Charles C. Gillispie is Dayton-Stockton Professor of History of Science, Emeritus at Princeton University. This article is adapted from a talk Dr. Gillispie recently gave before the American Philosophical Society. He is the author of The Montgolfier Brothers and the Invention of Aviation (Princeton University Press, 1983). For this article he has drawn also on the account of Blanchard’s exploit in Tom D. Crouch’s The Eagle Aloft: Two Centuries of the Balloon in America (Smithsonian Institution Press, 1983).