Bristol news. [volume] (Bristol, Va. & Tenn.) 1867-189?, 1873-04-22
THE SPECTROSCOPE IN AS
TRONOMY.
Lecture by Professor Young.

Last evening Professor c. W. Your g
of Dartmouth College, lectured at
Cooper Ins ,itute on the astronomical
uses of the spectroscore The hall
was very we'll filled. Professor Young
spoke as follows He felt some degree
of trepidation at speaking before a
metropolitan audience which had so
lately listened to Professor Tyndal,
that great scientific master. yet he
was somewhat reassured when he
thought that, having heard such
man. they must have come to love
science for its own sake. The spec
troscope is the most powerful instru-
ment in modern science, which in
ten years has by its aid discovered
things which without it would perhaps
hive been forever unknown. This
instrument allows the scientist to
detect the minutest trace of an eIe-
ment, the only condition being that
it shall be vaporized and made lu-
minous each metal gives its own
characteristic spectrum, which an
expert is in no danger of confounding
with any other; sodium gives single
or double line of yellow light; siren
tium gives eight bright lines; silver
is otherwise characterized, and when
the spectra are thrown upon the
scene you readily see that there is
no mistaking one for another, When
brass is vaborized it gives the lines
of copper and zinc. being composed of
those metals. As the lecture is to
show what SpectrOscopy has Taught
us in regard to the nature of heavenly
bodies, it must be noticed that the
elements will give Their spectra no
matter how far away they are, pro-
vided thier light reaches the earth.
The Spectroscope used in astronomi-
cal observations differs in form from
that used for terrestrial purposes, but
it is the same in principle; its pnr-
pose being to enable the observer to
detect the lines in the spectra and so
to determine the nature and cOndi-
ton of the subject undergoing ex.
animation. When turned upon tie
sun the instrument gives the solar
spectrum of which, in photograph,
Kirchof's map is here given showing
the lines which were first noticed by
Wollaston, afterwards described by
Fraunhofer, whose name they bear
being called FraunhOfer's lines-but
made of real scientific value by
Kirchof when he discovered that
the bright line of sodium correspon-
ded in position to a certain black
line in the spectrum, and that when
the light was passed through the
vapor of sodium the bright line be.
came dark. Spectrum analysis shows
that all of the substances present in
the earth are in the sun, but the re-
verse is not necessarily true, as in
the spectrum of the chromOsphere
there are some lines the meaning of
which has not yet been explained.
Many metals have been shown to
exist in the chromOsphere, and some
substances which ore not metals or
gases. such as sulphur. These sub
stances give dark lines in the solar
spectrum, but colored lines when
burned oil earth their lines are re-
versed sulphur and cerium cannot
always be detected in the chromos-
phere, probably because the lines are
so bright that the light behind cannot
reverse them: it is possible to tell
what metals are there, though it is
impossible to say what are not.
klrchofH theory of the snn was that
surrounding the main body was mass
of incandescent vapOr, but spectroS-
cOpic examinations made during the
eclipses of 1868 and the following
year gave no evidence of the exis-
tence of such vapor, and from other
observations, especially those of1S71.
it was rendered not doubtful that the
dark lines are formed by metals ex-
isting in great body of finely divided
matter about the sun. Higgins turned
the spectroscope upon the stars, and.
observing AIdebaran, found titanium,
iron, sodium, and hydrogen lines,
indicting the presence of those metals |
and altogether, by Father Secchi and |
others, twelve stars have been invests
gated and found to pc composed like
the sun. Vogel found iu Uranus two |
broad, dark bands, the meaning of |
which is not yet known, and the |
planets shining by reflected light give
the same lines as the sun. But thew
give strong dark bands also. When
the sun is near the horizon Its ligbt
comes TO us through thick strata of air
holding vapor, and then the bands
nay be detected in its spectrum. Ifl
the bands mean vaporladen atmos.
phere it is not impossible that Venus
and Mars, whose spectra show them
strongly. may be inhabited. This,
however, is mere conjecture and
valueleSs as science. The spectros
cope has been used 10 examine the
and has determined in regard
10 some of them what astronomy,
when the telescope alone was used,
eft undetermined. 1t was long a
question whether nebule we're groups
)fstars, Irresolvable, or mere tenuous
natter. but when the spectroscope
vas turned upon them they were
'ound to be incandescent gas, for their
pectra gave bright bands, as also did
hose Of the comets, although in the
after case the proof was not certain,
ince they might be composed of
matter-quinine, for in
tance. What was proved however.