seen on Oct. 13, 1876. It looked at first, in the telescope, like two
spots without any connection; then, as vision improved and higher
powers were employed, the two were seen to have a subtle bond of union,
and each to be filled with the most curious foliage-forms, which I
could only indicate in the few moments that the good definition lasted.
The reader may be sure, I think, that there is no exaggeration of the
curious shapes of the original; for I have been so anxious to avoid the
overstatement of curvature that the error is more likely to be in the
opposite direction.
We must conclude that the question as to the cyclonic hypothesis cannot
yet be decided, though the probabilities from telescopic evidence
at present seem to me on the whole in favor of M. Faye’s remarkable
theory, which has the great additional attraction to the student that
it unites and explains numerous other quite disconnected facts.
Turning now to the other solar features, let us once more consider
the sun as a whole. Fig. 27 is a photograph taken from a part of the
sun near its edge. We notice on it, what we see on every careful
delineation of the sun, that its general surface is not uniformly
bright, but that it grows darker as we approach the edge, where it
is marked by whiter mottlings called faculæ, “something in the sun
brighter than the sun itself,” and looking in the enlarged view which
we present of one of them (Fig. 28), as if the surface of partly
cooled metal in a caldron had been broken into fissures showing the
brighter glow beneath. These “faculæ,” however, are really above the
solar surface, not below it, and what we wish to direct particular
attention to is that darkening toward the edge which makes them visible.
[Illustration: FIG. 28.--FACULA. (FROM A DRAWING BY CHACORNAC.)]
This is very significant, but its full meaning may not at first be
clear. It is owing to an atmosphere which surrounds the sun, as the
air does the earth. When we look horizontally through our own air, as
at sunrise and sunset, we gaze through greater thicknesses of it than
when we turn our eyes to the zenith. So when we look at the edge of
the sun, the line of sight passes through greater depths of this solar
atmosphere, and it dims the light shining behind it more than at the
centre, where it is thin.
This darkening toward the edge, then, means that the sun has an
atmosphere which tempers its heat to us. Whatever the sun’s heat
supply is within its globe, if this atmosphere grow thicker, the
heat is more confined within, and our earth will grow colder; if the
solar atmosphere grow thinner, the sun’s energy will be expended more
rapidly, and our earth will grow hotter. This atmosphere, then, is in
considerable part, at least, the subject of the action of the spots;
this is what they are supposed to carry down or to spout up.
We shall return to the study of it again; but what I want to point out
now is that the temperature of the earth, and even the existence of man
upon it, depends very much upon this, at first sight, insignificant
phenomenon. What, then, is the solar atmosphere? Is it a permanent
thing? Not at all. It is more light and unsubstantial than our own
air, and is being whirled about by solar winds as ours toss the dust
of the streets. It is being sucked down within the body of the sun by
some action we do not clearly understand, and returned to the surface
by some counter effect which we comprehend no better; and upon this
imperfectly understood exchange depends in some way our own safety.
There used to be recorded in medical books the case of a boy who, to
represent Phœbus in a Roman mask, was gilded all over to produce the
effect of the golden-rayed god, but who died in a few hours because,
all the pores of the skin being closed by the gold-leaf, the natural
circulation was arrested. We can count with the telescope millions of
pores upon the sun’s surface, which are in some way connected with the
interchange which has just been spoken of; and if this, his own natural
circulation, were arrested or notably diminished, we should see his
face grow cold, and know that our own health, with the life of all the
human race, was waiting on his recovery.
II.
THE SUN’S SURROUNDINGS.
As I write this, the fields glitter with snow-crystals in the winter
noon, and the eye is dazzled with a reflection of the splendor which
the sun pours so fully into every nook that by it alone we appear to
see everything.
Yet, as the day declines, and the glow of the sunset spreads up to the
zenith, there comes out in it the white-shining evening star, which
not the light, but the darkness, makes visible; and as the last ruddy
twilight fades, not only this neighbor-world, whose light is fed from
the sunken sun, but other stars appear, themselves self-shining suns,
which were above us all through the day, unseen because of the very
light.
As night draws on, we may see the occasional flash of a shooting-star,
or perhaps the auroral streamers spreading over the heavens; and
remembering that these will fade as the sun rises, and that the nearer
they are to it the more completely they will be blotted out, we infer
that if the sun were surrounded by a halo of only similar brightness,
this would remain forever invisible,--unless, indeed, there were
some way of cutting off the light from the sun without obscuring its
surroundings. But if we try the experiment of holding up a screen which
just conceals the sun, nothing new is seen in its vicinity, for we are
also lighted by the neighboring sky, which is so dazzlingly bright with
reflected light as effectually to hide anything which may be behind it,
so that to get rid of this glare we should need to hang up a screen
_outside_ the earth’s atmosphere altogether.
[Illustration: FIG. 29.--LUNAR CONE SHADOW.]
Nature hangs such a screen in front of the earth when the moon passes
between it and the sun; but as the moon is far too small to screen
all the earth completely, and as so limited a portion of its surface
is in complete shadow that the chances are much against any given
individual’s being on the single spot covered by it, many centuries
usually elapse before such a _total_ eclipse occurs at any given point;
while yet almost every year there may be a partial eclipse, when, over
a great portion of the earth at once, people may be able to look round
the moon’s edge and see the sunlight but partly cut off. Nearly every
one, then, has seen a partial eclipse of the sun, but comparatively few
a total one, which is quite another thing, and worth a journey round
the world to behold; for such a nimbus, or glory, as we have suggested
the possibility of, does actually exist about the sun, and becomes
visible to the naked eye on the rare occasions when it is visible at
all, accompanied by phenomena which are unique among celestial wonders.
The “corona,” as this solar crown is called, is seen during a total
eclipse to consist of a bright inner light next the invisible sun,
which melts into a fainter and immensely extended radiance (the writer
has followed the latter to the distance of about ten million miles),
and all this inner corona is filled with curious detail. All this is
to be distinguished from another remarkable feature seen at the same
time; for close to the black body of the moon are prominences of a
vivid crimson and scarlet, rising up like mountains from the hidden
solar disk, and these, which will be considered later, are quite
distinct from the corona, though seen on the background of its pearly
light.
To understand what the lunar screen is doing for us, we may imagine
ourselves at some station outside the earth, whence we should behold
the moon’s shadow somewhat as in Fig. 29, where we must remember that
since the lunar orbit is not a circle, but nearly an ellipse, the
moon is at some times farther from the earth than at others. Here the
extremity of its shadow is represented as just touching the surface of
the globe, while it is evident that if the moon were at its greatest
distance, its shadow might come to a point before reaching the earth at
all. We speak, of course, only of the central cone of shade; for there
is an outer one, indicated by the faint dotted lines, within whose much
more extended limits the eclipse is partial, but with the latter we
have at present nothing to do. The figure however, for want of room,
is made to represent the proportions incorrectly, the real ones of the
shadow being actually something like those of a sewing-needle,--this
very long attenuated shadow sometimes, as we have just said, not
reaching the earth at all, and when it does reach it, covering at the
most a very small region indeed. Where this point touches, and wherever
it rests, we should, in looking down from our celestial station, see
that part of the earth in complete shadow, appearing like a minute dark
spot, whose lesser diameter is seldom over a hundred and fifty miles.
The eclipse is total only to those inhabitants of the earth within
the track of this dark spot, though the spot itself travels across
the earth with the speed of the moon in the sky; so that if it could
leave a mark, it would in a few hours trace a dark line across the
globe, looking like a narrow black tape curving across the side of the
world next the sun. In Fig. 30, for instance, is the central track of
the eclipse of July 29, 1878, as it would be visible to our celestial
observer, beginning in Alaska in the forenoon, and ending in the Gulf
of Mexico, which it reached in the afternoon. To those on the earth’s
surface within this shadow it covered everything in view, and, for
anything those involved in it could see, it was all-embracing and
terrible, and worthily described in such lines as Milton’s,--
“As when the sun ...
In dim eclipse, disastrous twilight sheds
On half the nations, and with fear of change
Perplexes monarchs.”
We may enjoy the poet’s vision; but here, while we look down on
the whole earth at once, we must admit that the actual area of the
“twilight” is very small indeed. Within this area, however, the
spectacle is one of which, though the man of science may prosaically
state the facts, perhaps only the poet could render the impression.
We can faintly picture, perhaps, how it would seem, from a station
near the lunar orbit, to see the moon--a moving world--rush by with a
velocity greater than that of the cannon-ball in its swiftest flight;
but with equal speed its shadow actually travels along the earth. And
now, if we return from our imaginary station to a real one here below,
we are better prepared to see why this flying shadow is such a unique
spectacle; for, small as it may be when seen in relation to the whole
globe, it is immense to the observer, whose entire horizon is filled
with it, and who sees the actual velocity of one of the heavenly
bodies, as it were, brought down to him.
The reader who has ever ascended to the Superga, at Turin, will recall
the magnificent view, and be able to understand the good fortune of
an observer (Forbes) who once had the opportunity to witness thence
this phenomenon, and under a nearly cloudless sky. “I perceived,” he
says, “in the southwest a black shadow like that of a storm about to
break, which obscured the Alps. It was the lunar shadow coming toward
us.” And he speaks of the “stupefaction”--it is his word--caused by
the spectacle. “I confess,” he continues, “it was the most terrifying
sight I ever saw. As always happens in the cases of sudden, silent,
unexpected movements, the spectator confounds real and relative motion.
I felt almost giddy for a moment, as though the massive building under
me bowed on the side of the coming eclipse.” Another witness, who had
been looking at some bright clouds just before, says: “The bright cloud
I saw distinctly put out like a candle. The rapidity of the shadow, and
the intensity, produced a feeling that something material was sweeping
over the earth at a speed perfectly frightful. I involuntarily listened
for the rushing noise of a mighty wind.”
[Illustration: FIG. 30--TRACK OF LUNAR SHADOW.]
Each one notes something different from another at such a time; and
though the reader will find minute descriptions of the phenomena
already in print, it will perhaps be more interesting if, instead of
citations from books, I invite him to view them with me, since each can
tell best what he has personally seen.
[Illustration: FIG. 31.--INNER CORONA ECLIPSE OF 1869. FROM SHELBYVILLE
PHOTOGRAPH. (ROYAL ASTRONOMICAL SOCIETY’S MEMOIRS.)]
I have witnessed three total eclipses, but I do not find that
repetition dulls the interest. The first was that of 1869, which
passed across the United States and was nearly central over Louisville.
My station was on the southern border of the eclipse track, not very
far from the Mammoth Cave in Kentucky, and I well remember that
early experience. The special observations of precision in which I
was engaged would not interest the reader; but while trying to give
my undivided attention to these, a mental photograph of the whole
spectacle seemed to be taking without my volition. First, the black
body of the moon advanced slowly on the sun, as we have all seen it do
in partial eclipses, without anything noticeable appearing; nor till
the sun was very nearly covered did the light of day about us seem
much diminished. But when the sun’s face was reduced to a very narrow
crescent, the change was sudden and startling, for the light which fell
on us not only dwindled rapidly, but became of a kind unknown before,
so that a pallid appearance overspread the face of the earth with an
ugly livid hue; and as this strange wanness increased, a cold seemed to
come with it. The impression was of something _unnatural_; but there
was only a moment to note it, for the sun went out as suddenly as a
blown-out gas-jet, and I became as suddenly aware that all around,
where it had been, there had been growing into vision a kind of ghostly
radiance, composed of separate pearly beams, looking distinct each from
each, as though the black circle where the sun once was, bristled with
pale streamers, stretching far away from it in a sort of crown.
This was the mysterious corona, only seen during the brief moments
while the shadow is flying overhead; but as I am undertaking to recall
faithfully the impressions of the instant, I may admit that I was at
the time equally struck with a circumstance that may appear trivial
in description,--the extraordinary globular appearance of the moon
herself. We all know well enough that the moon is a solid sphere, but
it commonly _looks_ like a bright, flat circle fastened to the concave
of the starry vault; and now, owing to its unwonted illumination, the
actual rotundity was seen for the first time, and the result was to
show it as it really is,--a monstrous, solid globe, suspended by some
invisible support above the earth, with nothing apparent to keep it
from tumbling on us, looking at the moment very near, and more than
anything else like a gigantic black cannon-ball, hung by some miracle
in the air above the neighboring cornfield. But in a few seconds all
was over; the sunlight flashed from one point of the moon’s edge and
then another, almost simultaneously, like suddenly kindled electric
lights, which as instantly flowed into one, and it was day again.
[Illustration: FIG. 32.--SKETCH OF OUTER CORONA, 1869. (U. S. COAST
SURVEY REPORT.)]
I have spoken of the “unnatural” appearance of the light just before
totality. This is not due to excited fancy, for there is something
so essentially different from the natural darkness of twilight, that
the brute creation shares the feeling with us. Arago, for instance,
mentions that in the eclipse of 1842, at Perpignan, where he was
stationed, a dog which had been kept from food twenty-four hours was,
to test this, thrown some bread just before “totality” began. The
dog seized the loaf, began to devour it ravenously, and then, as the
appearance already described came on, he dropped it. The darkness
lasted some minutes, but not till the sun came forth again did the poor
creature return to the food. It is no wonder, then, that men also,
whether educated or ignorant, do not escape the impression. A party of
the courtiers of Louis XV. is said to have gathered round Cassini to
witness an eclipse from the terrace of the Paris observatory, and to
have been laughing at the populace, whose cries were heard as the light
began to fade; when, as the unnatural gloom came quickly on, a sudden
silence fell on them too, the panic terror striking through their
laughter. Something common to man and the brute speaks at such times,
if never before or again; something which is not altogether physical
apprehension, but more like the moral dismay when the shock of an
earthquake is felt for the first time, and we first know that startling
doubt, superior to reason, whether the solid frame of earth is real,
and not “baseless as the fabric of a vision.”
But this is appealing for illustration to an experience which most
readers have doubtless been spared,[2] and I would rather cite the
lighter one of our central party that day, a few miles north of me,
at Shelbyville. In this part of Kentucky the colored population was
large, and (in those days) ignorant of everything outside the life of
the plantation, from which they had only lately been emancipated. On
that eventful 8th of August they came in great numbers to view the
enclosure and the tents of the observing party, and to inquire the
price of the show. On learning that they might see it without charge
from the outside, a most unfavorable opinion was created among them as
to the probable merits of so cheap a spectacle, and they crowded the
trees about the camp, shouting to each other sarcastic comments on the
inferior interest of the entertainment. “Those trees there,” said one
of the observers to me the next day, “were black with them, and they
kept up their noise till near the last, when they suddenly stopped, and
all at once, and as ‘totality’ came, we heard a wail and a noise of
tumbling, as though the trees had been shaken of their fruit, and then
the boldest did not feel safe till he was under his own bed in his own
cabin.”
[2] This was written before the “Charleston earthquake”
occurred.
[Illustration: FIG. 33.--TACCHINI’S DRAWING OF CORONA OF 1870.
(SECCHI’S “LE SOLEIL.”)]
It is impossible to give an exact view of what our friends at
Shelbyville saw, for no drawings made there appear to have been
preserved, and photography at that time could only indicate feebly
the portion of the corona near the sun where it is brightest. Fig.
31 is a fac-simile of one of the photographs taken on the occasion,
which is interesting perhaps as one of the early attempts in this
direction, for comparison with later ones; but as a picture it is very
disappointing, for the whole structure of the outer corona we have
alluded to is missed altogether, the plate having taken no impression
of it.
A drawing (Fig. 32) made by another observer, Mr. M’Leod, at
Springfield, represents more of the outer structure; but the reader
must remember that all drawings must, in the nature of the case (since
there are but two or three minutes to sketch in), be incomplete,
whatever the artist’s skill.
[Illustration: FIG. 34.--WATSON’S NAKED-EYE DRAWING OF CORONA OF 1870.
(U. S. COAST SURVEY REPORT.)]
Up to this time it was still doubtful, not only what the corona
was, but where it was; whether it was a something about the sun or
moon, or whether, indeed, it might not be in our own atmosphere. The
spectroscopic observations of Professors Young and Harkness at this
same eclipse of a green line in its spectrum, due to some glowing
gas, showed conclusively that it was largely, at any rate, a solar
appendage, and partly, at least, self-luminous; and these and other
results having awakened general discussion among astronomers in Europe
as well as at home, the United States Government sent an expedition,
under the direction of the late Professor Pierce, to observe an eclipse
which in the next year, on Dec. 8, 1870, was total in the south of
Spain. There were three parties; and of the most western of these,
which was at Xeres under the charge of Professor Winlock, I was a
member.
[Illustration: FIG. 35.--PHOTOGRAPH SHOWING COMMENCEMENT OF OUTER
CORONA.
(ROYAL ASTRONOMICAL SOCIETY’S MEMOIRS.)]
The duration of totality was known beforehand. It would last two
minutes and ten seconds, and to secure what could be seen in this brief
interval we crossed the ocean. Our station was in the midst of the
sherry district, and a part of the instruments were in an orange-grove,
where the ground was covered with the ripe fallen fruit, while the
olive and vine about us in December reminded us of the distance we had
come to gather the results of so brief an opportunity.
To prepare for it, we had all arrived on the ground some weeks
beforehand, and had been assiduously busy in installing the
apparatus in the observing camp, which suggested that of a small
army, the numerous instruments, some of them of considerable
size,--equatorials, photographic apparatus, polariscopes, photometers,
and spectroscopes,--being under tents, the fronts of which could be
lifted when the time came for action.
To the equatorial telescopes photographic cameras are attached instead
of the eye-pieces, in the hope that the corona may be made to impress
itself on the plate instead of on the eye. The eye is an admirable
instrument itself, no doubt; but behind it is a brain, perhaps
overwrought with excitement, and responding too completely to the
nervous tension which most of us experience when those critical moments
are passing so rapidly. The camera can see far less of the corona than
the man, _but it has no nerves_, and what it sets down we may rely on.
At such a time each observer has some particular task assigned to
him, on which, if wise, he has drilled himself for weeks beforehand,
so that no hesitation or doubt may arise in the moment of action; and
his attention is expected to be devoted to this duty alone, which may
keep him from noting any of the features which make the occasion so
impressive as a spectacle. Most of my own particular work was again of
a kind which would not interest the reader.
Apart from this, I can recall little but the sort of pain of
expectation, as the moment approached, till within a minute before
totality the hum of voices around ceased, and an utter and most
impressive silence succeeded, broken only by a low “Ah!” from the group
without the camp, when the moment came. I remember that the clouds,
which had hung over the sun while the moon was first advancing on its
body, cleared away before the instant of totality, so that the last
thing I saw was a range of mountains to the eastward still bright
in the light; then, the next moment, the shadow rushed overhead and
blotted out the distant hills, almost before I could turn my face to
the instrument before me.
[Illustration: FIG. 36.--ECLIPSE OF 1857, DRAWING BY LIAIS. (ROYAL
ASTRONOMICAL SOCIETY’S MEMOIRS.)]
The corona appeared to me a different thing from what it did the year
before. It was apparently confined to a pearly light of a roughly
quadrangular shape, close to the limb of the sun, broken by dark rifts
(one of which was a conspicuous object); while within, and close to
the limb, was what looked like a mountain rising from the hidden sun,
of the color of the richest tint we should see in a rose-leaf held up
against the light, while others were visible of an orange-scarlet.
After a short scrutiny I turned to my task of analyzing the nature of
the white light.