Evening star. [volume], June 29, 1932, Page A-11, Image 11

About Evening star. [volume] (Washington, D.C.) 1854-1972

Image provided by: Library of Congress, Washington, DC

                
'SCIENCE MEASURES
METEORITES' AGE
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Development of Sensitive
' - Method Reported by
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German Physicist.
BY THOMAS R. HENRY.
The age of meteorites now cân be
measur%d.
Development of an extraordinarily
sensitive method for this hitherto im
possible measurement has just been re
ported by Prof. F Pancth, German
physicist, to the Committee on the
Measurement of Geological Time of the
National Research Council.
Applying his method to samples of
these celestial visitors, collected all over
the wond, including several from the
United States, Prof. Paneth finds that
the oldest cannot boast of more than
3,000,000,000 years, which is well within
the time since the formation of the
solar system. This leads to the conjec
ture that they are parts of the solar
system. -,
The method reported by Prof. Paneth
has far-reaching applications to other
time-measurement problems upon which
the American committee is at work,
especially the determination of the age
of deposits of copper, silver and other
metals which are very faintly radio
active! It consists in determination of
the amount of rare gas helium, product
of atotnic disintegration, in a given
amount ot the metal.
Supplants Lead Method.
Hitherto the most reliable method of
measuring geological time has been by
the lead-ratio method. The two radio
active elements, uranium and thorium,
disintegrate at a fixed rate into a final
state which is a form of lead differing
in atomic weight from ordinary lead.
The amount of lead in proportion to
these parent elements in a sample of a
deposit is a measure of its age. Helium
Is one of the by-products of the disin
tegration. It is, however, a light gas
■which will not enter into chemical com
bination with anything in nature, and
which, consequently, escapes easily and
becomes diffused in the atmosphere.
Lead, the heavy metal, "stays put." In
the past measurements of the helium
content has given much lower figures
iof the age of a deposit than the lead
method.
The advantage of the helium meas
urement is that this element can be
determined in much smaller quantities.
The geologist using ihe lead-ratio
method can consider only the special
kind of lead which results from atomic
disintegration, and in small samples it
is impossible to distinguish this accu
rately from ordinary lead, which has
not time significance.
"Hitherto," says Prof. Paneth. "the
lead method has been almost exclu
sively recognized as reliable. There
are. however, materials which hold the
helium completely fast—the metals.
Even by heating an iron meteorite to
1,000 degrees tor many hours only a
negligibly small fraction of the helium
is dissipated, obviously only that close
to the surface. We can therefore as
su ma with certainty that the amount
of hélium which has been formed since
the èotnsôlidation of the meteorite still
is completely inclos:?. Only the helium
irom.tfce ring may have escaped.
Acoqr»cy Increased.
"Hate the helium is just as reliable
as tha lend method, over which it has
some advantages, and we are In a posi
tion tt> test for helium in small quan
tities. ' Iron meteorites contain helium
only A the order of a hundred-thou
sandth· to a millionth of a cubi; centl
met;r g··. By a spécial method
of dissolving the meteorite away from
air we can measure a millionth of a
cubic centimeter of helium with a max
imum error of 1 per cent. By using
several grams of a meteorite it is always
possible |p increase the accuracy of the
helium measurements in proportion.
"The 100,000,000th to the 10,000,000,
000th part to a gram of lead, formed
according' to the laws of radio-activity
by the same decomposition, cannot be
recognized, in the presence of a much
larger amount of normal lead present
in the meteorites, for one contains on
the averagft an amount to which the
lead isotopfc formed by the decomposi
tion of uranium and theorium would
not be even one part per thousand.
"It appears that to determine the age
οt iron meteorites the helium method
Is the only way yet applicable, and the
customary objection of the possible es
cape of helium does not apply. What
applies to iron meteorites also applies
to native metals. It is probable that
the error from the escape of helium
becomes important only in the radio
active minerals which contain much
helium, to which investigation hitherto
has been confined.
"For the iron meteorites we have
estimates of age for which there is still
an uncertainty, because they give us
maximum values, but the particular In
terest is in the maximum age, because
before all it must be decided whether
the age of the meteorite is not too
great to consider It as belonging-to our
planetary system. The highest age yet
ascertained seems to be not above
8.000,000.000, which is within the time
since the formation of the solar
aystem."
RESTRICTION PLACED
or' CIRCUSES IN D. C.
Consent of More Residents of Areas
Adjoining: the Sites Is
Now Necessary.
Before circuses and carnivals can be
Staged hereafter in the District, the
consent of more residents of the areas
adjoining the sites will have to be
obtained, under an amendment to the
police regulations wiopted yesterday by
the District Commissioners.
Acting in response to protests filed
by residents located near the grounds
of a recent carnival, the Commissioners
increased the area from which consent
must be obtained by promoters of the
attractions and also specified that
consent be obtained from property
owners as well a;; occupants of the
properties.
Under the amer.ded regulation the
written consent of three-fourths of the
occupants and owners of the premises
■within 500 feet of the site of the
attraction must be obtained. The rule
previously applied to residents living
within 300 feet.
PERMIT IS AUTHORIZED
FOR PANTHEON SIGN
fl5. C. Commissioners Approve Ap
plication *n Behalf of
War Painting.
An application by the Pantheon
Corporation for a permit for erection
of a sign on its exhibition building, at
New Jersey avenue and C streets, adver
tising its showing of the huge World
War painting, Pantheon de la Guerre,
was approved yesterday by the District
Commissioners, after the size of the
proposed sign had been reduced dras
tically.
The application called for permission
to erect a sign, approximately 1,1S2
square feet in area, which had the
approval of the Pine Arts Commission.
The Commissionners, however, acting
on a recommendation by Capt. Hugh P.
Oram, director of inspection, specified
that the area of the sign be not more
than 200 square feet.
A hypothetical ouestion which took
87 minutes to propound was asked a
witness in a valuation proceeding· la
ft (uperior court in San Francisco.
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