Archaeology Magazine - June 1960 - 60

active decay of uranium, thorium and
certain isotopes of potassium, present
in all earth materials, is accompanied
by emissionof alpha, beta and gamma
rays. These rays, striking through the
earth materials that contain them, will
displace electrons from their stable
sites into unstable orbits or traps, and
thermoluminescentenergy is stored in
the particular materials involved. This
energy is proportional to the total radiation dose absorbed by the material.
In practice, the thermoluminescent
glow curve of an object is determined
in the following fashion: A portion of
the object to be dated is powdered, and
the powder is carefully spread on a
hot-plate. The hot-plate in turn is enclosed in a light-tight box with such
geometrythat the light given off by the
sample is observed by a photomultiplier tube. The sample is then rapidly
heated. The output of the photomultiplier tube and the surface temperature of the sample are recorded and
plotted against each other. The resultant curve, showing light emitted
as a function of the sample temperature, is called a thermoluminescent
glow curve. Next, the radioactivity of
the object is determined in alpha and
beta counters. For any material the
amount of thermoluminescentlight, divided by the mean radioactivity, is
proportional to the number of years
that have elapsed since the object was
last heated. Certain other corrections
are necessarybefore this may be translated into an absolute date. Various
materials range in sensitivityto radiation. The sensitivityto radiation is determined by annealing the sample at
high temperatures and subjecting it to
an artificial dose of x-ray radiation.
The new glow curve, determined from
a standard, artificial dose of radiation,
is a measure of the sensitivity of the
materials to radiation damage.

This method of dating is applicable
only to materials which have undergone no chemical alteration or recrystallization. Lava flows which have suffered recrystallization,or pottery which
has been placed in limey ground,
where salts, limestone, etc. have deposited on the pot, cannot be dated
by this method, as thermoluminescent
glow is associated with recrystallized
materials regardless of their age.
Many problems remain to be solved
before dating by thermoluminescence
can become an established procedure.
Unfortunately, other kinds of damage,
apart from radiation, will displace
electrons into traps and cause thermoluminescent light. A small amount of
glow is generated in a sample by the
mechanical damage of grinding in
sample preparation. A certain amount
of glass is formed in ceramic ware as
it is initially fired in a kiln. If this
glass later devitrifies,spurious signals
are obtained. Results to date suggest
that fewer problems are associated
with the dating of recent lava flows by
use of thermoluminescencethan are associated with the dating of ceramic
ware.
Solomon's Temple
Continuing demand for copies of "A
Reconstructionof Solomon's Temple,"
which appeared in Archaeology 5
(1952), has led to the reprinting of
this interesting article. It is eight pages
in length and lavishly illustrated with
pictures of the Temple model constructed by Mr. E. G. Howland in accordance with the results of Prof. Garber's research.
Copies may be obtained at 35 cents
each from the Archaeological Institute of America, 5 Washington
Square North, New York 3, New
York.

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Journal Resumes Publication
The Plains Anthropologist,quarterly
journal of the Plains Conference,will
resume publication with issue No. 9,
scheduled for release in May, I960.
The Plains Conference is an informal
organizationof archaeologists,ethnologists, linguists,physical anthropologists
and other scientists whose research interests center in the Plains area of the
United States, Canada and the bordering tiers of states and provinces. The
Conferencehas met annuallysince1951.
The journal was inaugurated in
1954 as the successor to the Plains
ConferenceNewsletter, begun in 1947.
Now reorganized, each issue will run
to approximatelyfifty pages.
Subscriptionrates will remain $2.00
during I960. Correspondence should
be addressedto James B. Shaeffer,Editor, Plains Anthropologist, Research
Institute, North Campus, University
of Oklahoma, Norman, Oklahoma.

Buddha in Cleveland
A recent acquisition by the Cleveland Museum.of Art is this charming
bronze Buddha, 8V4 inches high, of
Siamese origin. It dates from the seventh century (Mon-Dvaravati period).
The statuette is part of the Norman
O. Stone and Ella Stone MemorialCollection (58.334).

Archaeology Magazine - June 1960

Table of Contents for the Digital Edition of Archaeology Magazine - June 1960