Evening star. [volume] (Washington, D.C.) 1854-1972, 1892-02-15
SCIENTIFICALLY OBSERVED.

SCIENTIFICALLY OBSERVED.
The magnificent spectacle was scientifically
observed at the University of Michigan in Ann
Arbor. Astronomical Director W. ]. Hussey of
that institution wires the result as follows:
The brilliant rose-red aurora visible tonight
was not altogether unexpected. In general
way auroras have been predicted for about this
time. Saturday nights display naturally fol-
lows the appearance Of the great sun spot
which has been visible during the past week
Other aurorial displays may be expected in the
near future"
An astronomer chatted entertainingly with a
STAR reporter this morning upon the general
subject of auroras. He said:
AN ASTRONOMER TALKS ON THE PHENOMENON.
Little is known as to the cause of the aurora
polaris. or the aurora borealis, as it is generally
called here. There is similar phenomenon at
the south pole called the aurora austraIis. Evil
IDENTIFY il Is of electric origin. Its arch ALWAYS
appears to span the earths magnetic poles,
which. as Is well known to science do not ex-
actly coincide with the poles of revolution. At
Intervals OF about eleven years the earth is sub
Ject to violent magnetic storms and it il pre-
clsely during these periods that auroras occur
most frequently; and no auroras are ever seen
without the simultaneous occurrence of a mag
netic storm. and during the auroral flashes the
needle Is subject to violent and irregular agita-
ton.
disturbances take place when the dark spots on
the sun exist In the greatest number. These
spots likewise reach a maximum every eleven
years, while there is another longer period of
about sixty years between maxima of all these
phenomena, at which intervals thew have the
grandest displays. The constant direction of
the arch OF the aurora, the fact that its radial
streamers all point toward the magnetic poles
and its disturbing action on the magnetic
needle seem to prove that it is due to electric
currents in the higher regions of the atmos-
phere. Franklin believed that the warm
streams OF air and vapor rising at the equatorial
regions are charged with electricity due to the
evaporation of water, and that when they reach
the polar regions there is a discharge to the
earth.
DE la RIvE's THEORY
''De la Rive believed that the sun separated
the positive and negative electricites in equa-
torial regions by inductive action. and that the
discharge takes place as mentioned above. At
the height at which these aurora occur which
Is generally between so and 500 miles above
the earth, the atmosphere Is very rare. and the
soft, rich tints. situations and streamers and
wayy motions observed are exactly like those
easily obtained by passing an electric current
through partially exhausted glass tubes
containing highly rareied air and other
gases. This shows very clearly the cleo
trical nature OF the phenomenon. and these
currents are doubtless OF secondary origin
induced by disturbances in the earth magnet
ism. which are themselves due to similar dis
turbances on a larger scale in the sum- which
produces the dark spots. Such a spot is now
visible on the eastern limb Of the sun. With
the aid Of smoked glass any one may observe
this great cnasm which is a vast cavity in the
photosphere of the sun These cavities are
composed Of two parts, the umbra and penum-
bra. and they are sometimes SO large that our
earth might be dropped into one without dis
turbing the feathery flaments Of the penum-
bra"