevates heavy bodies, if desired. Heavy bodies descending can be, and are used through means of machinery to make machinery run. A great many similar illustrations could be given. What, then, is more natural than that a boy with an active mind who is at all mechanically turned, as most boys are, begins to wonder why, if wheels lift stones, and if stones descending make wheels run, cannot a machine be made that will lift stones, or other weights, and in turn be run by the descent of the lifted stones, or other weights? Why, if the turning of wheels lift water, and if descending water makes wheels go, should not an adaptation be made by which the same machine will elevate water, and be run by the descent of the elevated water? That it cannot be done is now the consensus of opinion of all technically trained mechanics, but, that it can not be done, and why it can not be done, is sure not to occur to the boy, nor to the man who has only a strong natural mechanical sense to guide him, and has not the advantage of technical training. Again, it is well known that many, many men have spent considerable sums of money and given hours and hours, and days, and months, and years of close and careful thought, and experiment to the production of a machine that will accomplish Perpetual Motion, and that many have announced to the world that they had succeeded in its accomplishment, but that all their devices so far have turned out failures.