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Langley, Samuel Pierpontlocked

(22 August 1834–27 February 1906)
  • Tom D. Crouch

Samuel Pierpont Langley. 1903.

Right, with Charles M. Manly on the houseboat which served to launch Langley's Aerodrome.

Courtesy of NASA (LaRCL-1990-04340/GPN-2000-001298).

Langley, Samuel Pierpont (22 August 1834–27 February 1906), astrophysicist and aviation experimenter, was born in Roxbury, Massachusetts, the son of Samuel Langley, a wholesale merchant and banker, and Mary Sumner Williams. Langley attended the Boston Latin School and graduated from the Boston High School in 1851. He spent the years 1851–1857 preparing for a career in civil engineering and architecture and worked as a draftsman and merchant in Chicago and St. Louis from 1857 to 1864.

Langley regarded his years in the West as a false start in life. He returned to Boston early in 1864 to seek a career in astronomy, a subject that had fascinated him since childhood. Together with his brother, John Williams Langley, a former medical officer in the Union navy, Samuel embarked on a grand tour of European observatories and laboratories. Joseph Winlock, a leading American astronomer and family friend, hired Langley as an assistant at the Harvard Observatory on Langley’s return from Europe. In 1866 Langley was appointed assistant professor of mathematics with responsibility for reestablishing the U.S. Naval Academy observatory. In 1867 he moved to the Western University of Pennsylvania (now the University of Pittsburgh), where he became professor of physics and astronomy and director of the Allegheny Observatory.

Langley remained at Pittsburgh for twenty years, building a reputation as a pioneer in astrophysics—the “new astronomy”—and establishing himself as a leading American administrator of science. Searching for sources of income for the observatory, he devised a method of distributing precise standard-time signals to railroads, cities, and other interested customers. He also attracted the support of private benefactors, notably William Thaw.

In November 1886 Spencer Fullerton Baird, secretary of the Smithsonian Institution, offered Langley an appointment as assistant secretary in charge of international exchanges, the library, and publications. Langley accepted, explaining to friends that Pittsburgh no longer provided “the companionship that a student of science wants.” He became secretary of the institution after Baird’s death in 1887.

As secretary, Langley worked to extend the scientific interests of the Smithsonian and to expand its museum and public educational functions. His major administrative accomplishments were the establishment of both the Smithsonian Astrophysical Observatory and the National Zoo. He also played a key role in negotiations leading to the creation of the Freer Gallery of Art.

As an astrophysicist, Langley took little interest in the traditional astronomy of position. He had no taste for the complex mathematical procedures required to reduce observational data and recognized that his own talents lay in the area of instrument design and experimentation. He was particularly interested in the impact of solar radiation on the earth. His chief goal was to arrive at a figure for the “solar constant,” a measure of the intensity of solar energy at the earth’s mean distance from the sun. The key to his work was the bolometer, an instrument he invented in 1878. Essentially an electrical thermometer, the device employed a thin strip of metallic tape to register differences in temperature as small as one millionth of a degree. Langley coupled his instrument with a spectrograph and began to study temperature distributions across the solar spectrum.

In an attempt to determine the extent to which the atmosphere filtered solar radiation, Langley organized an expedition to Mount Whitney, California, in 1881. With the assistance and support of the War Department, the Pennsylvania Railroad, and his longtime friend William Thaw, Langley established several temporary observing stations on the peak. In the thin, clear mountain air, he and his principal assistant, James Keeler, obtained bolometric readings to compare with the Pittsburgh data and extended their measurements into the far infrared region of the spectrum for the first time.

Langley continued his bolometric studies in Pittsburgh and at the Smithsonian Astrophysical Observatory, which he established in 1890. His interest in solar energy shaped the Smithsonian research agenda in astrophysics for the next two generations. Ironically, in view of the fact that he was a meticulous experimenter and observer, Langley overestimated the value of the solar constant by one-third on the basis of flawed theoretical assumptions. His experimental data was nevertheless of real value to astronomers and physical scientists.

Langley also played an important role as a popularizer. A gifted writer, he published articles on his expeditions in the National Geographic and introduced general readers to the latest ideas in astronomy in a series of articles for Century Magazine and in his popular book The New Astronomy (1888).

A lifelong bachelor, Langley was nonetheless very fond of children and was committed to museum education. He was personally involved in the creation of the Children’s Room exhibition in the Smithsonian Castle, complete with carefully crafted labels and low cases designed for viewing by youngsters.

Langley is best remembered as an aviation pioneer. A childhood interest in the subject was reawakened by a discussion of the flying machine problem at an 1886 meeting of the American Association for the Advancement of Science. Within a year he had begun experiments with a whirling arm and other engineering test equipment designed to establish the physical requirements for flight. His report, Experiments in Aerodynamics (1891), concluded that “mechanical flight is possible with engines we now possess.”

Even before he had published his related study, The Internal Work of the Wind (1893), Langley had begun to apply the data he had gathered to the design of actual flying machines. His first aircraft were small models powered by twisted rubber strands driving propellers. By the fall of 1891, he was planning much larger models, with wingspans of up to fourteen feet, that would be powered by lightweight steam engines.

As secretary of the Smithsonian, Langley poured a great deal of time and money into the design and construction of his powered models. He first tasted success on 6 May 1896, when Smithsonian workmen catapulted Aerodrome No. 5 into the air from the roof of a houseboat anchored in the Potomac River. The craft completed two successful flights that day, covering distances of up to 3,300 feet. Other successful flights with this and similar models followed between 1896 and 1902.

In 1898 the U.S. Army Board of Ordnance and Fortification presented Langley with a $50,000 grant to develop a full-sized aerodrome capable of flight with a pilot on board. The airframe of the large machine was patterned after the small aerodromes flown in 1896. Charles Matthews Manly, Langley’s chief aeronautical assistant, transformed a less than satisfactory internal combustion rotary engine developed by Stephen Balzer into a radial power plant weighing 200 pounds and developing 50 horsepower.

Like its small predecessors, the Great Aerodrome was designed to be catapulted into the air from the roof of a houseboat. Two unsuccessful attempts were made to launch the craft with Manly as test pilot. On 7 October 1903 the machine shot down the launch rail and fell into the Potomac. One Washington reporter commented that the Great Aerodrome seemed to have the flying qualities of “a handful of mortar.” The second attempt to launch the aerodrome took place on 8 December 1903. This time the rear wings failed as the craft was racing down the launch rail. It nosed straight up into the air and flipped into the water on its back. The Great Aerodrome was destroyed, but Manly escaped with his life.

The failure of the Great Aerodrome exposed Langley to considerable criticism in the press and on the floor of Congress. Representative Gilbert Hitchcock of Nebraska summed up the attitude of the critics in a comment to a reporter from the Brooklyn Eagle, “You can tell Langley for me … that the only thing he ever made fly was government money.” To the end of his life, Langley remained convinced that the Great Aerodrome had not received a fair trial. “Failure in the aerodrome itself or its engines there has been none,” he commented in the Annual Report of the Board of Regents of the Smithsonian Institution, 1904. The aerodrome, he wrote, “is at the moment of success, and … a lack of means has prevented the continuance of the work.” Later Smithsonian claims that the Great Aerodrome had been “capable of flight” led to a long and bitter controversy with Orville Wright. Subsequent investigations have demonstrated beyond any reasonable doubt that the structure of the machine was too weak to have withstood the forces that would be imposed on it in flight. Moreover, the control system was inadequate.

Discouraged by the failure of the Great Aerodrome, and stung by the criticism leveled at him, Langley suffered yet another disappointment when a trusted Smithsonian employee was discovered to have stolen a large sum of money from the institution. Langley died at Aiken, South Carolina, after a series of strokes.


The official papers of Samuel Langley are held by the Smithsonian Institution Archive, which also holds a microform copy of all Langley manuscript material in the collections of the University of Pittsburgh. “Samuel Pierpont Langley Memorial Meeting,” Smithsonian Miscellaneous Collections 49, no. 4 (1907): 1–47, includes the best available bibliographic guide to Langley’s scientific papers and popular articles. Langley provided a general introduction to his own work in The New Astronomy (1888). He provided a popular description of his early aeronautical successes in “The Flying Machine,” McClure’s Magazine, June 1897, pp. 647–60. C. M. Manly, Langley Memoir on Mechanical Flight, Smithsonian Contributions to Knowledge, vol. 27 (1911), includes detailed information on all the Langley aerodromes. J. Gordon Vaeth, Samuel Pierpont Langley (1966), is a popular biographical treatment. Tom D. Crouch, A Dream of Wings: Americans and the Airplane, 1875–1905 (1981), provides an analysis of Langley’s work in aeronautics and his impact on other experimenters. Cyrus Adler, I Have Considered the Days (1941), includes personal insights into Langley’s character by a close friend.

Much useful biographical information is also to be found in a series of important memoirs published after Langley’s death. The best of these are [G. Brown Goode], The Smithsonian Institution, 1846–1896 (1896); Cyrus Adler, “Samuel Pierpont Langley,” Annual Report of the Smithsonian Institution, 1906; C. G. Abbot, “Samuel Pierpont Langley,” Astrophysical Journal, May 1906; and C. D. Walcott, “Samuel Pierpont Langley,” National Academy of Sciences, Biographical Memoirs 7 (1913): 247–68.