Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1897-05-28
What Causes the Aurora Bore,
alis?

If fire-balls Meteorites were thought
miraculous and portentous in days of yore,
what Interpretation must needs have been
put upon that vastly more picturesque phe-
nomenon, the aurora! Through all the
city, ;" says the book of Maccabees, "for the
space of almost forty days, there were seen
horsemen running in the air, in cloth of
gold, armed with lances, like a band of
soldiers: and troops % horsemen in array
encountering and running one against an
other, with shaking of shields and multi
tude of pixies and drawing of swords, and
casting of darts and glittering of golden
ornaments and harness. Dire omens
these: and hardly less ominous the aurora
seemed to all succeeding generations that
observed it down till well into the eigh-
teenth century-as witness the popular ex
citement in England in 17l6 over the brill
liant aurora of that year, which became
famous through Halleys description.
But after 1852, when Franklin dethroned
the lightning, all spectacular meteors came
to be regarded as natural phenomena, the
aurora among the rest. Franklin explain
ed the aurora-which was seen commonly
enough in the eighteenth century, though
only recorded once in the seventeenth-as
due to the accumulation of electricity on
the surface of polar SHOWS, and its dis
charge to the equator through the upper
atmosphere Erasmus Darwin suggested
that the luminosity might be due to the
ignition of hydrogen, which was supposed
by many philosophers to form the upper
atmosphere Dalton, who first measured
the height of the aurora, estimating it at
about one hundred miles, thought the phe-
nomenon due to magnetism acting on fer
ruginous particles in the air, and his ex-
PLANTATION was perhaps the most popular one
at the beginning of the century,
Since then a multitude of observers have
studied the aurora but the scientific grasp
has found it as elusive in fact as it seems
to casual observation, and its exact nature
is as undetermined today as it was a hun
bred years ago. There has been no dearth
of theories concerning it, however. Blot,
who studied it in the Shetland Islands in
! 1917, thought it due to electrified ferru-
! ginous dust, the origin of which he ascribed
to Icelandic volcanoes. Much more re-
Gently the idea of ferruginous particles has
been revived, their presence being ascribed
not to volcanoes, but to the meteorites con-
stantly being dissipated in the upper atmos-
phere Ferruginous dust, presumably of
such origin, has been found on the polar
SHOWS. as well as on the SHOWS of mountain
tops. but whether it could produce the phe-
nomena of auroras is at least an open ques-
ton. The prevailing theory of today is
| that the aurora is due to a current of cleo
tricity generated at the equator, and pass
ing through upper regions of space to enter
the cart at the magnetic poles-slmply re-
versing the course which Franklin assumed
The similarity of the auroral light TO that
generated in a vacuum bulb by the passage
of electricity lends support TO the long
standing supposition that the aurora is OF
electrical origin, but the subject still await:
complete elucidation. For once even that
mystery solver, the spectroscope has been
baffied, for the line it shifts from the aurora
is not matched by that of any recognized
substance. A like line is found in the
zodiacal light, it is true, but this is of little
aid, for the zodiacal light, though thought
by some astronomers to be due TO meteor
swarms about the sum- is held to be, on the
whole, as mysterious as the aurora itself.
Whatever the exact nature of the auro
ra, it has long been known to be intimately
associated with the phenomena of terres
trial magnetism. Whenever a brilliant
aurora is visible, the world is sure to be
visited with what Humboldt called a mag
netic storm-a storm" which manifesti
itself to human senses in no way whatso
ever except by DETECTING the magnetic
needle and coniuring with the electric wire
Such magnetic storms are curiously associ
ated also with spots on the sun-just how
no one has explained, though the fact itsel
is unquestioned. Sun-spots, too, seem di
rectly linked with auroras, each of thes'
phenomena passing through periods o
greatest and least frequency in correspond
ing cycles of about eleven years duration
HdrDer'S Magazine for June.