Delaware state journal. [volume] (Wilmington, Del.) 1870-1883, 1872-03-05
THE sun.
Important Discovery During the Late
Eclipse.

Important Discovery During the Late
Eclipse.
Professor Respighi, the eminent Italian
spectroscopist, succeeded 10 making a note
worthy advance in our knowledge OF solar
physics during the progress Of the eclipse of
last December; and, what is OF even greater
importance, he employed a totally novel
method OF observing the eclipsed sun, his
actual discovery being probably but the first
fruits of this method. We propose to give |
Professor Respighi, and description Of
those features Of the method which consti- |
tute its importance. But for obvious reasons |
this is not the place for description of the |
instrument employed by Respighi.
1t will be in the Remembrance of many |
OF our readers that DUNG the eclipse OF De- |
cember, 1870, considerable attention was /
directed 10 the circumstance that the SUMS |
corona appeared 10 consist OF two distinct |
portions. Close 10 the black disc of the |
moon there was seen bright ring of pearly |
light, not uniformly wide, but nowhere |
extending TO distance much exceeding a |
fourth or fifth part (for accounts differed) OF |
the moons apparent diameter. Outside this |
nng-formed corona appeared much more |
extensive but much fainter halo, radated In |
lis general structure, or rather clOven in |
Nelluin pluiGH ny Ctllhin Mtll QuTk
Iiils or gaps, There was so sudden a de- |
graduation OF luminosity near the borders of |
the bright inner corona Bs to suggest very |
strongly the idea that the two cOronas are |
totally distinct solar envelopes. Indeed, It |
was proposed 10 give the inner corona
name specially invented for the OCCASION
the name Leucosph6re-which fortunately |
was not received with favor. Indeed, it |
presently appeared that the supposed dis |
w n n at oil ha ~
nature OF the corona having been recognized |
lGo years ago, and having since been
repeatedly confirmed during total eclpses. !
So far back as 1852 our own astronomer
royal had suggested for the two envelopes
the names of the "Ring- formed" and the
''Radiated" coronas. 1t must bo added,
furthermore, that when favorably seen, the
g. g. fiSg formed eczoaa is not peary
white in hue, but marked by distinct tingle
OF rose color.
Now, astronomers have been endeavoring
since the great eclipse OF 1860 TO determine
the real nature Of the light emitted by the
various parts Of the corona. They have
sought, in fact, 10 apply the modern method
Of observation called spectrum analysis 10
the corona, as they had already applied 1t 10
the prominences; and thus 10 learn whether
the light oil the corona comes from glowing
vap0r or from lncandescent particles, or is
merely sunlight reflected from opaque matter
spread in a sort of cosmical dust around the
solar orb.
But important difficulties stood in their
way. They did obtain on turning their
spectroscopes towards the corona spectrum
which, in itself, indicated that the source Of
light was glowing vapor. A certain green
line appeared, which, il it really were the
spectrum OF the corona, could hear no other
Interpretation. But it was not clear that this
green line spectrum belonged to the corona
at all-the doubt arising from the lact that
tho green line still made lis appearance
when the spectroscope was turned 10 parts
of the sky 10 which The corona could not be
supposed to extend. This is easily explained.
In these days every one knows that the
suns light, when dealt with by specro-
scope, presents rainbow tinted streak
crossed by dark lines, and that these dark
lines indicate the presence, in the sun, of
The vapors OF many familiar elements-as
iron, copper, zinc, and so forth. But ii we
turn speclroscope toward the sky, or even
towards sheet Of white paper illuminated
by the sun, we see the same dark lines; yet
we know that there is no glowing iron vapoT
in the sky o. in the paper. The fact really
is that we receive from the sky, and from
the paper, reflected sunlight, and so naturally
find in such light the qualities of sunlight.
How, il in like manner, when the observers
of recent eclipses have seen a bright line
spectrum, while examining the corona, they
have been in reality examining only reflected
light, and 80 had still 10 determine the true
source OF the light9 Nay, rather, il was
clear that from some parts of the sky they
did get this green line from reflected .ighl; I;
how, then, were they TO distinguish where
the inherent luminosity ceased and the re-
f1ected luminosity beganp
The problem seemed intractable; but, as a
matter of fact, Professor Young, OF America,
solved 1t very satisfactory by carefully con-
aiderlng the amount oil this green luminosity
received under different circumstances. We
need not examine his reasoning, but the
result may be very simply stated. He
inferred that IN all probability q region
somewhat more extensive than the ring
formed corona shines with this green line
forming light. We believe that no one who
examines and understands Professor Young's
reasoning can doubt that lie legitmately
established this conclusion. 1t follows that
ths ring formed corona, or somewhat
larger region around the sun, is true atmos-
phenc envelope, The interest Of this dis
covery is enhanced by the circumstance
that the green line of The coronal spectrum
is conspicuous feature of the spectrum OF
our own auroras. Professor Respighi has
confirmed Young's discovery. In confirming
il, however, he has added another equally
important,
IhuS tar We nave Deen speaking o.
green line OF The inner corona. But il
occurred 10 Respighi that he would en-
deavOr 10 see a green image of this solar
envelope. There were two ways in which
he might try to effect this. The first is q
method devised independently by Huggins
and Zollntr, and first successfully applied by
the former, though occasionally called the
Jansen Lockyer method (being coniounded
apparently with perfectly distinct method
OF observatory. The other was proposed
by Fraunhofer, 10 the very infancy of th'
science OF spectroscopic anylysis-and hal
lately been revived by the Italian astrono
mers, Secci and Respighi. Neither method
need be described, but each has this effect
that when the source of light is glowing
gas, theu, instead of a spectrum of such and
sucn lines, there is formed series of CORES
pondingly coloTed images Of the source o
light Thus when one of the solar promin.
ences is observed in this way, instead of
red, an orange, green, and an indigo lin'
(and other faint lines), The methods referred
10 show Ted image OF the prominence, al
orange image, green image, and an lndig
image (ths images corresponding to tn
lainler lines being too faint TO be discernibl
under ordinary cireumstances.)