Auroræ: Their Characters and SpectraCapron, J. Rand
History
Auroræ: Their Characters and Spectra
Capron, J. Rand
Auroras
In the first Swedish Expedition, 1868, some remarkable observations were
made on the appearance of luminous beams around the tops of mountains,
which M. Lemström showed by the spectroscope to be of the same nature as
Auroræ.
[Sidenote: Aurora from earth’s surface. Yellow-green line seen.]
On the 1st September, 1868, on the Isle of Amsterdam in the Bay of
Sweerenberg, there was a light fall of snow, and the snowflakes were
observed falling obliquely. All at once there appeared a luminous
phenomenon which, starting from the earth’s surface, shot up vertically,
cutting the direction of the falling snowflakes, and this appearance
lasted for some seconds. On examination with a spectroscope the
yellow-green line was found by Lemström (but of feeble intensity) when
the slit of the instrument was directed towards a roof or other object
covered with snow, and even in the snow all round the observer.
[Sidenote: Lemström’s conclusions.]
M. Lemström concluded that an electric discharge of an auroral nature,
which could only be detected by means of the spectroscope, was taking
place on the surface of the ground all around him, and that, from a
distance, it would appear as a faint display of Aurora.
[It should, however, here be noted that the reflection of an Aurora from
a white or bright surface would give, in a fainter degree, the spectrum
of the Aurora itself; and, apart from the phenomena seen by the eye, the
case fails to be conclusive that an Aurora on the surface of the ground
was examined.]
_Mr. J. R. Capron’s Aurora of October 24th, 1870._
[Sidenote: Mr. J. R. Capron’s Aurora, Oct. 24, 1870. Silver glow in
north. Phosphorescent cloud-streamers. Crimson masses on horizon.
Coloured streamers. Corona formed. Aurora fades away.]
Public-domain text, read in full here on John Shaqi.
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