Evening star., 1927-05-29
TREE RINGS HELD
CLUES TO WEATHER
Scientist Sees Their Value in
Forecasts, Judged from
Observations.

Announcement by DIR. A. E. Doug
lass of the University of Arizona that
the study of the sequence of tree rings
Is likely to be of value in longtime
weather forecasting recalls that tree
rings already have furnished valuable
clues to dating columbian history
of America.
This method was used in conjunc-
ton with pottery types in fixing the
time when Pueblo Bonito. New Mex
leo, fiourished as the metropolis of
America in the years before 1892.
DIR. Neil NJ. Judd. leader of the Ma
tional Geographic Society expeditions
to Pueblo Bonito, with whom DIR.
Douglass collaborated in applying his
method to the Pueblo Bonito ruins.
writes:
."The oldest living things in Amer.
lea are it's big trees, the sequoias OF
the Sierra Nevada. The pines and
jumpers of Arizona and New Mexico
are much younger than the sequoias;
but, like the latter, tney are older than
any other living thing in their own
neighborhood. Some of these upland
trees are between 400 and 500 years
Oh age. ana IL IL IIOI at dll
that still older ones may be found.
Tree Life History Revealed.
1.-The life history of almost every
tree is revealed by its own cross-sec-
tions, each years growth being re-
corded by new ring. If any given
year has been one of scanty rainfall
the particular ring for that year will
be relatively thin, and, conversely, If
the rainfall has been abundant, there
will be corresponding increase in the
thickness of the annual ring.
Periods of drought or excessive
moisture, it has been learned, tend to
repeat themselves at fairly regular in
tervals. resulting thus in a more or
less orderly sequence Of thick and thin
annual rings. which do not vary, to
any marked degree, in all the trees OF
any one district.
Certain of these ring series possess
individual features that quickly iden'
tify them, no matter in what locality
they may be found. and these are nat
urally utilized by the Investigator as
keys to the problem he is seeking to
solve. And what is true of living trees
is likewise true of dead trees, and
beams or roofing timbers from prehis
toric ruins. like Pueblo Bonito.
From the foregoing it will be OBJ
vious that il any overlapping series
of annual rings can be discovered
that is, If a given sequence of rings
can be found both in beam from
Pueblo Bonito and in a tree still liv.
ing-it will be possible to date the for.
mer with reasonable exactness.
Tree Calendars Missing Link"
"Such a direct connection, however.
with no intervening links in our time
chain from the beams of prehistoric
Pueblo Bonito to the living trees of
northern New Mexico. is rather be-
yond the range of possibilities; the ex'
plorer's task is rarely quite so easy as
that.
1T seems necessary. therefore. in
the present case. to find a connecting
link in this time chain. and that was
the especial object of q subsidiary ex'
pedtion authorized by the research
committee of the National Geographic
Society in connection with the explora'
ton of Pueblo Bonito.
''Cross-sections from 40 timbers un'
earthed during the explorations of two
seasons were examined by DIR. Dough
lass with very instructive results.
These beams, taken from the eastern
portion of Pueblo Bonito. all seem to
have been cut within period of IL
years.
Some timbers exposed in the north
western quarter of the ruin, however,
were cut several years earlier, thus
corroborating the archaeological evi
dence previously presented"