The Portland daily press., 1897-06-29
THE AURORA.


If fireballs were thought miraculous
and portentous in days of yore, what in
depreciation 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 40 days, there were
seen horsenen running in the air, in cloth
of gold, armed with lances, like band
of soldiers; and troops of horsemen in ar
ray encountering and running one
against another, with shaking of shields
and multitude of pixies. and drawing of
swords and casting of darts, and glitter
ing of golden ornaments and harness -
Dire olnens these; and hardly less omi-
nous the aurora seemed to all succeeding
generations that observed it down till
well into the 18th century-as witness the
popular excitement in England in 1716
over the brilliant aurora of that year.
which became famous through HALEY S
description.
But after 1852, when Franklin de-
throned the lightning, all spectacular
meteors came to be regarded as natural
phenomena, the aurora among the rest
Franklin explained the aurora-which
was seen commonly enough in the 18th
century, though only recorded once in the
l7th-as due to the accumulation of cleo
tricity on the surface of polar SHOWS, and
its discharge to the equator through the
upper atmosphere. Erasmus Darwin sug-
gested 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, esti
mating it at about 100 miles, thought the
phenomenon due to magnetism acting on
ferruginous particles in the air, and his
explanation was perhaps the most popu-
lar one at the beginning of the century.
Since then 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 it's exact
nature is as undetermined today as it
was hundred years ago. There has been
no dearth of theories concerning it, how
eer. Blot, who studied it in the Shet-
land Islands in 1917, thought it due to
electrified ferruginous dust, the origin of
which he ascribed to Icelandic volcanoes.
Much more recently the idea of ferrugi-
nous particles has been revived, their
presume DolI1S5 1oCIlDou uOb 10 volcanoes,
but to the meteories constantly being
dissipated in the upper atmosphere. Fer
ruginous 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 phenom-
ena 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
triclty generated at the equator, and pas
sing through upper regions of space, to
enter the earth at the magnetic poles
simply reversing the course which Frank
lin assumed.
The similarity of the auroral light to
that generated in 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
awaits complete calculation For once
even that mystery solver, the spectroscope,
has been baffied, for the line it Sits from
the aurora is not matched by that of any
recognized substance. A like line is
found in the zodiacal light. which though