Artificial Clouds and Inflammable Air: The Science and Spectacle of the First Balloon Flights, 1783

Jane E. Boyd

Charles thought at first that the Montgolfiers had used hydrogen gas to lift their balloon, as no other lighter-than-air gas was known at the time, and he did not yet know that ordinary atmospheric air could expand enough when heated to lift such a structure. So he recruited two instrument makers, brothers Anne-Jean and Marie-Noël Robert, to help him generate an immense, unprecedented volume of hydrogen gas. To help pay for this expensive undertaking, naturalist and geologist Barthélemy Faujas de Saint-Fond opened a public subscription, selling tickets for a demonstration with time and place to be announced. Despite such vagueness, the elite of Paris quickly signed up, eager to be among the first to see this daring experiment.

Making Gases Fly

For balloons to truly take off, scientists needed to understand how gases worked. Though still in its infancy, the science of gases was advancing quickly. Inspired by Enlightenment beliefs in reason and progress, 18th-century natural philosophers were seeking to unlock nature’s mysteries, including the properties of air—invisible and untouchable, yet ubiquitous and necessary for life. Realizing that atmospheric air was not a single substance, scientists worked to separate air into its component gases, analyzing and observing the properties of each. Englishman Henry Cavendish had isolated hydrogen in 1766, naming it “inflammable air” for its readiness to burn. In the 1770s Joseph Priestley in England, Carl Wilhelm Scheele in Germany, and Antoine-Laurent Lavoisier in France all contributed to the discovery of oxygen. Priestley called his gas “dephlogisticated air” because it apparently lacked “phlogiston,” the universal component of fire then thought to reside in all combustible substances. In June 1783 Lavoisier proved that water was not an element but rather a combination of hydrogen and oxygen. He was soon able to overturn the dominant phlogiston theory, laying the groundwork for modern chemical terminology and methods. Charles would later make an important contribution to this effort in 1787, when he formulated the law of gases that now bears his name. Eventually elaborated by Joseph-Louis Gay-Lussac, Charles’s law states that under constant pressure the volume of a fixed weight of gas is directly proportional to its absolute temperature—a principle that would prove essential to ballooning.

To make his flying vessel a reality, Charles focused on producing enough “inflammable air” to fill a medium-sized cloth balloon, which was coated with gum in an effort to make it airtight and waterproof. Large quantities of hydrochloric acid were poured into a barrel of iron filings, with tubes and valves to control the resulting outflow of gas. The Robert brothers had invented an ingenious device to speed up the production of hydrogen: a sort of bureau with iron-lined drawers intended to give the acid more surface area of metal to work on. The apparatus did not function properly, however, so the team reverted to using the barrel. Finally, after innumerable technical difficulties and delays, they were ready. On 27 August 1783, just three months after the Montgolfiers’ hot-air demonstration in southern France, the world’s first unmanned hydrogen balloon took off from the Champ de Mars, the capital’s large military parade ground. As a violent storm began, the balloon shot straight up into the sky and was lost from view in the clouds within minutes.