Evening star., 1926-12-14
WASHINGTON LEADS
IN SUN HEAT TESTS.
Delicate Instruments From
Smithsonian Shipped to :
Other Continents.

Seven silver disk pyrheliometers are
shortly to go out from the Smith
s0nian Institution to India. Switzer-
land, Germany and various observa'
tories in the United States. The world
has accepted these instruments as
standard for measuring the suns heat
received at the face of the earth.
They were invented and perfected by
DIR. G. G.. Abbot, assistant secretary
of the Institution, in the course of his
researches on solar radiation, and they
are made only at the Institution.
Some so of them have found their
way since 1913 to Government and
private observatories here and abroad.
The basis of the apparatus is 4
hlackened silver disk as big as a half
dollar and three times as thick, con
tanned in q tube with small aper
ture to permit the entrance of sun
beam. The disk absorbs the rays and
IS warmed. A cylindrical bulb ther-
mometer is inserted in the silver disk
20 record the effect of the rays. Each
thermometer has to be corrected to
insure an accurate reading.
Only Standard Instrument.
To check the accuracy Of the silver
disk instruments. DIR. Abbot also in
vented q watertiow pyrheliometer, a
more complicated and delicate instru-
inent whose precision is known to
some ten-thousandths of degree. OF
this instrument the head of the Ger
man meteorological service said in
1918: There is but one standard
pyrheliometer in the world and that
is at the Smithsonian Institutions
Astrophysical Observatory"
The universal acceptance of these
i. Sw1ls ,%<r. &InsN
leading position which the Smith
sonian occupies in the study of solar
radiation Besides the pyreliom-
eters. the institution has perfected
for the world the bolometer. which
measures the heat of the separated
rays of the spectrum, recording tenn
perature changes as low as one
millionth of q degree. Secretary
Langley invented the bolometer, but
DIR. Abbot has greatly improved on
this invention.
The pyranometers are due to DR..
Abbot and Mr.. Aldrich jointly. One
Is for measuring the intensity OF the
sky's brightness, while the other
measures the radiation of the earth to
space. This second instrument, called
the honeycomb pyranometer, is the
only apparatus in the world which
has measured the radiating capacity
of the human body. In collaboration
with DIR. Benedick of the Carnegia In
Stitution's nutrition laboratory, DIR.
Abbot experimental some years ago
to find that the human body was an
almost perfect radiator.
One of these honeycomb pyranom-
eters was taken to the Arctic Circle
In the Maude when Amundsen's col
league, Sverdrup, was trying to drift
across the North Pole, and many
measurements were taken Of the earth
rays going out through Arctic night.
One of the rareSt achievements to
the credit Of the Smithsonian astro-
physicists was the measurement Of
the suns heat at a point Is miles
above the surface of the earth. To
accomplish this, DIR. Abbot prepared
a modified form of the silver-disk
pyrheliometer to be attached to a pair
of sounding balloons made of expan-
Sible dental rubber. In cooperation
with the Weather Bureau balloon ex-
perts, this was released by Mr..
Aldrich of the Smithsonian from
Omaha in 1914. 1t ascended Is miles,
automatically recorded the intensity
of solar radiation where 24-25th of
the atmosphere lay beneath it, col
lapsed one of it's balloons and was
waited gently to earth. 1t was picked
up safely in Iowa, $50 miles distant
from its starting point. The measure
ments agreed almost exactly with the
results computed from those made at
the earth's surface by the Smith
sonian, and SO gave strong proof of
the correctness of the theory en-
ployed by Smithsonian scientists in
their study of the variability of the
sun which may lay a new basis for
weather forecasting.