Guillaume Amontons: The Deaf Man Who Measured Resistance
In 1699 a man who had never attended a university and could barely hear stood before the Académie Royale des Sciences and told its members that they had been ignoring something. Machines mattered enormously, he argued, and nobody was paying proper attention to friction. The paper was called *De la Résistance Causée dans les Machines*. It was controversial, it was checked, and within five years its conclusions had passed into engineering practice, where — three centuries and an entire discipline of surface physics later — they remain.
The Boy Who Skipped the University
Guillaume Amontons was born in Paris on 31 August 1663, the son of a lawyer from Normandy who had moved to the capital. While he was still young he lost most of his hearing, and for the rest of his life he was substantially deaf.
He never enrolled at a university. What he did instead was teach himself: mathematics, the physical sciences, celestial mechanics, and alongside them the practical trades of drawing, surveying and architecture. His deafness has often been treated as a romantic detail, but it is more usefully read as a constraint that shaped his method. A man who cannot easily follow lectures and disputation is thrown back on things he can look at and handle. Amontons became a builder of instruments, and thought through his hands.
Characteristically, his route into mechanics ran through perpetual motion machines — an obsession that led him, as it led few of its other victims, into a serious mathematical treatment of how mechanical systems actually behave.
Instruments
His first period of work was that of an improver of devices. He produced a hygrometer in 1687 and, in 1695, both a barometer and an air thermometer. He demonstrated an optical telegraph, and he designed a clepsydra — a water clock — intended to keep time at sea, which he described in his 1695 book *Remarques et expériences physiques sur la construction d'une nouvelle clepsydre*. He was admitted to the Académie des Sciences in 1690.
Instrument-making was not a sideline to his physics; it was his physics. Every result he is remembered for came out of apparatus he had built to make a quantity visible.
Springs and Grease
The friction work rests on a rig of elegant simplicity. Amontons used leaf springs to press a load onto the substrate and coiled springs to measure the tangential resistance to sliding — load in, resistance out, both read off a spring. He tested iron, copper, lead and wood, and he spread the surfaces with old fat.
That detail matters more than it looks. Because his specimens were greased, what Amontons was actually measuring was boundary lubrication rather than clean dry sliding — a fact modern tribologists note when explaining both the accuracy and the limits of what he found. What he found was this: the resistance is proportional to the load, and it is independent of the apparent area of contact. He also reported that for his greased materials the ratio of friction to load came out at about one-third — the quantity now called the coefficient of friction.
He did not stop at measurement. Amontons offered a physical explanation, arguing that friction arises from the geometry of surface irregularities — asperities, in the modern word — and, remarkably, noting that rigid and elastic asperities would produce equivalent resistance by different mechanisms. Then he did the thing that separates a scientist from a natural philosopher: he supplied rules of calculation and lookup tables so that working engineers could apply the results without doing the arithmetic themselves.
Cold at the End of the Scale
His thermometry produced the other result that carries his name. Working with air, Amontons established that the pressure of a gas rises by roughly a third between the temperature of cold and the boiling point of water — the pressure-temperature relation now known as Amontons' law, and one of the foundations on which the gas laws were later assembled.
Its most striking consequence he drew himself. If pressure falls in step with temperature, then there is a temperature at which it would fall to nothing — a floor to cold. Amontons put that floor at about −240 degrees Celsius. He was reasoning his way to absolute zero from a column of air in a glass tube, roughly a century before anyone could verify it.
The Fire Mill
Also in 1699 he built the *moulin à feu*, a fire mill: a wheel driven by the expansion of heated air. It is a hot air engine, arrived at more than a hundred years before Stirling, with a calculated capacity of thirty-nine horsepower — a match for nineteenth-century hot air engines other than Ericsson's caloric machine.
Why Guillaume Is Called a Genius
The friction results were not, strictly, new. Leonardo da Vinci had observed two centuries earlier that resistance is proportional to load and independent of contact area, putting the coefficient at about a quarter; the standard account calls Amontons' 1699 paper a rediscovery. Any honest case starts there.
What is defensible is what Amontons added. Leonardo preferred imaginative ideas and elegant theories to practical verification and, with no scientific society, journal or peers to answer to, left his insight where working engineers could never find it. Amontons belonged to a culture that valued experiment over elegance and exploited it fully: apparatus, repeatable measurement, publication through the Académie, verification by the Académie's president, and tables designed for people who would never read the paper. Within five years his laws had been confirmed twice and were in the hands of machine-builders. That is why the Materials Research Society's historical note calls him the father of modern studies of friction.
The counter-case is real. He was not first; his absolute zero was off by more than thirty degrees; his specimens were greased, so the laws of dry friction were established on lubricated surfaces. Coulomb had to verify them in 1781 and add the third law, which is why they are properly the Amontons-Coulomb laws, and they remain approximations that fail at the scales surface physics now probes. The genius here is not originality of conception but an undervalued kind of intelligence: knowing which quantity to measure, building the thing that measures it, and putting the answer where it can be used.
What the Engineers Kept
Amontons died in Paris on 11 October 1705, aged forty-two. A crater on the Moon carries his name, and Duncan Dowson placed him among the twenty-three "Men of Tribology" — the founding figures of the science of rubbing surfaces.
His practical legacy is unusually durable. The gas relation he found fed into thermodynamics; the floor of cold he calculated became a real constant of physics; and the two rules he pulled out of a spring rig and a lump of old fat are still, three hundred years on, the first thing an engineer applies when something has to slide against something else.
Achievements
- Worked as physicist, inventor and mechanic
