The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-04-16

AURORA ROREALIS.
Las Night Witnesses n MAGNIFICENT Exhibition
Of the Northern Lights,


sAed display OF the aurora boreas which has taken
place since the great exhibition OF 1859 was visible
pcarance frequently seen near the horizon as diu-
ave nght IKE the morning twilight, whence 1t has
Hemisphere 1t is usually termed aurora 6orealts
because II is chiefly seen in the north. similar
where it is called the aurorc austraiis
Bach OF them may with greater proprtety be
an infinite variety Of appearances but they may
generally be referred to one of the following casses
sress nf Gav senon1 An mar arch @ ofS somewba in in
the form OF rainbow. Third, Slender, luminous
beams or columns, well defined, and often OF bright
aame, formed by luminous beams shooting up stimuli
taneousy from nearly every part of the horizon, and
converging in point little south of the zenith.
Fifth Waves or flashes of light The duration OF
auroras is very variable. Some last only an hour
two, others last all night, and occasionally they ap
pear two successive nights, under circun-
stances which lead us to believe
the sun, might be seen unnterruptedly for
thrty-six or forty-elght hours. Auroras are char
bright one has faded away, and almost wholly disap-
peared, it is common for it to revive, to rival
and often surpass its first magnnCence Their
coors very variable. II the aurora be faint, its
light is usually white or pale yellow When It is
brilliant, the sky exhibits at the same time great
variety OF tnts Some portions OF the sky are nearly
white, but with tinge of emerald green other por-
tons are of pale yellow or straw color; others
tinged with rosy hue; while others have crimson
hue, which sometimes deepens to a blood red.
These colors are ever varying in position
and intensity. AurOraS are sometimes observed
simultaneously over large portions OF the globe, one
b. ing visible at the same time in South America
and New Holland. In the United States an aurora
10 uniformly preceded by q haZy or cloudy appear
of the sky, particularly in the neghbOrhood Of
the northern horizon When the display commences,
this hazy portion OF the sky assumes the form Of
dark bank segment Of a circle in the north, rising
ordinarily to the height of from to 10 degrees The
dark segment is bounded by luminous arc, whose
breadth varies from half degree to or two de-
grees II the aurora becomes brilliant, other arcs
tp 10TH at greater, e9yaIon, someumes passing
less active its beams become less lumi-
nous their edges become more di1use; they
increase in breadth, while they diminish in length,
and assume the appearance of luminous clouds.
From multitude of observations, it is concluded
that the aurora seldom appears at elevation less
than about fortyve miles above the earts surface,
and that it frequently extends upward to an eeva-
wel-defned border, are generally less than one hun
dred miles in height. There is no satisfactory evil
though that fact has been asserted AurOras appear
at ali hours Of the night and in every month Of the
year. They are ordinarily accompanied by
considerable disturbance of the magnetic
needle, and the effect increases with their bril-
lancy and extent AurOra beams cause disturb
ance of the needle, particularly when the beams
themselves are in active motion. Auroral waves or
nashes-especially if they extend to the zenith
violent agitation of the needle, consisting OF
An irregular oscillation on each side OF its mean
position. They also exert a remarkable influence
upon the wires Of the electric telegraph. During the
prevalence of brilliant ones the telegraph lines
generally become unmanageabe. The aurora de-
velOps electric currents upon the wires, and hence
results motion of the telegraph Instruments similar
70 that which is employed in teegraphing, and the
movement being frequent and irregular, ordinarily
renders 1t impossible to transmit ntelligble
signals During several remarkable auroras, how
ever, and the one of last night included, the
currents Of electricity on the telegraph wires have
been so steady and powerful that they have been
used for teegraphc purposes as u substitute for Il
vOltaic battery; that is, teegraphic messages have
been transmitted from the auroral influence alone.
Some have asserted that the aurora is caused by
nebulous matter falling into our atmosphere, but
this theory is generally discredited. In fact, the
aurOral light Is electric light. This proven by the
erect Of the aurora upon the telegraph wires. Be-
Sides the Colors of the aurora the same those
OF ordinary electricity passed through rarecd air.
The auroral beams simply illumined spaces
caused by the flow OF electricity through the upper
regions of the atmosphere.
The auroral display of last night commenced
shortly after dark and continued until long after 70
O'Clock. IL varied from former in this respect,
That its greatest brilliancy observable at the
eastern and western eXtremetes OF the horizon.
considerable portion of the time the whole northern
half of the hemisphere was most brilliantly lumi-
mated.
Streaks of red blue, green and white lights shot
ap in rapid succession from the horizon to the
to streams OF spray thrown from innumerabe fire
engines, and tinged with different colors. The
heavens at different periods during the night fairly
suyered with the rays of light that shot forth in ali
directions. and broad belts of white light stretched
directly over head from one extremity OF the sky to
the other.
The phenomenon was witnessed by hundreds OF
persons, who gathered at the street corners, and
who enjoyed the free show greatly. During the pre-
Vaence of the display, the air was so completely
charged with electricity that the different telegra-
phic companies dispensed with the use OF their bat
teries at either end of their lmcS and worked tnelf
wires only by the electricity in the air produced by
the aurora borealis.
number OF observations were made upon it by
scientific gentlemen, with what result we have not
yet learned
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