Press Release

Historian Finds Treasure un Douglass’ Cycloscope at Arizona State Museum

By SpaceRef Editor
June 16, 2003
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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 =AD 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

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.=20

“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

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

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

“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.

SpaceRef staff editor.