Auroræ: Their Characters and SpectraCapron, J. Rand
History
Auroræ: Their Characters and Spectra
Capron, J. Rand
Auroras
If both kinds of light appear at the same time, the second while passing
over the first dims it. If the second class is watched into daylight,
they appear as dirty misty clouds that suddenly form and disappear
without the spectator being able to say where they come from or where
they go to, or as a hazy mist over a portion of the sky, that suddenly
appears and disappears, or as misty rays proceeding from a point in the
horizon. Generally, when these clouds occur, there is a bank of black
clouds to the westward.
[Sidenote: Season since October 1876 prolific in auroric light.]
Mr. Kinahan then speaks of the season as having been prolific in auroric
light, as there had been few nights since the 1st October then last
(1876) in which they did not appear. On many occasions they were late
in the night, being very common and brilliant during the dark days of
December, a few hours before dawn (about 5 o’clock). Each time there was
a fine day they appeared also, and the weather broke again.
[Sidenote: Mr. J. Allan Broun questions nature of these lights, as Aurora
is seldom seen at 5 A.M. in this country. On 77 occasions seen only twice
so early. Season was of marked infrequency elsewhere.]
Mr. Jno. Allan Broun refers to this graphic account of Mr. Kinahan’s,
and concludes there must have been some mistake as to the nature of
these “auroric lights,” as the Aurora Borealis is very rarely seen at
5 A.M. in this country. In the years 1844 and 1845, during which the
Aurora was sought for at Makerstown every hour of the night, it was
observed in 77 nights on an average of nearly three hours each night;
but it was seen only twice so early, and that with a bright or brilliant
Aurora, which remained during five hours on the first occasion, and
from 6 P.M. to 6 A.M. on the second. Parts of the phenomenon seen by
Mr. Kinahan, Mr. Broun also could not say he had ever seen; and if Mr.
Kinahan’s observations could have been confirmed it would have been most
important, especially as made so frequently at the epoch of minimum.
The description is in many respects a sufficiently recognizable one of
auroral discharges; but the frequent appearance in early morning is
certainly unusual, and few if any Auroræ seem to have been recorded as
appearing elsewhere in Great Britain during the time which Mr. Kinahan
refers to as so prolific (see, however, Dr. Allnatt’s, _antè_, p. 24). In
fact, the season in question was one of marked infrequency (see English
Arctic Expedition Report, _antè_, p. 26). Mr. Buchan furnished Mr. Broun
with a note of Auroræ seen in the stations of the Scottish Meteorological
Society during the year 1876, and they were 42 in number, 26 in the first
half, and 16 in the second half of the year. The greater part were seen
in the most northerly stations, including the Orkney, Shetland, and Faroe
Islands, and only 9 south of the Forth.
_Luminous Arch._
[Sidenote: Luminous arch, Sept. 11, 1814. Height above horizon 6 to 9
miles.]
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