The times., 1899-02-27
CARBON vAPoR IN THE SUN.
An Interesting BIT of Astronomical
ehseryatiou.
CFrom the New York Tribuue.)


dainty piece of spectroscopic work
by Prof George L. Hale, Director of the
Yerkes Observatory, has recently come to
light. although it was performed several
months ago. In the solar spectrum there
were long ago recognized bands that in
dicated the presence of carbon. But
whether that substance was in the suns
atmosphere or in the earth's, and, if the
former suppositon were correct, in what
part of the immense gaseous envelope of
the orb of day. no one dared to say with
confidence.
1t has been suggested. to be sure that
the dazzling brillianCe of the sun is due
to minute particles of solid carbon floating
in that luminous shell, the photosphere.
But this theory, while having the air of
probability. has not yet received sub
stantial demonstration. Until Prof. Hale
took up the investigation the nearest ap
proach to evidence that there is carbon
in the sun at all the indefinite an
| nouncement. in reports of the eclipse of
January, 1898, that in some of the photo
graphs taken of spectra of the appendages
of the sun carbon bands had been detect
ed.
What Prof Hale has done is to locate
the carbon with precision, and thus to
establish its existence beyond a doubt.
One element of his success was the size
of his new telescope. While he was still
living in Chicago and conducting now fa-
nous work at his private observatory. he
had a twelveinch refractor, which gave
him an image, at the eyepiece, only two
inches in diameter But with the i'm
meEse forty-inch refractor at Williams.
Bay he is able TO get seven-inch image
Setting the slit of his spectroscope on the
a1pr # hot h.,
observe hundreds of lines. representing
the gaseous layer known as the chromo-
sphere, and lying just above the photo
sphere Among these he found a consid-
cradle number that had never before been
catalogued. But he also noticed that a
certain shaded band, indicating carbon and
situated near the small b. line, was
beautifully revealed. 1t was resolved
into its component lines. spaced from
each other in that wonderfully rhyth-
mical manner that is still puzzle to
the expert physicist. The clearness with
which these lines were defined had never
before been approached.
new and decisive experiment was now
found TO be feasible. BY slight change
in adjustment the slit of the spectroscope
was alternately made to cover the edge of
the phOtosphere-what is TO ordinary peo-
pie the hard substantial disk of the sun
and then the atmospheric layer just above
it-something never seen without instru-
mental aid. This shifting of the instru-
ment was attended with a surous change
in the carbon lines. At one moment they
were bright and at another they were dark
Every spectroscopist knows that when
an incandescent gas is viewed directly it
gives bright-line spectrum, and when an
other source of light is placed behind it.
so as TO allow a different radiance 10 shine
through the layer of vapor. the lines will
be dark. 1t was thus demonstrated that
the carbon existed in the form of vapor in
the chromospheric layer and that when
only this layer was covered by the slit
Of the spectroscope bright lines were visi-
bic. But as soon as the slit was placed
over the photosphere the light of the latter
coming through the chromosphere. would
produce black lines.
After having settled the fact that the
carbon which produces the familiar mark
ings is in the solar atmosphere Prof Hale
undertook to ascertain its exact position
therein. He then found that ii was in the
lowest part of the chromosphere. When
that particular envelope was in an undis-
turbed condition the carbon came first,
iron next and then sodium. magnesium.
helium. calcium, and hydrogen But when
an eruption occurred, tossing the chromo-
sphere up into enormous billows and de-
stroying all sembance OF definite arrange
ment. the position was not well defined.
Prof Hale is satisfied that the car
bon layer is thin one, and that normally
it lies down within 500 miles of the suns
surface-a conclusion that harmoniZes
well with the notion that the glow of the
photOsphere emanates chiefly from parti-
cles of solid carbon suspended therein
For il is highly probable that the intense
heat of the sun-estimated by some scien-
lists al 5000 degrees centigrade would
vaporize little OF the carbon in the lu
minous cloud shell and send it up into
the chrOmosphere.
II was only under the most favorable
conditions of terrestrial atmosphere and
other related factors that Prof. Hale
could make these observations The deli
cacy OF the work is shown by this fact
Measuring sizes and distances with mi
crometer requires the utmost stability OF
apparatus and steadiness of atmosphere.
Yet so firmly mounted is the immense re-
tractor at Williams Bay that Prof
Barnard can perform this task while the
driving clock is being wound. But when
that operation was performed in the mid
die of Prof. Hale's examination of
the spectrum of the chromosphere the car
bon lines disappeared in an instant 1t is
possible thar the great thirty six-inch glass
OF the Lick Observatory, in California
may be able TO show these lines well de-
fined; but with that exception it is not
likely that any other telescope in the
world will admit of an observation such
as the talented young director of the
Yerkes Observatory has been so slow in
reporting.