The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1870-06-03
TIE SUNS CORONA.
From the London Spectator.

From the London Spectator.
One problem after another presented by
the study of the sun has been mastered by
astronomers and physicists. They have ascer-
tanned what are the substances of which his
globe is constituted, they have learnt some-
thing of the condition in which those sub
stances exist; they have detected the secret of
the rose-colored prominences which spring
suddenly into view when his orb is eclipsed,
Later came the simultaneous discovery by
Jannsen and our ingenious countryman Lock
yer, that the spectrum of the prominences can
be studied when the sun is not eclipsed, q
discovery fruitful in promise, if it has not yet
brought with it all the results which had been
looked for. More important still was the in
vention by Mr.. Higgins, fdcjJe pTjncepS
amongst astronomical spectroscopists, of a
method by which the prominences can be
seen (''not merely rendered sensible, as Sir
John Herschel justly says by means of the
spectrOscope. Thus it has become possible
to inspect the figure, and what is yet more
striking, the changes of figure, of these
amazing objects. Astronomers have availed
themselves at once of this ingenious method,
and SO far as the prominences are concerned
little seems left to be discovered.
But one imposing phenomenon presented
during total solar eclipses remains yet to be
interpreted. The crown of glory which sud
denly bursts into view when the suns orb is
totally concealed, has proved source of per-
plexity to astronomers and physicists until now,
and may, perchance, yet foil their attempts at
explanation for many years to come. 1t has
been regarded as lunar appendage by some,
as a solar appendage by others, while others
again have supposed it to be merely an opti-
cal phenomenon. In August, 1869, during
the eclipse which offered such important in
formation respecting the colored promi-
nences, the corona was left uniDterpreted In
August, 1869, though several observers scru-
tinized it attentively with the powerful instru-
ments now available to the astronomer, it
still foiled their efforts. The question which
is perhaps of all others most in the thoughts
of the astronomer, is whether the observa-
tions to be made during the eclipse of De-
cember next will suffice to master this stub
born problem.
If we consider the matter Alright, we shall
see that the solution of the difficulty can
hardly fail to afford most interesting infor-
nation respecting the physical habitudes of
the sun, nay, even respecting relations affect
ing the whole economy of the solar sys-
tenn. Regarded as q solar appendage, the
corona is, in some respects, the most amaZ-
ing object within the limits of the planetary
scheme. 1t has been seen (under favorable
eonditions) to extend several degrees from
the eclipsed sun; and degree, in the case of
an object situated at the suns distance,
corresponds to a length of seventeen hundred
thousands of miles. When we remember
that the object, whatever it is, is not a mere
plane surface Gas one is so apt to conceive in
regarding a phenomenon of the sort), but
surrounds the sun on every side, we begin to
recognize the enormous volume which it
occupies. Those radiations whose structure
is SO perplexing are in reality enormous
streams of matter, whether continuous or
discrete remains yet to be determined.
These streams, too, are not necessarily
directed towards or from the sun, as one is
apt to suppose FROM their ordinary aspect.
1t is not even probable that they are SO stu
ated, since observers of repute have noticed
that the radiations of the corona are not SYM
nnetrical.
Is it safe to hazard a guess as to the real
nature of the corona, when q few months
may afford positive information respecting
its structure Let us consider what we know
already. 1t has sometimes happened that
astronomers have remained in doubt respect
ing problem whose solution was in reality
in their hands. Galileo was content to remain
perplexed by the strange changes of Saturns
appearance, when it was possible for him to
have anticipated by simple reasoning the dis
covery Of the real nature of the planets ap-
pendage. The predecessors of Sir w. Her
Schel suffered discovery after discovery to
escape them, because they would not be at
the pains to discuss in full their own observa-
tions. The wonderful success Of that great
astronomer was due to his appreciation of the
fact that observations can only be fruitful
when submitted to scrutiny and analysis. 1t
appears to us that the observations already
made upon the corona only require careful
consideration to reveal with tolerable distinct
ness the real nature of this object.
Setting aside the theories which associate
the corona with the moon or with our own
atmosphere, as altogether untenable in the
face of recent discoveries, let us inquire
whether we have any reason to believe that
the portion of space apparently occupied by
the corona is really tenanted by material SUBJ
stance. We cannot suppose that a solar at
mosphere of any sort occupies this region.
For it is incredible that objects of such
nature as the colored prominences-fames
thousands of miles in height-should exist at
the bottom of an atmosphere whose depth
must be estimated by hundreds of thousands
of miles, and which would be subject also to
the enormous attractive energies of the sum s
mass. If our own atmosphere, with a pro-
bable depth of about hundred miles, and
attracted only by the relatively insignificant
forces of terrestrial gravity, is yet capable of
exerting pressure of nearly ton on every
square foot of surface, how inconceivably
vast would be the pressure of an atmosphere
thousands of times as deep (even supposing
the visible bounds of the corona to indicate
its true limits), and attracted by the sun, at
whose surface four of our pounds would
weigh hundred-weight!
The material particles, then, which form
the corona must be of such nature as not to
press towards the sun. In other words, they
must travel around him. AS to the nature of
these motions, we are led by the irregular ap-
Dearance of the corona to believe that the