A. E. Douglass
Encyclopedia
A. E. Douglass (July 5, 1867, Windsor, Vermont
– March 20, 1962, Tucson, Arizona
) was an American
astronomer
. He discovered a correlation between tree rings and the sunspot cycle.
Douglass founded the discipline of dendrochronology
, which is a method of dating wood by analyzing the growth ring pattern. He started his discoveries in this field in 1894 when he was working at the Lowell Observatory
. During this time he was an assistant to Percival Lowell
and William Henry Pickering
, but had a falling-out with them, when his experiments made him doubt the existence of artificial "canals" on Mars
and visible cusps on Venus
Craters
on the Moon
and Mars are named in his honor.
, of the American Museum of Natural History
, organized the Archer M. Huntington Survey. One objective of this survey was to determine temporal arrangement of the American Southwest’s prehistoric ruins. Wissler, who had read about Douglass’s work concerning the relationship between precipitation and tree growth, later contacted Douglass saying:
On June 19, 1914, the curator of the American Museum of Natural History wrote a letter to Douglass expressing his desire to begin archaeological analysis as early as possible (Nash 1999: 23).
In 1916, Douglass began obtaining and analyzing archaeological samples first collected during an expedition to northwest New Mexico by the University of Colorado and the American Museum of Natural History. In April 1918, Wissler asked Douglass whether or not it would be possible to assign relative dates to samples that couldn’t be dated absolutely. Although this information would not associate particular sites with exact years, it would reveal whether or not ruins were constructed within the same time period. On May 22, 1919, Douglass informed Wissler that six specimens from Aztec Ruin, New Mexico were cut down within a two year period, and estimated that samples from Pueblo Bonito in New Mexico were possibly 25 years older than those collected at Aztec Ruin. Upon receiving this news, Wissler was certain that Douglass would make a crucial contribution to archaeology. Douglass continued comparing samples between the two sites and concluded Pueblo Bonito actually predated Aztec Ruin by 40 to 45 years. These findings led to realization that relative dating could be used on many of the other ruins in the Southwest. Although promising steps had been made in solving the mystery of the ruins in the Southwest, in 1920, the American Museum of Natural History discontinued the funding of Douglass’s research. In order to continue his dendroarchaeological research, Douglass would have to find funding elsewhere (Nash 1999: 24-30).
could be a potential source of funding. By May of that year, the idea of a Beam Expedition funded by the National Geographic Society was conceived (Nash 1999: 30-31). Beam Expeditions, funded by the National Geographic Society took place in 1923 and 1928. These expeditions produced a floating chronology of 585 years for Southwestern ruins, and extended Douglass’s Flagstaff chronology of Ponderosa Pine, which was 500 years long in 1914, to A.D. 1260. However, these expeditions failed to bridge the gap that existed between these two chronologies (Fritts 1976: 8).
at the University of Arizona
.
(1944) “Tabulation of Dates for Bluff Ruin” Tree-Ring Bulletin Vol. 9, No. 2
(1941) “Age of Forestdale Ruins Excavated in 1939” Tree-Ring Bulletin Vol. 8, No. 2
(1940) “Tree-Ring Dates from the Forestdale Valley, East-Central Arizona” Tree-Ring Bulletin Vol.7, No. 2
(1921) “Dating Our Prehistoric Ruins: How Growth Rings in Timbers Aid in Establishing the Relative Ages in Ruined Pueblos of the Southwest” Natural History Vol. 21, No. 2
Windsor, Vermont
Windsor is a town in Windsor County, Vermont, United States. The population was 3,756 at the 2000 census.-History:One of the New Hampshire grants, Windsor was chartered as a town on July 6, 1761 by Colonial Governor Benning Wentworth. It was first settled in August 1764 by Captain Steele Smith and...
– March 20, 1962, Tucson, Arizona
Tucson, Arizona
Tucson is a city in and the county seat of Pima County, Arizona, United States. The city is located 118 miles southeast of Phoenix and 60 miles north of the U.S.-Mexico border. The 2010 United States Census puts the city's population at 520,116 with a metropolitan area population at 1,020,200...
) was an American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
. He discovered a correlation between tree rings and the sunspot cycle.
- "Douglass tracked this into past centuries by studying beams from old buildings as well as SequoiasSequoiadendronSequoiadendron giganteum is the sole living species in the genus Sequoiadendron, and one of three species of coniferous trees known as redwoods, classified in the family Cupressaceae in the subfamily Sequoioideae, together with Sequoia sempervirens and...
and other long-lived trees. Noting that tree rings were thinner in dry years, he reported climate effects from solar variationSolar variationSolar variation is the change in the amount of radiation emitted by the Sun and in its spectral distribution over years to millennia. These variations have periodic components, the main one being the approximately 11-year solar cycle . The changes also have aperiodic fluctuations...
s, particularly in connection with the 17th-century dearth of sunspots that HerschelWilliam HerschelSir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
and others had noticed. Other scientists, however, found good reason to doubt that tree rings could reveal anything beyond random regional variations. The value of tree rings for climate study was not solidly established until the 1960s." http://www.aip.org/history/climate/solar.htm
Douglass founded the discipline of dendrochronology
Dendrochronology
Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...
, which is a method of dating wood by analyzing the growth ring pattern. He started his discoveries in this field in 1894 when he was working at the Lowell Observatory
Lowell Observatory
Lowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
. During this time he was an assistant to Percival Lowell
Percival Lowell
Percival Lawrence Lowell was a businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death...
and William Henry Pickering
William Henry Pickering
William Henry Pickering was an American astronomer, brother of Edward Charles Pickering. He was elected a Fellow of the American Academy of Arts and Sciences in 1883.-Work:...
, but had a falling-out with them, when his experiments made him doubt the existence of artificial "canals" on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and visible cusps on Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
Craters
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
on the Moon
Douglass (lunar crater)
Douglass is a lunar crater on the far side of the Moon. It lies to the southwest of the crater Frost and south-southwest of the large walled plain Landau....
and Mars are named in his honor.
Collaboration with the American Museum of Natural History
In 1909, Clark WisslerClark Wissler
Clark Wissler was an American anthropologist.Born near Hagerstown, Indiana, Wissler graduated from Indiana University in 1897. He received his doctorate in psychology from Columbia University in 1901. After Columbia, Wissler left the field of psychology to focus on Anthropology...
, of the American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...
, organized the Archer M. Huntington Survey. One objective of this survey was to determine temporal arrangement of the American Southwest’s prehistoric ruins. Wissler, who had read about Douglass’s work concerning the relationship between precipitation and tree growth, later contacted Douglass saying:
Your work suggests to me a possible help in the archaeological investigation of the Southwest…We do not know how old these ruins are, but I should be glad to have an opinion from you as to whether it might be possible to connect up with your modern and dated trees specimens [with wood specimens] from these [prehistoric] ruins by correlating the curves of growth…I shall be glad to hear from you as to whether you think it is possible for us to secure any chronological data from the examination of this material. (Nash 1999: 23).
On June 19, 1914, the curator of the American Museum of Natural History wrote a letter to Douglass expressing his desire to begin archaeological analysis as early as possible (Nash 1999: 23).
In 1916, Douglass began obtaining and analyzing archaeological samples first collected during an expedition to northwest New Mexico by the University of Colorado and the American Museum of Natural History. In April 1918, Wissler asked Douglass whether or not it would be possible to assign relative dates to samples that couldn’t be dated absolutely. Although this information would not associate particular sites with exact years, it would reveal whether or not ruins were constructed within the same time period. On May 22, 1919, Douglass informed Wissler that six specimens from Aztec Ruin, New Mexico were cut down within a two year period, and estimated that samples from Pueblo Bonito in New Mexico were possibly 25 years older than those collected at Aztec Ruin. Upon receiving this news, Wissler was certain that Douglass would make a crucial contribution to archaeology. Douglass continued comparing samples between the two sites and concluded Pueblo Bonito actually predated Aztec Ruin by 40 to 45 years. These findings led to realization that relative dating could be used on many of the other ruins in the Southwest. Although promising steps had been made in solving the mystery of the ruins in the Southwest, in 1920, the American Museum of Natural History discontinued the funding of Douglass’s research. In order to continue his dendroarchaeological research, Douglass would have to find funding elsewhere (Nash 1999: 24-30).
Beam Expeditions with the National Geographic Society
On January 22, 1922, Douglass was informed that the National Geographic SocietyNational Geographic Society
The National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical...
could be a potential source of funding. By May of that year, the idea of a Beam Expedition funded by the National Geographic Society was conceived (Nash 1999: 30-31). Beam Expeditions, funded by the National Geographic Society took place in 1923 and 1928. These expeditions produced a floating chronology of 585 years for Southwestern ruins, and extended Douglass’s Flagstaff chronology of Ponderosa Pine, which was 500 years long in 1914, to A.D. 1260. However, these expeditions failed to bridge the gap that existed between these two chronologies (Fritts 1976: 8).
Discovery of HH-39
In 1929, Douglass set out on a third Beam Expedition. This expedition explicitly targeted samples that would potentially bridge the gap between the two chronologies. Finally, on June 22, 1929, a beam labeled HH-39 was extracted at the Show Low site in Arizona. This beam took the Flagstaff chronology back to A. D. 1237. Later that day, the inner rings of HH-39 were successfully crossdated against the outer rings of Douglass’s floating chronology. Over 15 years after he began working with Clark Wissler, Douglass had bridged the gap and, as a result, had a continuous record of tree-ring data dating back to A. D. 700. For the first time in history, dates could be assigned to Southwestern ruins with certainty. Cliff dwelling at Tsegi Canyon, Mesa Verde, and Canyon de Chelly dated back to the 13th century. It was determined that Aztec Ruin was constructed during a period ranging from A. D. 1111-A. D. 1120. Pueblo Bonito was found to be built in the latter portion of the 11th century (Fritts 1976: 8).Douglass Publishes his findings in National Geographic
Douglass formally reported his findings in the December 1929 issue of National Geographic. He wrote:
Its inner rings overlapped the late decades of the old chronology by 49 years, the final ring resting on the year 537 of that sequence; its outer ones overlapped the earliest 120 years of the new, the last one reaching to 1380. Thus the 26 years from 1260 to 1286, which belonged to both chronologies, were definitely matched and their union confirmed by HH-39, which in American archaeology is destined to hold a place comparable to Egypt’s Rosetta Stone…With careful archaeological study we shall perhaps be able to trace the movement of clans and test tribal traditions which have been so often quoted as the early history of these people (Douglass 1929: 770).
Emil Haury’s Recollection of the HH-39 Discovery
Emil Haury, one of the men who helped extract HH-39, stated:
For the three of us [Emil W. Haury, Lyndon L. Hargrave, and Neil M. Judd], the experience was unforgettable. To be present at the instance of the celebrated breakthrough in science that set the chronological house in order for the Southwestern United States was reward enough. But beyond that, was the privilege to work for a time at the side of Douglass, the scholar, the astronomer turned archaeologist (Haury 1962: 14).
Douglass formalizes Tree-Ring Science
Douglass returned to the University of Arizona where he became the first person to formally teach classes in dendrochronology. In 1937, the science continued to develop when Douglass established the Laboratory of Tree-Ring ResearchLaboratory of Tree-Ring Research
The Laboratory of Tree-Ring Research was established in 1937 by A.E. Douglass, founder of the modern science of dendrochronology. The LTRR is a research unit in the College of Science at the University of Arizona in Tucson, Arizona...
at the University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
.
Applications of Douglass’s Work
Since Douglass’s famous discovery in the American Southwest, his dendroarchaeological techniques have been used to date structures around the world. Furthermore, dendrochronology has been applied in a number of ways. Currently, tree rings are being used to reconstruct an array of activity including: fire regimes, volcanic activity, hurricane activity, glacial movement, precipitation, mass movements, and hydrology. In many ways anthropologists, ecologists, geographers, and geologists are able to analyze the past and predict future trends. All of this is possible thanks to the archaeological achievement of A.E. Douglass.Selected works
Douglass, A.E.(1944) “Tabulation of Dates for Bluff Ruin” Tree-Ring Bulletin Vol. 9, No. 2
(1941) “Age of Forestdale Ruins Excavated in 1939” Tree-Ring Bulletin Vol. 8, No. 2
(1940) “Tree-Ring Dates from the Forestdale Valley, East-Central Arizona” Tree-Ring Bulletin Vol.7, No. 2
(1921) “Dating Our Prehistoric Ruins: How Growth Rings in Timbers Aid in Establishing the Relative Ages in Ruined Pueblos of the Southwest” Natural History Vol. 21, No. 2
External links
- A.E. Douglass: Short biography from the Lowell ObservatoryLowell ObservatoryLowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
. - American Museum of Natural History
- Laboratory of Tree-Ring Research at the University of Arizona