It would serve no useful purpose here to give an exhaustive historical account[1] of the vagaries of mankind in pursuit of the “perpetuum mobile.” The reader may refer to Henry Dircks's Perpetuum Mobile (2 vols., 1861 and 1870), from which, for the most part, we select the following facts.
By far the most numerous class of perpetual motions is that which seeks to utilize the action of gravity upon rigid solids. We have not read of any actual proposal of the kind, but the most obvious thing to imagine in this way would be to procure some substance which intercepts gravitational attraction. If this could be had, then, by introducing a plate of it underneath a body while it was raised, we could elevate the body without doing work; then, removing the plate, we could allow the body to fall and do work; eccentrics or other imposing device being added to move the gravitation intercepter, behold a perpetual motion complete! The great difficulty is that no one has found the proper material for an intercepter.
Fig. 1 represents one of the most ancient and oftenest-repeated of gravitational perpetual motions The idea is that the balls rolling in the compartments between the felloe and the rim of the wheel will, on the whole, so comport themselves that the moment about the centre of those on the descending side exceeds the moment of those on the ascending side. Endless devices, such as curved spokes, levers with elbow-joints, eccentrics, &c, have been proposed, for effecting this impossibility. The student of dynamics at once convinces himself that no machinery can effect any such result; because if we give the wheel a complete turn, so that each ball returns to its original position, the whole work done by the ball will, at the most, equal that done on it. We know that if the laws of motion be true, in each step the kinetic energy given to the whole system of wheel and balls is equal to that taken from the potential energy of the balls less what is dissipated in the form of heat by frictional forces, or vice versa, if the wheel and balls be losing kinetic energy—save that the friction in both cases leads to dissipation. So that, whatever the system may lose, it can, after it is left to itself, never gain energy during its motion.
The two most famous perpetual motions of history, viz. the wheels of the marquis of Worcester (d. 1667) and of Councillor Orffyraeus, were probably of this type. The marquis of Worcester gives the following account of his machine in his Century of Inventions (art 56)—
“To provide and make that all the Weights of the descending side of a Wheel shall be perpetually further from the Centre than those of the mounting side, and yet equal in number and heft to one side as the other. A most incredible thing, if not seen but tried before the late king (of blessed memory) in the Tower, by my directions, two Extraordinary Embassadors accompanying His Majesty, and the Duke of Richmond, and Duke Hamilton, with most of the Court attending him. The Wheel was 14 Foot over, and 40 Weights of 50 pounds apiece. Sir William Balfore, then Lieutenant of the Tower, can justify it, with several others They all saw that no sooner these great Weights passed the Diameter-line of the lower side, but they hung a foot further from the Centre, nor no sooner passed the Diameter-line of the upper side but they hung a foot nearer. Be pleased to Judge the consequence."
Orffyraeus (whose real name was Johann Ernst Elias Bessler) (1680–1745) also obtained distinguished patronage for his invention. His last wheel, for he appears to have constructed more than one, was 12 ft. in diameter and 1 ft. 2 in. broad; it consisted of a light framework of wood, covered in with oilcloth so that the interior was concealed, and was mounted on an axle which had no visible connexion with any external mover. It was examined and approved of by the landgrave of Hesse-Cassel, in whose castle at Weissenstein it is said to have gone for eight weeks in a sealed room. The most remarkable thing about this machine is that it evidently imposed upon the mathematician W. J. 'sGravesande, who wrote a letter to Newton giving an account of his examination of Orffyraeus's wheel undertaken at the request of the landgrave, wherein he professes himself dissatisfied with the proofs theretofore given of the impossibility of perpetual motion, and indicates his opinion that the invention of Orffyraeus is worthy of investigation. He himself, however, was not allowed to examine the interior of the wheel. The inventor seems to have destroyed it himself. One story is that he did so on account of difficulties with the landgrave's government as to a licence for it; another that he was annoyed at the examination by 'sGravesande, and wrote on the wall of the room contain in the fragments of his model that he had destroyed it because of the impertinent curiosity of 'sGravesande.
The overbalancing wheel perpetual motion seems to be as old as the 13th century. Dircks quotes an account of an invention by Wilars de Honecort, an architect whose sketchbook is still preserved in the Écoles des Chartes at Paris. De Honecort says, “Many a time have skilful workmen tried to contrive a wheel that shall turn of itself; here is a way to do it by means of an uneven number of mallets, or by quicksilver.” He thereupon gives a rude sketch of a wheel with mallets jointed to its circumference. It would appear from some of the manuscripts of Leonardo da Vinci that he had worked with similar notions.
Another scheme of the perpetual motionist is a water-wheel which shall feed its own mill-stream. This notion is probably as old as the first miller who experienced the difficulty of a dry season. One form is figured in the Mathematical Magic (1648) of Bishop Wilkins (1614–1672); the essential part of it is the water screw of Archimedes, which appears in many of the earlier machines of this class. Some of the later ones dispense with even the subtlety of the Water-screw, and boldly represent a water-wheel pumping the water upon its own buckets.
Perpetual motions founded on the hydro statical paradox are not uncommon; Denis Papin exposes one of these in the Philosophical Transactions for 1685. The most naive of these devices is that illustrated in fig. 2, the idea of which is that the larger quantity of water in the wider part of the vessel weighing more will overbalance the smaller quantity in the narrower part, so that the water will run over at C, and so on continually.
Capillary attraction has also been a favourite field for the vain quest; for, if by capillary action fluids can be made to disobey the law of never rising above their own level, what so easy as thus to produce a continual ascent and overflow, and thus perpetual motion? Various schemes of this kind, involving an endless band which should raise more water by its capillary action on one side than on the other, have been proposed. The most celebrated is that of Sir William Congreve (1772–1828). EFG (fig. 3) is an inclined plane over pulleys; at the top and bottom travels an endless band of sponge, abcd, and over this again an endless band of heavy weights jointed together. The whole stands over the surface of still water. The capillary action raises the water in ab, whereas the same thing cannot happen in the part ad, since the weights squeeze the water out. Hence, inch for inch, ab is heavier than ad; but we know that if ab were only just as heavy inch for inch as ad there would be equilibrium, if the heavy chain be also uniform; therefore the extra weight of ab will cause the chain to move round in the direction of the arrow, and this will go on continually.
The more recondite vehicles of energy, such as electricity and magnetism, are more seldom drawn upon by perpetual-motion inventors than might perhaps be expected. William Gilbert, in his treatise De Magnete, alludes to some of them, and Bishop Wilkins mentions among others a machine “wherein a loadstone is so disposed
- ↑ We may here notice, so far as more recent times are concerned, the claim of an American enthusiast, who, having worked a Hampson plant for liquefying air, stated that 3 lb of liquid air sufficed to liquefy ten, and of these ten seven could be employed as a source of motive power, whilst the remaining three could be utilized in the production of another 10 lb of the liquid gas. There was thus available an inexhaustible supply of energy! The absurdity of the proposition is obvious to any one acquainted with the laws of thermodynamics. Of more interest is the radium clock devised by the Hon R J Strutt. This consists of a vacuum vessel from the top of which depends a short tube containing a fragment of a radioactive substance. At the lower end of this tube there are two gold leaves as in an electroscope. Fused into the sides of the vacuum vessel at points where the extended gold leaves touch the glass are two platinum wires, the outer ends of which are earthed. The “clock” acts as follows. The radio-active substance emits a preponderating number of positively electrified particles, so that the leaves become charged and hence extended. On contact with the wires fused into the vessel, this charge is conducted away and the leaves fall together. The process is then repeated, and will continue until all the energy of the radium has been dissipated. This period is extremely long, for 1000 years must elapse before even half the radium has disappeared—[Ed]
