"Although interest in such a craft dates from the 13th cent., the balloon was not actually invented until the late 18th cent., when two French brothers, Joseph and Jacques Étienne Montgolfier, experimented with inverted paper and cloth bags filled with heated air and, in 1783, caused a linen bag about 100 ft (30 m) in diameter to rise in the air. In the same year the Frenchman Pilatre de Rozier made one of the first balloon ascents by man, rising in a hot-air-filled captive balloon (i.e., one made fast by a mooring cable to prevent free flight) to a height of 84 ft (26 m). In 1766 the English scientist Henry Cavendish had shown that hydrogen was seven times lighter than air, and the usefulness of this gas in balloon ascension was demonstrated in Dec., 1783, by J. A. C. Charles of France, who with his associates successfully ascended in a hydrogen-filled balloon and traveled 27 mi (43 km) from the starting point.
The first ascent in England was made by James Tytler, a Scottish writer, in 1784, and in 1793 the French balloonist J. P. Blanchard made an ascent at Philadelphia. Blanchard, with Dr. John Jeffries, an American physician, also made the first sea voyage by balloon, crossing the English Channel in 1784. Among the noted balloon voyages of the 19th cent. was that made by the Swedish engineer S. A. Andree, who, in 1897, attempted unsuccessfully to reach the North Pole by balloon. In the American Civil War and World War I, captive balloons were used to observe troop movements and to direct gunfire. Captive balloons, called barrage balloons, were used as obstacles against low-flying aircraft in World War II."
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