THE War of the American Revolution had just come to a close when the French people, and Franklin with them, were offered a new interest and a fresh topic for speculation: human flight. After the Montgolfier brothers had several times sent aloft unmanned balloons inflated with hot air, two Frenchmen, Pilâtre de Rozier and the Marquis d'Arlandes, embarked in one of the Montgolfier craft, November 21, 1783, on what proved to be the first successful free-balloon flight of human beings in history, taking off from a spot near Franklin's house at Passy. Ten days later two other Frenchmen, Jacques Alexandre César Charles and one of the two Robert brothers, ascended from the Tuileries Gardens in Paris in a hydrogen-filled balloon. Franklin, a fascinated observer of both flights, reported these events to his scientific friends in other countries, especially to Sir Joseph Banks, the president of the Royal Society in London.
That the balloon was an astonishing toy many observers admitted, but of what possible good? What good, retorted Franklin in a reply that went the rounds of Paris, is a new-born baby? He was soon speculating on the effects of the new invention. In the second passage here, from a letter to Ingenhousz in Vienna a few weeks later, he proved, ironically, a better prophet of how air power might be used in war than of how it might contribute to universal peace.
Passy, December 1, 1783
In mine of yesterday, I promis'd to give you an Account of Messrs. Charles and Robert's Experiment, which was to have been made on this Day, and at which I intended to be present. Being a little indispos'd, and the Air cool, and the Ground damp, I declin'd going into the Garden of