Cabinet: To begin with, would you paint a picture of the scene in the room at Weissenstein castle in the summer of 1721, when Leiden physics professor Willem ’s Gravesande and Viennese courtier Joseph Emanuel Fischer von Erlach came to view the mysterious machine whirring within it?

Simon Schaffer: We know surprisingly much about this setting. We know that, for example, it was a place that received a rather large number of visitors because of the spectacle of this extraordinary wheel, which had been installed in the fall of 1717, and was, let’s not forget, twelve feet in diameter, and very thick: eighteen inches. It was a very bulky wheel on a very long axle—not a slender and elegant piece of engineering. Though very large, the wheel went around extremely quickly, about once every two seconds. So it was not the London Eye. There was a cord wound around the axle that could be attached to other machines. In the room were a group of elegant gentlemen dressed in early eighteenth-century court dress, including our two visitors and, of course, the man who designed the wheel, whose real name was Johann Bessler but who went by the name of Orffyreus. He was a clockmaker in his early forties from Saxony in central Germany; he was a very well-known man, he had not come from nowhere.

Through the 1710s, Bessler had been engaged in a whole series of wheel shows in central Germany, around Leipzig and elsewhere, and had gotten into lots of pamphlet wars with critics who thought he was a conman. A few people, including Jakob Mahn, the clockmaker to whom he had apprenticed, claimed that they had thought of the idea first; others said that it was a trick; and some people said both! There was even one model maker, Andreas Gärtner, who said it was a trick, and then made a really good living showing the trick.

But the scene in the room at Weissenstein must have been extraordinary for a culture that—and this is something that we don’t always remember—was so familiar with wheelwork. After humans and animals, wheels driven by wind and water were by far the main source of motive power. So although the visitors had seen a lot of large wheels rotating, this one didn’t seem to have any visible source of motion. The visitors even manipulated the wheel, which I find very interesting. For example, they tried to stop it turning just by putting their hands on it, and were almost lifted off the ground. They eventually brought it to a halt, but when they restarted it, it went right back to its original speed incredibly quickly. And it worked equally well when it ran backwards. They couldn’t see what was inside the wheel, it wasn’t a wheel with spokes—it had a wooden frame covering the whole of its center. And they could hear things, weights falling, and were a bit puzzled by that. And then lastly, they examined the axle very closely. There were iron rods and brass cords on which the wheel rested. They couldn’t see any connection between the wheel and the outside room, and immediately wrote a number of people—notably Isaac Newton, president of the Royal Society, and John Desaguliers, the society’s curator—to say, “We’ve seen this wheel; it’s completely amazing and we’re not sure how it works.”

How do you think it worked? Obviously there was the rumor of concealment that you discuss, the idea that a servant hiding in an adjoining room was causing the wheel to move.

I’m pretty open-minded about that. The standard story is that there was someone next door—perhaps an old lady, though that seems a little implausible. But one can well imagine a connection to an adjacent space through the supports. The weights inside, according to Orffyreus’s own diagrams, don’t make sense. And the friction would have been huge given the dimensions of the wheel. I think the reasonable guess is that there was a connection to an externally driven pump of some sort, which would not be untypical.

So why, fifty years later, are studies of all these perpetual motion machines banned? You write that by 1775, on the suggestion of the mathematician Jean d’Alembert, the Paris Academy of Sciences had prohibited any consideration of such schemes. They were seen as a popular delusion, a baroque fantasy. Why do you think perpetual motion played such a central role in eighteenth-century philosophical culture?

I think it was fundamental because it sat at the juncture of three very important aspects of eighteenth-century scientific, technical, and commercial life. This may seem like a story of ancient superstition, but after the economic crash of 2008, maybe not so much. First of all, how do you measure the effect of a machine? In order to show that perpetual motion is technically impossible, you have to develop a very complex science of rational mechanics, more than was ever managed in the eighteenth century. One of the striking things about the debates on perpetual motion in the 1700s is that the Paris Academy’s ban on any discussion of them happens before the physicists in Paris can prove they’re impossible. To prove that perpetual motion of any kind is impossible, you need a theory of thermodynamics, which is not developed until the 1830s and 1840s at the earliest. So there’s a problem of what we might want to call audit: How can you measure the worth of something? How can you show the impossibility of this kind of production and consumption of energy?

Then there’s a problem of status. Who do you trust? Who are the people who are authorities when it comes to what machines can and cannot do? That’s not obvious at all. The people in the room include a physics professor and a courtier who made his living by designing and commissioning engines, and who was trained as an architect. It’s not at all obvious who to trust, right? The problem of credit and credibility is absolutely central to this.

And then finally there’s money. This is exactly the period of maximum credit crunch and financial and stock market bubbles. There were schemes launched to invest in such machines. The secret of Bessler’s machine was on sale, so it was said, for twenty thousand pounds. There were rumors on the London Stock Exchange of joint stock companies that were prepared to invest hundreds of thousands of pounds in perpetually moving wheels. And just as it was very hard to work out the effect of the machine, and very hard to work out who you should trust to judge it, it was extremely hard to work out what a viable investment looked like in the wake of the collapse of the South Sea Bubble the previous year, which had adversely affected a lot of people, including Newton, who seems to have had around twenty thousand pounds (two million pounds in modern money) invested in the South Sea Company. It’s also worth noting that wheels—for pumps, for transport—were often at the center of the catchpenny schemes that flourished in the late 1710s and early 1720s.

So perpetual motion machines were situated at the intersection of the market, science, and technology, which was then the most dynamic area of the European economy, as it is now.

You closely connect Bessler’s machine with water wheels and steam engines. Thomas Newcomen’s engines had recently been set up in British mines, and in 1721 Fischer von Erlach was in Kassel helping install these steam engines in Germany. Were steam engines considered almost as magical at that time as perpetual motion machines?

They were not seen as magical in that way, but in two respects they were absolutely comparable. One was that they seemed to offer the possibility of almost endless mechanical effect. We sometimes miss this point about Newcomen engines—it wasn’t just that they were unusually powerful, which they were, but that they promised the possibility of regular work, in principle forever. And why does that matter? It matters for a particular economic reason, which is that they were going to be used to drive pumps, particularly in deep mines, where you have to keep pumps running forever in order to maintain the water level. So the sense of very permanent machinery was there in the first stationary steam engines.

The other aspect in which they resembled the wheels was that their mode of working was certainly not understood by very many people. If you look at the stationary steam engines that the British had designed and then their agents would install in central and western Europe, especially in the Low Countries, from the 1720s onwards, they are the coming together of three different but related technologies. You needed technology that was capable of building very long, very robust metal cylinders. And that technology comes from gunnery. So exactly the same technology that you would use to make gun barrels was used to make the big cylinders for the steam engines. Secondly, you needed technology that could produce a regular and controllable source of heat in a large container. And that’s a distillery, right? And thirdly, you needed wheelwork. You needed a system of wheel-driven, geared balances that could turn circular motion into vertical motion, and vice versa. And that comes from the clock trade. So like a lot of perpetual motion machines, steam engines were absolutely dependent on clockmakers.

And putting together distillation, clock making, and gunnery limits, to put it mildly, the number of places where these stationary steam engines are likely to be designed. You need to be a warlike, whiskey-drinking (or at least alcohol-drinking), clock-making, time-sensitive, ingenious bunch of blokes. And that kind of means England in this period, because it’s hardly anywhere else that you get all those things in the same place at the same time. And for that reason, foreign observers found them puzzling; not magical, but certainly mysterious.

And there was obviously a lot of industrial espionage. Leibniz warned a colleague that there would be resistance by mine administrators to the new steam techniques. And he also argued that manpower should only be used for skilled tasks in the future and machines would free us. Was there anxiety, corresponding with the idea there was a servant in the machine, that we would all become servants to these machines?

I don’t think that anxiety is very marked yet, for two reasons. One is that they’re not yet delivering that kind of output. Even the machines that don’t rely on trickery break down regularly, as is usual with machinery, especially cutting-edge machinery. The trick is not invention but maintenance; so the aftersale is crucial to distribution here, at least as crucial as the espionage is in the first place. You needed engineers who were more or less on call to fix, repair, re-erect, and maintain the device once it was installed. They break down, fall to bits, blow up, stop working at regular intervals, and that’s true right through the 1700s, even, and especially, in the case of James Watt’s engines in the 1770s and 1780s. So I don’t see in early or mid-eighteenth century journalism or publicity a very strong sense that we are all going to be servants of these in fact rather unreliable bits of machinery.