The American scientist Samuel Pierpont Langley (1834-1906) was a pioneer experimenter with airplanes and in the science of aeronautics.

Samuel Langley was born in Roxbury, Mass., on Aug. 22, 1834. As a boy, he studied diligently and read widely in history, the classics, and various branches of science, but his formal education ended with graduation from high school in 1851.

For the next several years Langley worked as an engineer and architect. After a trip abroad in 1864-1865 to visit observatories and research centers, he received an assistantship in the Harvard Observatory, Cambridge, Mass. Later he was put in charge of the small observatory at the Naval Academy in Annapolis, Md. In 1867 he became director of the Allegheny Observatory and professor of physics and astronomy at the Western University of Pennsylvania (now the University of Pittsburgh).

During the next few years Langley devised and sold to the Pennsylvania Railroad a method of regulating railroad time from the observatory clock, and he made a number of visual observations of the solar spectrum, studying particularly the nature of sunspots. In 1878 he invented the bolometer, an instrument for measuring tiny quantities of heat. Through its use Langley was able to measure lunar and solar radiation, study the transparency of the atmosphere to different solar rays, and determine their greater intensity at high altitudes, even beyond the atmosphere altogether. He organized a famous expedition to Mt. Whitney, Calif., in 1881 to carry out this work. Afterward Langley was much in demand as a popular lecturer and author. A collection of his writings, The New Astronomy (1888), has become a classic in astronomical literature. Langley's concern was not with the traditional astronomy of position but with the newer physics of structure.

Langley was appointed secretary of the Smithsonian Institution in Washington, D. C., in 1887 and served in that post until his death. During this time he investigated the possibilities of manned flight, studying the lift and drift of moving plane surfaces on a sophisticated scientific basis. Experimenting with small models propelled by elastic strips, he worked out the mathematics of the problem. His contributions to aviation rest not only on the knowledge he acquired and shared with others or upon his successful long-distance flights of power-driven models, but also upon the dignity he brought, as a man of sound scientific reputation, to the new and often-ridiculed field of aeronautics.

In 1896 Langley flew a 14-foot steam-powered model for 3,000 feet with excellent stability, the craft touching down lightly after the fuel was exhausted. A second model flew 4,200 feet, or over three-quarters of a mile. These were the first sustained free flights of powered heavier-than-air machines, and they demonstrated the practicability of mechanical flight. With the advent of the Spanish-American War in 1898, Langley received a $50,000 grant from the U.S. War Department to continue his efforts to achieve manned flight.

Eventually Langley built a full-sized machine driven by a 53-horsepower gasoline engine. He made two well-publicized attempts to fly it in 1903. These flights failed, probably because of defects in the launching device, not because of design or engine malfunction. But Langley was subjected to much public ridicule. Only 9 days after his second disappointment, the Wright brothers made their historic first flight.

A restored and slightly modified version of Langley's airplane was flown successfully by Glenn Curtiss in 1914, and Langley's contributions to flight have been recognized by naming an airfield and an aeronautics laboratory after him.

Langley was a large, reserved man, though witty and charming in private intercourse. He enjoyed a very high scientific reputation and published many scientific articles and reports, as well as popular accounts of his astronomical and aeronautical experiments. He died at Aiken, S. C., on Feb. 2, 1906.

Further Reading

• Langley's writings include The New Astronomy (1888) and Experiments in Aerodynamics (1891; 2d ed. 1901). See also C.M. Manly, Langley Memoir on Mechanical Flight (1911). There are few complete accounts of Langley's life; a useful appreciation of his early achievements is in G. B. Goode, ed., The Smithsonian Institution, 1846-1896 (1897). Bernard Jaffe, Men of Science in America (1944), contains an excellent summary of Langley's work. Langley's life is also dealt with in Charles Doolittle Walcott, Biographical Memoir of Samuel Pierpont Langley (1912), and in Joseph Gordon Vaeth, Langley: Man of Science and Flight (1966). The early history of flight is recorded in Archibald Black, The Story of Flying (1940), and Alvin M. Josephy, Jr., and others, eds., The American Heritage History of Flight (1962).