TITLE:  Langley, Samuel Pierpont



Born:  1834 August 22, Roxbury, Mass.(suburb of Boston)

Died:  1906 February 27, Aiken, S.C.; buried at Forest Hill Cemetery, Boston.



Father:  Samuel Langley, wholesale merchant in Boston.

Mother:  Mary Sumner Williams

Genealogy: Ancestors primarily English, plus a little Welsh; most immigrated to Massachusetts in beginning of the Seventeenth Century. He is descended from many men prominent in the history of Massachusetts including the Mathers(Richard, Increase, and Cotton) and Rev. John Cotton. Increase Mather, who served as President of Harvard College, published a paper on comets in 1683; this is believed to be the first research published on Astronomy in America.

Married:  Never married.

Children:  No children. Although he loved children and had a special Children’s Room installed at the Smithsonian Institution; above the entrance it read, “Knowledge Begins in Wonder.”

Education:  Several private schools, Boston Latin School, and Boston High School(graduated 1851).

Honors:           Third Secretary of the Smithsonian Institution—considered the greatest

scientific appointment in the United States, at that time(1887).

                        President of the American Association for the Advancement of Science(1888)

                        International unit of radiant energy named the langley(1947)

Henry Draper Gold Medal of the National Academy of Sciences

                        Rumford Gold and Silver Medals of the American Academy of Arts and Sciences

                        Janssen Medal of the Institute of France

                        Rumford Medal of the Royal Society of London

                        National Academy of Sciences(member)

                        Institute of France(correspondent)

                        Royal Society of London(foreign member)

                        Royal Society of Edinburgh(foreign member)

                        Academia dei Lincei of Rome(foreign member)

Honorary Degrees:

                        Oxford University, D.C.L.

                        Cambridge University, D.Sc.

                        Harvard University, LL.D.

                        Princeton University, LL.D.

                        University of Michigan, LL.D.

                        University of Wisconsin, LL.D.

Major Publications:   Book: Langley, S.P.. The New Astronomy. Boston: Ticknor, 1888.

“Minute Structure of the Solar Photosphere.” American Journal of Science and Arts 1874 February.

“The Bolometer and Radiant Energy.” Proceedings of the American Academy of Arts and Sciences XVI (1881).

“The Selective Absorption of Solar Energy.” American Journal of Science 1883 March.

“Experimental Determination of Wavelengths in the Invisible Prismatic Spectrum.” Ibid. 1884 March

“Researches on Solar Heat and its Absorption by the Earth’s Atmosphere: A Report on the Mount Whitney Expedition.” Professional Papers of the Signal Service XV 1884.

“The New Astronomy.” Century Magazine 1884-1885.

“On the Temperature of the Surface of the Moon.” Memoirs of the National Academy of Sciences III Pt.1 1885.

“Observations on Invisible Heat Spectra and the Recognition of Hitherto Unmeasured Wavelengths.” Proceedings of the American Association for the Advancement of Science 1885 and American Journal of Science and Arts 1886 January.

“On Hitherto Unrecognized Wavelengths.” London, Edinburgh and Dublin Philosophical Magazine 1886 August and American Journal of Science and Arts 1886 August.

“The Temperature of the Moon.” Memoirs of the National Academy of Sciences IV Pt.2 1889.

“Energy and Vision.” American Journal of Science and Arts 1888 November.

Annals of the Astrophysical Observatory of the Smithsonian Institution I (1900).

“The Solar Constant and Related Matters.” Astrophysical Journal 1903 March.


Brief Biography:


            Samuel Pierpont Langley had an interest in Astronomy beginning in his youth, using a small telescope owned by his father. He, at age 20, and his only brother John W. Langley(seven years younger than Langley, who became a professor of Chemistry), started building small telescopes. Later on, they built a six-inch reflecting telescope from scratch, refusing to buy any finished parts as this would take away from the challenge. Due to young Samuel’s perfectionist streak, it was a long and tedious task—and, it was rebuilt more than once until Langley was finally satisfied with the result. After three years, Langley finally had an instrument capable of professional scientific observations.


His parents instilled an interest in reading in their children, and young Samuel was a frequent visitor to the Boston Public Library. Langley was very mechanically inclined, and he continued his interest in Astronomy as he neared high school graduation. However, with few employment opportunities in Astronomy, he was undecided about a career choice. Finally, he decided to become an architect or civil engineer. Yet, instead of attending college, after high school graduation, he decided to go to work immediately to learn these crafts.


            Langley worked, for awhile, in an architectural firm in Boston; then, he obtained similar work in St. Louis, then in Chicago. Through this experience, he developed superb mechanical and free-hand drawing skills, a well as learning sound business procedures.


But he became disinterested in architecture and returned home in 1864. His brother had just been discharged from the Union Navy, after three years in the Civil War; apparently, Langley did not take part in the Civil War. In 1865, the Langley brothers toured the museums, historic sites, and centers of culture and learning in Europe; of course, this included many of Europe’s observatories.


            On his return to America, Langley learned that the Harvard College Observatory, in nearby Cambridge, Massachusetts, was expanding. Impressed with Langley’s enthusiasm and experience in telescope construction, Observatory Director, Professor Joseph Winlock hired him as an observatory assistant. Langley’s chosen career had begun!


            However, Langley stayed at Harvard less than a year. In 1866, he was offered the position of Professor of Mathematics at the U.S. Naval Academy in Annapolis, Maryland, with the understanding that his primary duty would be to restore to operation the Academy’s small astronomical observatory, This observatory had been unused for several years, while the Naval Academy spent the Civil War years in the safer location of Newport, Rhode Island.


            At the invitation of Western University of Pennsylvania Trustee William Thaw, a wealthy Pittsburgh philanthropist, Langley agreed to take charge of the University’s newly-acquired Allegheny Observatory as Professor of Astronomy and Physics in 1867. Thaw and two other wealthy Pennsylvanians had conceived the Allegheny Observatory in 1859, shortly after the passing Donati’s Comet. After hoping to purchase an eight-inch refractor telescope for the observatory, the Allegheny Observatory actually opened on 1861 November 27 with a 13-inch Fitz refractor telescope—third largest in the world(15-inch refractors existed at Harvard and in Russia)!


            In the first years, Allegheny Observatory was used strictly for the entertainment of the members of the Allegheny Telescope Association. As interest in the Observatory waned, resulting in loss of club members, the Observatory went into debt. In May of 1867, the club voted to donate the Observatory to the Western University of Pennsylvania. This legal conveyance did occur through an act of the Pennsylvania General Assembly, but only after Thaw and others eliminated the Observatory’s debt.


            Langley’s primary research at Allegheny, discussed in the section “Astronomical Contribution and Significance,” was of the Sun and the effect of solar radiation on the Earth’s atmosphere. He also helped fund his research by selling time to the railroads and others and started his research on aerodynamics, also discussed below.


            Langley was appointed Assistant Secretary of the Smithsonian Institution on 1887 January 12. After Smithsonian Secretary Spencer F. Baird, a famed naturalist, died later that year, Langley was appointed the third Secretary of the Institution on 1887 November 18—at that time, the greatest scientific appointment in America. When Langley first came to the Smithsonian, arrangements had been made that he could retain the Directorship of the Allegheny Observatory(without pay) to continue his solar and aerodynamic research; half of his time was spent in Washington and half at Allegheny. This arrangement continued until 1891, when Langley’s former assistant, James E. Keeler, became Director of the Allegheny Observatory.


            Langley continued as Secretary of the Smithsonian Institution until his death in February of 1906. He suffered a paralytic stroke on 1905 November 22. He convalesced, with the assistance of a faithful nurse and his beloved niece, in Aiken, South Carolina. It seemed that, with Langley’s strong constitution, he would recover. However, he suffered a second stroke on 1906 February 25; he died two days later at the age of 71 and one-half years.


            Langley’s funeral was held at All Souls Church in Downtown Washington, D.C. on 1906 March 2. The eulogy was delivered by Chaplain of the Senate, Edward Everett Hale, a Unitarian minister best known for his short story, The Man Without a Country. Pall bearers included the Chief Justice of the United States and the Vice President of the United States. The newspapers, which had ridiculed his manned flying machine just a little more than two years earlier, now praised his legacy.


            The afternoon of the following day, Langley was laid to rest in Forest Hill Cemetery in Boston.


            Further biographical information can be read in the following section on “Astronomical Contribution and Significance.”




1)      Solar Research


Langley’s chief study was the Sun and solar radiation, which he explained, “We are all its products,” as well as the central controlling body of the Solar System. And, he added only half-jokingly, “it is perhaps the only celestial object that I can hope to see and observe in any detail and with any regularity in the Pittsburgh area with its coal-burning steel mills and its soot- and smoke-filled atmosphere.”


Through his researches, he developed, what he termed, the New Astronomy. The old Astronomy was observational and concentrated on position of celestial objects. The New Astronomy concentrated on measuring the celestial bodies and analyzing their physical composition, structure, and other properties. It took a few years, but with Langley’s successful research, the New Astronomy was finally accepted as a new branch of Science, now known as Astrophysics.


Langley’s greatest astronomical achievement was in measuring the distribution of heat in the spectrum of the Sun. Yet, the instruments of his day were not of the precision needed for reliable data. So, Langley invented the bolometer in December of 1880, used to detect radiant energy(i.e. heat) from celestial bodies, to an accuracy of one-hundred-thousandth of a degree Celsius. A bolometer electrically measures a slight difference in resistance between two thin, blackened strips of tape, when one strip receives radiation while the other does not; the difference indicates the amount of radiation received. With the bolometer, Langley extended the spectrum beyond what Sir Isaac Newton would have dreamed possible.


Langley spent years studying the selective absorption of solar radiation by the Earth’s atmosphere. Up until 1881, this study had been limited to the relatively low altitudes of Pennsylvania. Then, with funding from Pittsburgh philanthropist William Thaw and the U.S. Army Signal Service(responsible for much of the weather forecasting of that era), Langley led an expedition to Mount Whitney in the Sierra Nevada mountain range of California; at 14,494 feet, this is the highest point in the continental United States.


In returning to Allegheny, Langley had notebooks full of instrument readings, observations, and other information; it took two years to analyze this data. The result was a 240-page technical report, “Researches on Solar Heat and its Absorption by the Earth’s Atmosphere: A Report on the Mount Whitney Expedition,” published by the U.S. Signal Service in 1884.


Although his measurements at the mountain summit were quite limited, due to weather conditions, good readings were acquired from the lower “Mountain Camp,” which was still two miles above sea level. From this expedition, much was learned about solar radiation and its behavior within the Earth’s atmosphere.


Using data from the Mount Whitney expedition, Langley attempted to set the Solar Constant, the heat value of solar radiation striking the top of the Earth’s atmosphere. He judged the Solar Constant to be three calories per square centimeter per minute; unlike the commonly known “calorie”(which, scientifically, is really a kilocalorie), a scientific calorie is the amount of heat required to raise one gram of water through one degree Celsius.


Although three calories was a fair estimate, it was incorrect; he miscalculated the absorption of the Sun’s energy by the air. Although the reductions of his own data were in error(had these reductions been more accurate, he would have been much closer to the true figure), this value of the Solar Constant was accepted by scientists for about twenty years, due to Langley’s reputation in Solar Physics. With satellite data, we now know the value of the Solar Constant to be about two calories; about 23 percent of solar radiation is absorbed by the atmosphere and does not reach the Earth’s surface.


During the Mount Whitney expedition, Langley discovered a previously unobserved and unknown extension of the infrared region of the spectrum. With his ability to, again, find this infrared region back at Allegheny Observatory, he was able to start mapping this new region of the spectrum.


He used the bolometer to obtain a good approximation of the temperature of the Moon. And, he became fascinated with light from a firefly, when the bolometer could detect no heat. No practical way was found to harness the firefly’s illumination for human use, and the invention of the electric light bulb ended such research.


Langley attended several solar eclipses, to study the Sun’s corona. And, his classic 1873 illustration of a sunspot became standard in Astronomy textbooks of the time. Ironically, as a perfectionist, Langley readily admitted shortcomings of the drawing.


Langley believed in popularizing Astronomy and Science, writing in 1877, “Science is not for the professional student alone. Everyone will take an interest in the results if they are only put before the world in the right way.” Langley did this by contributing occasional items to the Pittsburgh Gazette and lecturing throughout the Pittsburgh area.


In honor of Langley’s research accomplishments in the field of Solar Physics, the international unit of radiant energy was named the langley, in 1947. The langley is equivalent to “one gram calorie per square centimeter.”


2)      Establishment of the Smithsonian Astrophysical Observatory in Washington


After Langley became Secretary of the Smithsonian Institution, he founded the Smithsonian Astrophysical Observatory in the Spring of 1890. However, with minimal assistance from the U.S. Congress, this Observatory lacked sufficient facilities for many years. As he did at Allegheny, Langley was able to make-do, and he eventually turned the Astrophysical Observatory into a valuable research facility. It was not until 1955 that an adequate observatory was made available, for the Smithsonian, in Cambridge, Massachusetts.


During his Smithsonian tenure, he also established the Regional Bureau of the United States of the International Catalogue of Scientific Literature.


3)      Standard Time Zones and Revenue for Research:

Providing Time to the Railroads


An obituary in the 1906 March issue of National Geographic magazine credits Langley as the “first astronomer to succeed in making money for the public out of his profession.” To help fund his research, he found a way that the Allegheny Observatory could generate revenue, as the Western University of Pennsylvania(now the University of Pittsburgh) was not well-endowed at this time. Langley’s revenue generator also helped place the United States, and then the world, into standard time zones!


In essence, he sold time. At that time, every city and major town set their own time by the Sun; hence, the time would be different when one traveled from one city to another. As the railroads were rapidly providing a unified transportation system, this system of a different time in every city was completely unworkable. Not only did it make railroad schedules almost useless, there was a continual danger that two trains could collide as many areas were served with but a single railroad track.


In 1869, Langley obtained a transit telescope to determine the exact time by the stars, and he assembled a special telegraph system connected to his master clock. He solved the problems of the railroads by creating his own precise time, known as the “Allegheny System,” which he transmitted to the railroads, twice daily, over the telegraph. Although he had originally designed the system to provide time to the City clocks of Allegheny City and Pittsburgh, his railroad customers became much more important.


The Allegheny System provided time to thousands of miles of railroad(including more than 300 railroad stations of the Pennsylvania Railroad), in the middle-west and southern regions of the United States; in all, 42 railroads subscribed to this service. Jewelers and other businesses also found a time subscription to be valuable. Within the first four years, the time service brought in $60,000 which helped pay for the Observatory’s research and the purchase of instruments; originally, the University’s trustees had thought that Langley’s $2,000 a year salary would be the Observatory’s largest expense. The City of Pittsburgh continued paying $1,000 a year for the time service up until 1923; in this year, the National Bureau of Standards started providing time, free-of-charge, through their new shortwave radio station, WWV.


Langley’s time service also inspired the eventual time zone system we have today. With the Allegheny System as an example, Charles Ferdinand Dowd(principal of a young ladies’ seminary in Saratoga, N.Y.) and Sandford Fleming(great engineer who built the Canadian Pacific Railroad) started lobbying and promoting a time zone system. Consequently, the great railroad conference of 1883 set-up four American time zones; this idea was accepted internationally in 1884.


4)      Research into Aerodynamics


Langley is also a very important pioneer of flight and research into aerodynamics. Until his investigations, research on flight had been restricted to amateurs, with the possible exception of Leonardo da Vinci. Langley was the first person to explore aerodynamics employing the rigorous scientific method.


Thus, his researches were really the beginning of a new technology that led to a revolution in transportation, and eventually allowing scientific research in the upper reaches of the atmosphere including astronomical research. Although it was for later pioneers, such as Robert Goddard, to work on systems capable of going beyond our atmosphere, Langley’s research was certainly a first step toward freeing man from the bonds of Earth’s gravitational field.


An 1886 conference in Buffalo, of the American Association for the Advancement of Science, rekindled Langley’s boyhood interest in aerodynamics and the problems of flight. Langley’s first order to John A. Brashear, the well-known Pittsburgh producer of fine optics and scientific apparatus, for construction of an airplane model, came on 1887 March 8. Langley’s greatest successes came in 1896, when two “aerodromes” were catapulted from a houseboat on the Potomac River for flights of 3,000 feet and 4,200 feet. Although both were unmanned vehicles, they were the first sustained free flights of power-propelled heavier-than-air machines.


In the 1897 June issue of McClure’s Magazine, Langley stated: “I have brought to a close the portion of the work which seemed to be specially mine—the demonstration of the practicability of mechanical flight—and, for the next stage, which is the commercial and practical development of the idea, it is probable that the world may look to others.”


However, particularly with the outbreak of the Spanish-American War, the U.S. War Department was very interested in a man-carrying airplane. The Government provided $50,000 to Langley, to develop this new war machine. As with most defense contracts, Langley was obliged to do his research in secret; the newspapers of the day, skeptical of the powered flight of a man, were very unhappy that they could not view Langley’s preliminary tests.  Finally, when two test flights were observed by the media(October 8 and December 8 of 1903), both ended in failure, due to defects in the launching device. Newspaper ridicule, failing health(Langley was now age 69), and the depletion of the War Department grant brought an end to Langley’s aerodynamics research. Nine days after Langley’s last attempt, the Wright Brothers made their historic first manned flight in North Carolina.


5)    Other Achievements


In 1890, Langley established the National Zoological Park in Washington. He was concerned that, up until this time, zoology was being studied primarily with hides, skins, and skeletons of dead animals. He felt that such research should include observations of animals in their natural habitat. Hence, for both researchers and the general public, he felt there should be a National Zoo in Washington, where wild animals would be permitted to live in natural surroundings, as far as feasible.


During his Smithsonian tenure, he also launched the National Gallery of Art and broke ground for National History Building of the National Museum.




Vaeth, J. Gordon. Langley, Man of Science and Flight. New York: Ronald Press Co., 1966.


Langley, S.P.. The New Astronomy. Boston: Ticknor, 1888.


Obendorf, Donald Leroy. Samuel P. Langley: Solar Scientist, 1867-1891. 1969.


Beardsley, Wallace R. Samuel Pierpont Langley: His Early Academic Years at the Western University of Pennsylvania. 1978.


Brashear, John A., Edited by W. Lucian Scaife. John A. Brashear, Autobiography of A Man Who Loved the Stars. Boston: Houghton Mifflin Company, 1925


Starrett, Agnes Lynch. Through One Hundred and Fifty Years. Pittsburgh: University of Pittsburgh Press, 1937.(History of the University of Pittsburgh)


Alberts, Robert C. Pitt: The Story of the University of Pittsburgh 1787-1987. Pittsburgh: University of Pittsburgh Press, 1986.


Malone, Dumas, Ed. Dictionary of American Biography. New York: Charles Scribner’s Sons, 1961.


Langley, S.P. Samuel Pierpont Langley's Writing on Radiant Energy.
Excerpts from: Langley, Samuel Pierpont, 1889: The New Astronomy, Houghton, Miffline & Company, Boston & New York, pp. 71-78.
< http://eosweb.larc.nasa.gov/EDDOCS/Radiant_Energy.html > (2001 August 2; updated link and web page: 2010 Jan. 21)


Brashear, J.A. "Biographical Sketch of S. P. Langley." Popular Astronomy. XIV, 1906.

(Part of "Bridging the Urban Landscape" by The Carnegie Library of Pittsburgh)

< http://www.clpgh.org/exhibit/neighborhoods/northside/nor_n112.html > (2001 July 27)

Other Internet Biographies of Samuel Pierpont Langley:

Link 1 *** Link 2 *** Link 3 *** Link 4 *** Link 5 *** Link 6 *** Link 7 *** Link 8 *** Link 9 *** Link 10

Walsh, Glenn A. "Pittsburgh's Allegheny Observatory: New History Film." Blog Posting.
SpaceWatchtower 2012 April 19.
New film documentary regarding the largest astronomical observatory located within the city limits of a major American city. Henry Clay Frick and Andrew Carnegie helped John Brashear construct the new Allegheny Observatory building. Samuel Pierpont Langley, James E. Keeler, and John Brashear were Directors of the original Allegheny Observatory.


Biographies of John A. Brashear * James E. Keeler *** Other Internet Biographies

News Regarding Samuel Pierpont Langley

Benningfield, Damond. "Visiting Astronomers" Radio Feature.
StarDate Radio Program, University of Texas McDonald Observatory 2018 July 22.
One of the few on the list is Mount Langley, a 14,000-foot summit in California. It’s named for Samuel Pierpont Langley, who was a long-time director of the Allegheny Observatory.

Chute, Eleanor. "Langley ready to take a new shape, Former West End high school will now host K-8."
Pittsburgh Post-Gazette 2012 Aug. 27.

Lowry, Patricia. "Places: Bring an open mind to open house at the Brashears' Perry Hilltop home."
Pittsburgh Post-Gazette 2008 Nov. 28.
Also talks about home's proximity to the original Allegheny Observatory run by S.P. Langley, and where Professor Langley did early experiments in heavier-than-air flight.

Krift, F.A. "City councilman to thank for daylight saving time."
Pittsburgh Tribune-Review 2008 Nov. 2.
While Samuel Pierpont Langley was responsible for promoting national time zones, another Pittsburgh-area resident, Pittsburgh City Councilman Robert Garland, is responsible for pushing-through Benjamin Franklin's dream of Daylight Saving Time in the Summer months.

Zapf, Karen. "Langley's passion for flight began at Allegheny Observatory."
Pittsburgh Tribune-Review 2008 Oct. 26.

Declaring Saturday, October 11, 2008 "Langley High School Day." Proclamation.
Pittsburgh City Council 2008 Oct. 14.
Related Information

Congratulating Langley High School Alumni Association on Tenth Anniversary. Proclamation.
Pittsburgh City Council 2008 Oct. 14.
Related Information

Langley High School, opened in Pittsburgh in April of 1923, was named for
Western University of Pennsylvania (now the University of Pittsburgh)
Astronomy Professor Samuel Pierpont Langley who directed the original
Allegheny Observatory for 25 years.


Glenn A. Walsh, free-lance writer and Internet web page designer. Former Planetarium Lecturer and Astronomical Observatory Coordinator, Buhl Planetarium and Institute of Popular Science, Pittsburgh. Former Treasurer and Trustee, Andrew Carnegie Free Library and Music Hall, Carnegie, Pa. The author can be contacted by electronic mail:

< gawalsh@planetarium.cc >.


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