Johann Bessler's Perpetual Motion Wheels Part III

Professor 'sGravesande's letter to Newton

Probably the most important written account that we have from a very well-qualified contemporary "hands-on" witness of one of Bessler's wheels (the Weissenstein wheel), is the letter written by Professor Willem Jacob van 'sGravesande of Leiden University to Sir Isaac Newton. This letter was published in 'sGravesande's Oeuvres philosophiques et mathématiques, which is now available on-line, e.g. at http://cerebro.xu.edu/math/Sources/sGravesande/gravesande.html. The letter is in Vol I, p303.

Up to now, English-language writers all seem to have relied on the translation of this letter that appeared in the Annual Register, for the year 1763, Vol 6, p126-128 (reprinted in Henry Dircks' Perpetuum Mobile..., 1861, p38.) This translation is generally accurate, but it does have one error and two omissions. Since I'm still reasonably fluent in reading French, I've made my own unabridged, more literal translation below (with the main corrections highlighted in bold type):—

Translation:—

Letter to Mr. Neuwton (sic) On a Machine invented by Orffyreus.

Doctor Desaguliers has doubtless shown you a letter, which Baron Fischer wrote to him a while ago, about the Wheel of Orffyreus, which the inventor claims to be a perpetual motion. The Landgrave wished that I also should examine the machine. This Prince who loves the Sciences and the Fine Arts, and who by the help that he gives to all those who follow them with some success, doesn't neglect any opportunity to render the inventions which are presented to him useful to the public, wished to see that machine made known everywhere, and put into the hands of people more skilful than the inventor, so as not to lose the benefits that would naturally attend such a singular invention.

I thought, Sir, that you would not be displeased to have a rather detailed account of what can be seen from an external examination of a machine concerning which sentiments are so divided, and which is opposed by almost all the accomplished mathematicians. A majority maintain the impossibility of perpetual motion, whence comes the scant attention that has been paid to the machine of Orffyreus. I know I am inferior to those who have given demonstrations of the impossibility of this motion, nevertheless to explain to you the sentiments with which I examined this machine, I have the honour to tell you that about seven years ago I believe I discovered the paralogism of these demonstrations, in that they could not be applicable to all possible machines; and since then I have always been convinced that one could demonstrate that perpetual motion was not contradictory; and it seemed to me that Mr. Leibnitz was wrong to regard as an axiom the impossibility of perpetual motion; which was nevertheless at the basis of part of his philosophy. Notwithstanding this conviction, I was very far from believing that Orffyreus was accomplished enough to discover perpetual motion. I considered that perpetual motion would not be discovered until after many other inventions, if ever. But since I have examined the machine, I don't know how to express my astonishment.

The inventor has a genius for mechanics, but is not in the least a profound mathematician, however that machine has something surprising about it, even if it be fraudulent. The following is about the machine itself, the interior of which the inventor will not permit to be seen, lest anyone should steal his secret from him. It is a drum about 14 inches thick by 12 feet diameter; it is very light, being made of several wooden boards assembled with other pieces of wood, in such a way that the interior could be seen from all sides if not for an oilcloth which covers all of the drum. This drum is traversed by an axle of about six inches diameter, terminated at its ends by three-quarter inch iron journals, on which the machine turns. I examined these journals, and I am convinced that nothing from outside contributes to the movement of the machine. I turned the drum very slowly, and it stood still as soon as I took my hand away; I made it make a turn or two in that way. Then I made it move slightly more quickly; again I made it make a turn or two; but then I was obliged to hold it back continually; for having let it go, it reached in less than two turns its maximum velocity, so that it made twenty-five or twenty-six turns per minute. It kept up this motion some time ago for two months in a sealed room, in which it was impossible that there could have been any fraud. His Serene Highness had the room opened and had the machine stopped after that time, because, as it was only a prototype, the materials might not be strong enough to stand a long period of running.

The Landgrave was present at the examination which I made of the machine. I took the liberty of asking His Serene Highness who has seen the interior of the drum, if something might change in its interior after a certain period of running; also if there might be some components in which fraud could be suspected; His Serene Highness assured me that this was not so, and that the machine was very simple.

You see Sir, that I have not seen enough of it to assure myself that the principle of motion which is certainly in the drum, has really been demonstrated to be a perpetual motion, but I still believe my strong presumption in favour of the inventor should not be denied.

The Landgrave in his generosity gave a worthy present to Orffyreus, to be let into the secret of the machine, with a promise never to part with it, or to reveal it until the inventor had derived other rewards for making his invention public. I know very well Sir, it is only in England that the sciences flourish sufficiently to find the inventor a worthy reward for his invention. It is simply a matter of assuring him of it if his machine proves to be a true perpetual motion. The inventor does not ask to touch the money until after the machine has been internally examined; such an examination could not reasonably be demanded before the reward had been assured. Since it is a matter of usefulness to the public, and of the advancement of science, to discover whether the invention is real or a fraud, I thought that you might like to have this account. I am, etc.

Comment:—

In the 1763 translation,  'sGravesande's remark "I made it make a turn or two" (which he says twice) has been omitted. The importance of this remark is that it removes any possible doubt that a slowly-turned wheel might still have been able to start running if turned through a sufficiently large angle. (I think that this was precisely what he was trying to find out).

The interesting and somewhat puzzling fact that  'sGravesande makes clear is that the wheel never, ever, tried to "run away" when turned slowly, and yet that large, high-inertia wheel accelerated to its maximum velocity in less than two revolutions when started off with only slightly more external energy. That implies the expenditure of quite a lot of internal energy. But then it would never go beyond its characteristic rotational speed of 26 rpm!