The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1868-11-19
RECENT SOLAR DISCOVERIES.

IN solar 1nySlGS--pernapS AT bhls moheuS bho
most progressive department In science.
Though much more detailed knowledge pro-
badly remains to be reached by prolonged OBJ
seryation, we may say broadly that the spec
troscope has now revealed the nature Of solar
prominenoes-the red flames of the eclipse
Just as two years ago the same beautiful
method solved the sun.spot problem, and not
long before settled the vexed question Of the
constitution of nebul1. Solar science belongs
essentially to our own time. The ancient faith
that the great luminary was sphere OF ineon-
ceivable Brightness and spotless purity was, 1t
is true, rudely disturbed two centuries and a
half ago, when Galleo and his contemporaries
observed that the solar disc was subject to
eruptiops of dark spots long supposed to be
OPAQUE clouds or solid bodies hiding portion
of the inoandescent surface. But nearly l50
wears elapsed before Wilson's discovery that
the spots were cavities in the phoosphere "a
d. discovery now absolutely confirmed by the
modern observations of Mr.. De la Rue and
Others), and then another century passed
before it was ascertained why these cavities
looked dark and what was the nature OF the
disturbances which produced them. This has
been the work of the last few years. Two
rival theories for short time struggled for
preGminence. One of these, due to NJ. Faye,
explained the phenomenon by supposing
that the mass of the sun was composed of
nebulous matter too much disorga-
nized by its excessive heat to
shine with much brilliancy, while the
light was due to the partial condensation of
the vaporous surface into incandescent particles
in the cooler atmosphere. Aspot, according to
this view, was produced by au up-rush of the
superheated and less brilliant vapor through
the photosphere. The other theory was sup
ported by three English sstronomers-Mr. De
la Rue, Mr Balfour Stewart, and Mr.. Loewy
who had been making diligent solar oeserv-
atiOns at Kew. Their theory was based on the
established fact, that while the bright photo
sphere full of incandescent particles envelops
the sun, the photosphere itself is in its turn
surrounded by an absorbent atmosphere; aud
they held that a spot was produced by q
down-rush of this atmosphere into the region of
the photosphere. Partly by displacing, and
partly by obscuring the photosphere, the
whirlwind of atmosphere, according to this
view, darkens the cavity of the spot. Much
evidence was accumulated in favor of the
English theory, but it was not conclusively
established until the year 1866, when Mr..
Lockyer applied to the investigation the same
method OF spectrum analysis by the aid Of
which Mr.. Higgins had short time before
ascertained tho constitution of nebule.
AS this journal is not exclusively addressed
to scientific readers, We may be excused
short depression to explain the nature Of this
marvellous weapon of modern science. Every
one who has seen a rainbow knows that a
white beam of light opens out, when refracted,
into number of divergirg beams of various
colors, from red to violet. This spectrum,
when produced by the light of any incan-
descent solid or liquid matter, is always con-
tinuous; that is to say, the color changes
gradually from red, through yellow, green,
and blue, to violet; but there are no gaps in
the spectrum wholly devoid of light If, how
ever, an atmosphere of absorbent gases is in
terposed between us and the luminous body,
the spectrum, when carefully observed, is
Il L. r IL
lines corresponding to rays OF particular re-
Tranquility, to which, for some reason or
other, this atmosphere is Opaque. Every
different gas stops different kind of light, so
that, by looking at the spectrum, it is possible
to say, from the position Of the dark lines,
what the atmosphere between us and the
luminous body is composed Of The spectrum
from the sun is crossed by multitude of
these lines, which have already told their
story as to some of the constituents-iron,
hydrogen, sodium, and others-of the solar
atmosphere which partially wells the splendor
Of the photosphere. Thus far we have re-
counted the results of comparatively old ex-
periments, but a new observation of grand
Importance was made by Kirchhof. He
observed the spectra, not only OF solid bodies,
but of burning gases and vapors; and he
found that in the latter case, instead OF getting
continuous spectrum crossed at intervals by
dark lines he saw nothing but system Of
brilliant lines across an entirely obscure
background. And this was not all. 1t was
known that the vapor of sodium had the power
OF obscuring particular portion of the yellow
light of the spectrum, forming, in fact, across
the yellow belt, two very marked lines, which
are familiar in the solar spectrum, and are
known as the d lines. When sodium was set
on fire, it was found that the whole spectrum
of the vapor was composed of two bright
yellow lines, exactly corresponding to the two
dark lines produced by the same vapor when
interpesed as an absorbing medium. This
observation was soon generalzed into the re-
eognised law that the spectrum produced by
any blazing gas or vapor is never continuous,
but always consists in series of bright lines
separated by obscure intervals, those lines
corresponding precisely to the dark lines
produced by the same gas or vapor
In non-luminous state. The in
stant, therefore, that a spectrum ia observed,
we know what the nature of the burning
matter is. II the spectrum is absolutely con-
tinuous, it is simply solid or fluid matter, in
cluding, be it observed, the case of minute
solid or fluid incandescent particles floating in
q gaseous atmosphere, which must be, in fact,
tbs constitution of the solar atmosphere. II
this spectrum is crossed by dark lines, We
further know that between ii and us there is
an absorbing atmosphere; and lastly, if the
spectrum consists only of isolated bright lines
we are sure that We are looking at blazing gas
or vapor, and in very many cases it is possible
to identify the particular gas or vapor by
which the lines are produced.
With these facts in his mind, the least
scientific reader will easily understand the
application of the method to the investigation
OF un.spots. If the spot was composed o
superheated gas from the body of the sun