Year: 1871

ALTHOUGH many ancient writers allude
to appearances in the sky which, there is
no doubt, were identical with the aurora,
We have notany very accurate descriptions
the phenomena having been regarded from
superstitious rather than a scientific
point of view. The first of these displays
of which we have careful and scientific
account is one that occurred A. ID. 1860 !;
but the particulars were not published till
ninety years afterward, when they ap-
peared in book called "a Description of
Meteors." In 1921 the name of Aurora
Borealis was given to this phenomenon by
GassenGi, the French philosopher, on the
occasion of remarkable display visible
over a great part of Europe. None seems
to have been observed after this till the
year 1907; but during the last century it
has been by no means uncommon.


1t occurs generally in the spring or
autumn, particularly after dry year In
the arctic regions. however, it is the usual
accompaniment of clear winters night,
and is familiar to the inhabitants even of
the Shetland Isles. Lights of similar
character have been observed toward the
south pole. Mr.. Foster, in voyage with
Captain Cook, had an opportunity of OBJ
serving the Aurora Australis, as it has been
termed, and thus describes its appearance ::
1t consisted of long columns of clear
white light, shooting up from the horizon
to the eastward almost to the zenith, and
gradually spreading over the whole south
ern part of the sky. These columns were
sometimes bent sideways at their upper ex
tremeties, and though in most respects
similar to the northern lights of our hem
isphere, yet differed from them in being
always of whitish color, whereas ours as
sumo various tints, especially those of
fiery and purple hue


1t is, however, in the northern hemis-
phere that there have been most opportu
mites of taking minute observations of
this phenomenon, and it is from these that
we are able to form some idea of the natu
raj operations to which it owes its exist
ence. The flashes of light which consti-
tute the aurora are now generally allowed
to be within the region of the terrestrial
atmosphere, though they were at one time
considered to be far beyond it, as it was
thought that they could not otherwise be
visible at such height from the horizon
over such an extended area 1t would ap-
pear, however, that the aurora covers a
would suppose. All is invisible to him
except certain arc, with its flaming and
streaming offshoots. Its visibility has, per-
haps, sone analogy to that of the rainbow,
which, as is well known, appears to two
observers to be of different height, their
positions requiring the light to be reflected
from different parts of the sky to make the
same angles of incidence and reflection
equal in the case of each. There are cir
cumstances attending the auroral phenOm-
ena which may be accepted as proofs of
their electric nature. 1t is supposed that
the lights seen are flashes of electricity
passing through the higher strata of the
atmosphere, which are, of course, highly
rarefied, and an experiment whereby a
stream of electricity is passed through
glass tube, from which the air has been
exhausted, strengthens this view, appear
ances similar to those of the aurora having
been noted.


The position of the arc is observed to
bear remarkable relation to the magnetic
pole: it generally lies east and west, hay
ing its vortex on the magnetic meridian,
but it appears at all times to have the mag
netic pole for its center. The earth cur
rents of electricity, which often interfere
with the working of electric telegraphs,
are most frequent at the time of a display
of the aurora, sometimes causing an entire
stoppage in the working of the wires, un-
| less the electric circuit can, by using
double wires, be rendered independent of
the earth. The magnetic compass is also
affected during the display of an aurora,
and often in places where the latter is in
visible. Sir John Franklin, who made
some minute observations in the arctic re-
gions upon the deviations of the needle,
which are often so slight as to require mi
croscopic examination, stated that the mo-
tions were not sudden; but that after an
aurora, the needle would travel slowly in
a certain direction, and as slowly recover
| its position after several hours. he also
remarked that when the arc was not at
right angles to the meridian, but inclined
/ to east or west, the needle deviated toward
/ that end of the ark which was nearer to
the magnetic pole; after deviation it would
be assisted in recovering its position if an
aurora occurred in a direction opposite to
the former. He observed that when the
arc seemed to be exactly at right angles to
the meridian the needle was generally in
clined to the west. The prevalence oi
pink, violet and blue in tine colors of the
lights seems to confirm the probability
that they result from discharge Of cleo
tricity; and the noise affirmed by some
to have been heard at the Tune OF an
auroral display seems to have resembled
somewhat the cracking sound heard when
sparks are taken from a Leyden-jar, ol
the conductor of an electric machine. The
hearers have compared it TO the sound
made by rubbing one piece of silk on an
other, and the discharge of fireworks
Some, however, including Captains Parry
and Franklin, have affirmed that they