Historian Finds Treasure in Douglass' Cycloscope at Arizona State Museum

UA News Services
June 13, 2003

A science historian has discovered how a famous early University of Arizona scientist used his amazing contraption called the "cycloscope" in a long but futile quest to discover predictable cycles of solar activity in tree rings.

Andrew Ellicott Douglass (1867 ? 1962) "was a polymath of the first order, engaged in astronomy, physics, botany, climatology, photography and archaeology," said Shaw D. Kinsley. "Douglass made a substantial contribution to American science and designed some extraordinary instruments."

Three years ago Kinsley earned a master's degree in the history of science from Oxford University, where he studied science instruments dating from 1470 to 1930.

"My interest in instruments centers more on the 16th and 17th centuries, but there simply aren't very many artifacts from that period floating around in Arizona," said Kinsley, who works at the UA Center for Creative Photography until the end of June. Kinsley also is knowledgeable about the photographic equipment that John Wesley Powell used on his 1871 journey down the Colorado River.

Kinsley said Arizona State Museum conservator Nancy Odegaard tipped him off to Douglass' "dendrochronology unit" stored at the state museum.

The apparatus, a far bigger device than any of its predecessors, features an "Illuminator-Comparator" ? an attachment that shines light through displays of tree-ring-width skeleton plots and cyclograms of sunspot numbers -- two mirrors that move along a track that extends to 40 feet, and sophisticated optics on a two-tier analyzing bench, Kinsley discovered.

A lightbox of ten, 60-watt light bulbs spaced 4 inches apart illuminates the display plots, shining the subsequent light patterns onto the mirrors along the moveable track. The mirrors reflect light into the optics so that observers can immediately see when plots match and when they don't. A wheel on the track measures how far the mirrors are from the optics, which tells the length, in years, of a pattern's cycle.

Kinsley reviewed 180 boxes of Douglass' material archived at the museum and at UA Special Collections for the history of the cycloscope. He also found film footage of Douglass, assisted by Edmund Schulman, demonstrating the cycloscope.

Last September, Kinsley reported on Douglass' complex invention at the 21st Scientific Instrument Symposium in Athens, Greece, and at the Antique Telescope Society Convention at Trinity College, Dublin, Ireland. He recently gave an informal talk about it at the UA Laboratory of Tree-Ring Research.

"Douglass began developing the cycloscope in 1913," he said. "He designed this particular instrument in 1935, had Stanford University build it in 1936, and named it the Merriam Cycloscope in honor of the then-president of the Carnegie Institution of Washington, which funded the project. This model is the most complete and efficient version of Douglass' cycloscopes," Kinsley said.

Douglass, first director of the Lowell Observatory in Flagstaff and later founder of the UA Steward Observatory in Tucson, began studying tree-rings for information on climate before he joined the UA faculty in 1906. Douglass' greatest technical discovery, made in 1911, was the technique of crossdating tree rings, or matching ring patterns to extend the record of precise tree ages back through time. This achievement earned Douglass' reputation as the "father of dendrochronology."

By 1909, Douglass published tree-ring research results that he said suggested a close relationship between climate and the 11.3-year sunspot cycle. Douglass searched for evidence that would confirm this idea for the rest of his life.

"There is some correlation, but it's not strong enough to actually bet on," Kinsley said.

Douglass' use of the cycloscope for tree-ring analysis aimed at climate prediction keenly interested the federal government during World War II, Kinsley noted.

University of Tennessee historian George Webb details that story in a biography of Douglass, "Tree Rings and Telescopes" (University of Arizona Press, 1983).

The Los Angeles Bureau of Power and Light, which managed Boulder Dam, in 1941 recruited Douglass to collect tree-ring data needed for 5-to-10-year predictions of Colorado River watershed runoff. The bureau wanted to deplete reservoir water for increased hydroelectric power production as a means to step up defense-related magnesium production in southern California. Schulman and other tree-ring scientists collected hundreds of tree samples from New Mexico, Colorado, Utah and Wyoming for the project, and Douglass analyzed much of the data with the cycloscope.

If Douglass were alive today, he might apply for funds for his defense-related climate research from the Homeland Security Program.