Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-12-03


other sciences
Two series of National Geographic
Society expeditions took part in arriv-
ing at the final result. One series,
comprising eight expeditions led by
Neil M. Judd, explored year after year
the Pueblo Bonita ruins in New Mexico
and patiently dug from tons of earth
hundreds of art objects household
utensils and ceremonial paraphernalia.
The other SERIES led by DR.. E. A. Doug
lass. studied tree rings from Pueblo
Bonita ana dozens of other ruins.
Value Of Findings.
DR.. Gilbert Grosvenor, president of
the National Geographic Society. in
assessing the value of the finds of the
expedition, says:
They have pushed back the historic
horizons of the Southwestern United
States to a period nearly eight CEN
turtles before Columbus crossed the
Atlantic.
They have discovered not only the
age of the great communal dwelling of
Pueblo Bonita, metropolis of our aborig-
inal Southwest, but also have dated
some 40 other ruins whose time of oc-
cupancy hitherto had been unknown.
Moreover, they have developed a
tree-ring calendar which can be APP
piled to all early ruins in which datable
timbers exist.
"A collateral finding of great inter-
est. yet to be developed, is the possible
relation between the weather cycles
clearly revealed in this tree-ring calen-
dar of the Southwestern United States
and similar cyclic variations being re-
corded by third National Geographic
in until !,
the Smithsonian Institution), an expe-
dition which still is in the field. at
Mount BrukkaroS, Southwest Africa,
making daily observations Of solar ra-
diation."
Dates Of Ruins.
In many instances, DR.. Douglass re-
port points out, one group name is APP
piled to several ruins. The 'talkative
tree rings" enabled the explorers to date
each ruin of the groups studied. Thus,
in the Mesa Verde group, Cliff Palace
is dated 1913; Oak Tree House, 11l2;
Spring House. 1ll5; Balcony House,
1190-l206; Square Tower House, 1904,
and Spruce Tree House. 1915 and 1852.
Explaining the procedure by which
the tree-ring calendar was worked out,
Dr. Douglass says:
1.-THE method which we have used in
extending the historical calendar of the
Southwest is the outcome of long at
tempt to read the diaries Of trees. Every
year the trees in our forests show the
swing of times pendulum and put down
a mark. They are monographs, re-
cording clocks, by which the succeeding
seasons are set down through definite
imprints. Every year each pine adds
a layer of new wood over its entire
fNrit rtN-fo Nf krtaV or1A AHn
If every year were exactly the same,
growth rings would tell the age of the
tree and little more. Only in rare
cases would they record exceptional
events of any Interest to us. But a tree
is not a mechanical robot. 1t is a liv-
ing thing, and its food supply and adj
venture through life all enter into It's
diary. A fash of lightning, forest
fire, insect pests or falling neighbor
may make strong impressions on its life
and go into its diary.
But in the arid regions of our South
west, where trees are few and other
vegetation scarce. the most important
thing to man ard trees is rainfall. This
fact has helped vastly in our dating
work, for certain sequences of years be-
come easily recognized from tree to
tree, county to county, even from State
to State:''
Sun Spots Studied.
From sun spots to tree rings seems
a long scientific jump, but it illustrates
how one fact Of science may have far
flung results in other fields, for DR.
Douglass is an astronomer.
Originally my work was study of
sun Spots" he writes. 1T Is known that
there is a periodicity in their occur
rences; they are most numerous at in
tervalS of IL years. AS an aid in that
astronomical investigation, studied
trees, for solar changes affect our
weather, and weather in turn affects
the trees in Arizonas dry climate, as
elsewhere.
THE first confirmation Of our gen.
eraI Interpretation of a relationship be-
tween tree rings and Sun-Spot periods
came in q most dramatic way.
Evidence of the 11-year Sun-spot
cycle had been easily found in Arizona
pine trees. The regularly recurring
periods had been recorded for 500 years
by tree rings, except for the interval
from 1850 to 1925. During that rs years
the tree rings gave no evidence OF per-
iodical changes in the weather such as
were to be expected.
Several years after we had encoun-
tered this puzzling fact the late DR.. E.
Walter Maunder, an eminent English
astronomer, unaware of my findings,
wrote to me that he had discovered that
there were no sun spots between 1645
and IT'S, and that If my tree rings did