The San Francisco call., 1909-06-09
CAREFUL STUDY
OF SUMS RAYS
Elaborate Preparations For
Accurate Measurement
Of Radiation by
Orb of Day
. c. ABBOT. director OF the smith
sonian astrophysical observatory

III Sonian astrophyS1cai ooSerNatOi+s
W. has left washington for Mount
Wilson in southern California. to con-
tinue there during the summer and fali
observations in progress for a number
of years as to the intensity of the
suns rays and the effect OF any varia-
ton in them upon the earth
The Importance of such observations
and the far reaching results that may
be obtained from their success have
been recognized by the Smithsonian In
stitution, so that there has recently
been erected on Mount Wilson small
permanent observatory especially de-
signed for this purpose. Here Mr..
Abbot, with the assistance of Dr. L r.
Ingerson of the University of Wis
consin. will study during the next few
months
| The expedition will also spend some
| time on the summit of Mount Whit
ney. 1880 fet high. where the insti-
tuition plans to erect in July a shelter
OF stone and steel for the use OF sci
entific investigators engaged in re-
searches of any kind for which high
attitudes, dry air and clear skies are
desirable.
In speaking of his work Abbot says:
| Although everybody knows that we
all depend for life on the rays OF the
sun. it is only since 1890 that the
amount of the suns radiation has been
even approximately known. Accurate
measurements are exceedingly difficult
to secure for several reasons. one being
the varied absorption Of rays by the
atmosphere before they get down to Us
on the earths surface.
1T is to diminish these variable and
troublesome atmospheric effects that
the Smithsonian astrophysica1 observa-
tory has sent expeditions TO Mount wiI-
son in California for several years and
is continuing the work there this sum-
mer. The sky above Mount Wilson is
nearly cloudless from May to Novem-
Der, the amount of moisture being far
less than in corresponding months at
sea level. and owing to Mount Wilson's
altitude of over a mile above sea level
the amount OF air which the suns
rays traverse is nearly fourth less
there than at Washington.
The work of former seasons has
indicated that the suns radiation is
not uniform but irregularly variable in
periods of a few weeks or months
and there is apparently some depend
ence of the earth's temperature on
these solar changes A principal OBJ
( iar Of
the observation of any variations of
the sun which may occur, in order to
establish further the relations between
the earth's temperature and the sun.
1t is hoped to continue the work at
least for sun spot cycle OF IL years
in order to study long period solar
changes as well as the shorter ones
just mentioned
With this long series of observa-
tions in view the Smithsonian .astro-
physical observatory has recently
erected on Mount Wilson a permanent
branch observatory well built of ce-
ment blocks and adapted specially for
/ the work. and has stocked it with the
special apparatus required The site
overlooks canyons 1000 feet deep on
three sides and is very favorable for
measuring the rejecting power of
clouds which often I'll these canyons.
During this present season special at
tention will be paid to measuring the
'ultra violet sun rays. Large prisms of
North Carolina quartz and mirrors of
the alloy magnalium have been pro-
cured for this work. because glass is
not transparent to the rays and silvered
glass mirrors do not reflect them. The
air itself ceases to transmit them. and
so in order TO carry the work to the
4 highest measure of success we shall
probably spend some time in August on
the summit of Mount Whitney (145oa
feetl, the mountain celebrated among
men of science as the scene of Mr..
Langley's expedition of 1881.
In order to enable investigators to
carry on observations of anv kind for
which high attitudes. dry air and clear
skies are desirable the Smithsonian In
stitution viii erect. from the Hods-
kins fund. in July of this year on ,ba
very summit of Mount whitney a three
room shelter of stone and steel sub-
stantiaI enough to stand there FOR ce,-
turies- 1t is expected that the wort
there will be a decided aid to tbe -
vancement of the knowledge OF a.
mospherfc air, for which the Hodgktns
fund was bequeathed"
II n