On 19 September 1783 a large linen and paper balloon, painted blue and decorated with gold fleurs de lis, was inflated in the forecourt of the palace of Versailles over a fire of straw and wool. Louis XVI and Marie Antoinette were watching, along with a crowd estimated at over a hundred thousand.
Slung underneath it in a wicker cage were a sheep called Montauciel, which translates as climb to the sky, a duck and a rooster. The balloon rose, drifted for about eight minutes over roughly three kilometres, and came down in a wood at Vaucresson. When it was reached, the sheep was standing calmly and, by several accounts, eating the straw.
It is the most charming experiment of the eighteenth century, and it was a controlled test of a serious question.
The Question Was Whether Altitude Kills
Nobody knew what happened to a living body a few hundred metres up. There was genuine concern in the medical opinion of the day that the air at height might be unbreathable, or that the absence of the usual pressure might cause harm.
The choice of animals is the part that shows this was designed rather than staged for the court.
- The sheep was the subject. Its physiology was held to be reasonably similar to a human’s, so what happened to it was taken to indicate what would happen to a person
- The duck was the control. It flies at altitude routinely, so if the duck came down harmed, the harm would have to be attributed to the flight itself rather than to height
- The rooster was a second control: a bird that does not fly high, so any difference between the two birds would be informative
All three survived. The rooster had a damaged wing, and a witness stated that it had been kicked by the sheep before takeoff, which is the sort of detail nobody invents.
The king had originally proposed sending up two condemned criminals. Jean François Pilâtre de Rozier, who wanted the honour himself, argued against it, and the animal flight was the compromise.
The Brothers Were Wrong About Why It Worked
Joseph Michel and Jacques Étienne Montgolfier ran a successful paper manufacturing business at Annonay. Their first public demonstration on 4 June 1783 raised an unmanned balloon of sackcloth and paper about two kilometres.
Their explanation of the lift was incorrect in an interesting way. They believed they had discovered a new gas, produced by combustion, which they called Montgolfier gas and which was supposed to be intrinsically buoyant. Since smoke seemed to be the visible sign of it, they burned damp straw, wool and, according to several accounts, old shoes, to make the fire as smoky as possible.
The actual mechanism is that heating air makes it expand, so a given volume of hot air weighs less than the same volume of cold air, and the balloon floats for the same reason a cork does. The smoke contributes nothing but soot, and the wool and shoes were making the fire dirtier rather than hotter.
The correct account had been available in principle since Torricelli established that air has weight and exerts pressure in the 1640s. What the Montgolfiers had was not the physics but the practical realisation that a large enough envelope of light material could hold enough hot air to lift a load, which nobody had bothered to try.
The Rival With the Right Gas
Ten days after the Annonay demonstration, the Academy of Sciences funded a competing approach by the physicist Jacques Charles, who understood that hydrogen, then called inflammable air, is far lighter than air and does not need a fire.
The difficulty was making enough of it and holding it in. Charles worked with the Robert brothers, who developed a silk fabric sealed with a rubber solution, and produced the gas by pouring sulphuric acid onto iron filings, a process that took several days and generated so much heat that the apparatus had to be cooled.
His unmanned balloon launched from the Champ de Mars on 27 August 1783 and came down in the village of Gonesse, where the inhabitants attacked it with pitchforks and flails and tore it apart, having no framework at all for what had just fallen out of the sky. The government subsequently issued a public notice explaining that balloons were harmless.
The chemistry involved was being clarified at exactly that moment. Lavoisier was in the middle of dismantling phlogiston theory, had established that year that water is a compound of hydrogen and oxygen, and sat on the Academy commission that reported on the Montgolfier experiments.
Two Months to the First Human Flight
The animals having survived, the way was clear. On 21 November 1783, Pilâtre de Rozier and the Marquis d’Arlandes lifted off from the Château de la Muette in a Montgolfier balloon and flew for about twenty five minutes across Paris, some nine kilometres, tending the fire and putting out sparks in the fabric with wet sponges as they went.
Ten days later Charles and Nicolas Louis Robert flew a hydrogen balloon from the Tuileries, reached about five hundred metres, and travelled thirty six kilometres. After landing, Charles went up alone, rose to around three thousand metres, experienced pain in his ears, and became the first person to watch the sun set twice in one day. He never flew again.
Charles’s design was essentially the modern gas balloon: a valve at the top to release gas, ballast to control descent, a net distributing the load, and a barometer to measure altitude.
Benjamin Franklin, then American minister in Paris and by that point the most famous experimenter alive, watched the December flight from his carriage. Asked by a sceptical spectator what possible use the thing could be, he is reported to have replied with a question: what use is a newborn baby?
What It Cost and What It Started
Pilâtre de Rozier died in June 1785 attempting to cross the Channel in a hybrid craft that combined a hydrogen envelope with a hot air burner underneath it, an arrangement whose flaw is easy to see now. He and his companion Pierre Romain were the first fatalities of powered flight.
Within eleven years the technology was military. The French Aerostatic Corps used a tethered hydrogen balloon for observation at the Battle of Fleurus in 1794, and reconnaissance from the air changed what a commander could know about a battlefield.
Ballooning also became the first way to take instruments where no instruments had been. In the following decades scientists carried barometers, thermometers and hygrometers upwards to measure how the atmosphere changes with altitude, and in 1862 James Glaisher and Henry Coxwell went so high over England that Glaisher lost consciousness and Coxwell, whose hands had frozen, pulled the release valve with his teeth.
The Sheep
Montauciel was granted a place in the royal menagerie at Versailles for the rest of its life, which is a reasonable pension for eight minutes of work.
The experiment is remembered as a curiosity, and it was better designed than most of what preceded it. Somebody asked a question that could be answered by observation, chose a subject and two controls, ran it in public in front of witnesses who could not be accused of collusion, and got a clear result. Two months later a man went up on the strength of it.
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