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Page 25
[Page 80]
[Illustration: Fig. 31.--Zodiacal Light.]
We might say with evident truth that the far-off planets are a
part of the sun, since the space they traverse is filled with the
power of that controlling king; not only with light, but also with
gravitating power.
But come to more ponderable matters. If we look [Page 81] into our
western sky soon after sunset, on a clear, moonless night in March
or April, we shall see a dim, soft light, somewhat like the
milky-way, often reaching, well defined, to the Pleiades. It is
wedge-shaped, inclined to the south, and the smallest star can
easily be seen through it. Mairan and Cassini affirm that they have
seen sudden sparkles and movements of light in it. All our best
tests show the spectrum of this light to be continuous, and
therefore reflected; which indicates that it is a ring of small
masses of meteoric matter surrounding the sun, revolving with it and
reflecting its light. One bit of stone as large as the end of one's
thumb, in a cubic mile, would be enough to reflect what light we see
looking through millions of miles of it. Perhaps an eye sufficiently
keen and far away would see the sun surrounded by a luminous disk,
as Saturn is with his rings. As it extends beyond the earth's orbit,
if this be measured as a part of the sun, its diameter would be
about 200,000,000 miles.
Come closer. When the sun is covered by the disk of the moon at
the instant of total eclipse, observers are startled by strange
swaying luminous banners, ghostly and weird, shooting in changeful
play about the central darkness (Fig. 32). These form the corona.
Men have usually been too much moved to describe them, and have
always been incapable of drawing them in the short minute or two
of their continuance. But in 1878 men travelled eight thousand
miles, coming and returning, in order that they might note the
three minutes of total eclipse in Colorado. Each man had his work
assigned to him, and he was drilled to attend to that and nothing
else. Improved instruments were put into his [Page 82] hands, so
that the sun was made to do his own drawing and give his own picture
at consecutive instants. Fig. 33 is a copy of a photograph of the
corona of 1878, by Mr. Henry Draper. It showed much less
changeability that year than common, it being very near the time of
least sun-spot. The previous picture was taken near the time of
maximum sun-spot.
[Illustration: Fig. 32.--The Corona in 1858, Brazil.]
It was then settled that the corona consists of reflected light,
sent to us from dust particles or meteoroids swirling in the vast
seas, giving new densities and [Page 83] rarities, and hence this
changeful light. Whether they are there by constant projection, and
fall again to the sun, or are held by electric influence, or by
force of orbital revolution, we do not know. That the corona cannot
be in any sense an atmosphere of any continuous gas, is seen from
the fact that the comet of 1843, passing within 93,000 miles of the
body of the sun, was not burned out of existence as a comet, nor in
any perceptible degree retarded in its motion. If the sun's diameter
is to include the corona, it will be from 1,260,000 to 1,460,000
miles.
[Illustration: Fig. 33.--The Corolla in 1878, Colorado.]
[Page 84] Come closer still. At the instant of the totality of the
eclipse red flames of most fantastic shape play along the edge of
the moon's disk. They can be seen at any time by the use of a
proper telescope with a spectroscope attached. I have seen them
with great distinctness and brilliancy with the excellent
eleven-inch telescope of the Wesleyan University. A description of
their appearance is best given in the language of Professor Young,
of Princeton College, who has made these flames the object of most
successful study. On September 7th, 1871, he was observing a large
hydrogen cloud by the sun's edge. This cloud was about 100,000
miles long, and its upper side was some 50,000 miles above the
sun's surface, the lower side some 15,000 miles. The whole had the
appearance of being supported on pillars of fire, these seeming
pillars being in reality hydrogen jets brighter and more active
than the substance of the cloud. At half-past twelve, when
Professor Young chanced to be called away from his observatory,
there were no indications of any approaching change, except that
one of the connecting stems of the southern extremity of the cloud
had grown considerably brighter and more curiously bent to one
side; and near the base of another, at the northern end, a little
brilliant lump had developed itself, shaped much like a summer
thunderhead.
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