SOME SPECIFIC DESCRIPTIONS OF AURORÆ, INCLUDING RESULTS OF THE ENGLISH
ARCTIC EXPEDITION, 1875-76.
_Captain Sabine’s Auroræ._
[Sidenote: Captain Sabine’s Auroræ.]
Captain Sabine describes Auroræ seen at Melville Island (Parry’s first
voyage, January 15). Towards the southern horizon an ordinary Aurora
appeared. The luminous arch broke into masses streaming in different
directions, always to the east of the zenith.
[Sidenote: Curvature of arches towards each other.]
The various masses seemed to arrange themselves in two arches, one
passing near the zenith and a second midway between the zenith and the
horizon, both north and south, but curving towards each other. At one
time a part of the arch near the zenith was bent into convolutions like a
snake in motion and undulating rapidly.
_Aurora seen at Sunderland, February 8th, 1817._
(‘Annals of Philosophy,’ vol. ix. p. 250.)
[Sidenote: Aurora seen at Sunderland, Feb. 8, 1817. Formation of corona.]
It began about 7 P.M. during a strong gale from the N.W., with single
bright streamers in the N. and N.W., which covered a large space and
rushed about from place to place with amazing velocity, and had a fine
tremulous motion, illuminating the hemisphere as much as the moon does
eight or nine days from change. About 11 o’clock part of the streamers
appeared as if projected south of the zenith and looked like the pillars
of an immense amphitheatre, presenting a most brilliant spectacle and
seeming to be in a lower region of the atmosphere, and to descend and
ascend in the air for several minutes. (This appears to have been the
formation of a corona.) One streamer passed over Orion, but neither
increased nor diminished its splendour.
_Description of Aurora by Dr. Hayes, 6th January, 1861._
[Sidenote: Dr. Hayes’s Aurora, 6th January, 1861.]
‘Recent Polar Voyages’ contains a narrative of the voyage of Dr. Hayes,
who sailed from Boston on the 6th of July, 1860, and wintered at Port
Foulbe. He witnessed a remarkable display of the Aurora Borealis on the
morning of the 6th January, 1861.
[Sidenote: Development of Aurora.]
The darkness was so profound as to be oppressive. Suddenly, from the rear
of the black cloud which obscured the horizon, flashed a bright ray.
Presently an arch of many colours fixed itself across the sky, and the
Aurora gradually developed.
[Sidenote: Rays changed to glow.]
The space within the arch was filled by the black cloud; but its borders
brightened steadily, though the rays discharged from it were exceeding
capricious, now glaring like a vast conflagration, now beaming like the
glow of a summer morn. More and more intense grew the light, until, from
irregular bursts, it matured into an almost uniform sheet of radiance.
Towards the end of the display its character changed. Lurid fires flung
their awful portents across the sky, before which the stars seemed to
recede and grow pale.
[Sidenote: Mixed colours. Colours change. Tongues of white flame formed.]
The colour of the light was chiefly red; but every tint had its turn,
and sometimes two or three were mingled; blue and yellow streamers shot
across the terrible glare, or, starting side by side from the wide
expanse of the radiant arch, melted into each other, and flung a strange
shade of emerald over the illuminated landscape. Again this green subdues
and overcomes the red; then azure and orange blend in rapid flight,
subtle rays of violet pierce through a broad flash of yellow, and the
combined streams issue in innumerable tongues of white flame, which mount
towards the zenith.
The illustration which accompanies this description in the work is
reproduced on Plate II., and forcibly reminds one of the “curtains” of
the Aurora described in the preceding Chapter by Mons. Lottin.
[Illustration: Plate II.]
_Prof. Lemström’s Aurora of 1st September, 1868._
[Sidenote: Prof. Lemström’s Aurora, 1st September, 1868.]
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.]
The description, from my notes made at the time of this fine display, is
as follows:—“Last evening (October 24) the Aurora Borealis was again most
beautifully seen here (Guildford). At 6 P.M. indications of the coming
display were visible in the shape of a bright silver glow in the north,
which contrasted strongly with the opposite dark horizon. For two hours
this continued, with the addition from time to time of a crimson glow in
the north-east, and of streamers of opaque-white phosphorescent cloud,
shaped like horse-tails (very different from the more common transparent
auroral diverging streams of light), which floated upwards and across
the sky from east and west to the zenith. At about 8 o’clock the display
culminated; and few observers, I should think, ever saw a more lovely
sky-picture. Two patches of intense crimson light about this time massed
themselves on the north-east and north-west horizon, the sky between
having a bright silver glow. The crimson masses became more attenuated
as they mounted upwards; and from them there suddenly ran up bars or
streamers of crimson and gold light, which, as they rose, curved towards
each other in the north, and, ultimately meeting, formed a glorious arch
of coloured light, having at its apex an oval white luminous corona
or cloud of similar character to the phosphorescent clouds previously
described, but brighter. At this time the spectator appeared to be
looking at the one side of a cage composed of glowing red and gold bars,
which extended from the distant parts of the horizon to a point over
his head. Shortly after this the Auroral display gradually faded away,
and at 9 o’clock the sky was of its usual appearance, except that the
ordinary tint seemed to have more of indigo, probably by contrast with
the marvellous colours which had so lately shone upon it.”
[Sidenote: T. F.’s description of same at Torquay. Mr. Gibbs’s report in
London.]
T. F., describing the same Aurora from Torquay, says it showed itself at
sundown, attained its maximum at 8, and lasted until 11. At 8 o’clock
more than half the visible heavens was one sea of colour; the general
ground greenish yellow and pale rose, with extensive shoals of deep rose
in the east and west; while from the north, streaming upwards to and
beyond the zenith, were tongues and brushes of rosy red, so deep that the
sky between looked black. Mr. Gibbs reported that in London, at about 8
o’clock, brilliant crimson rays shot up to the zenith, and the sky seemed
one mass of fire.
A facsimile of my water-colour sketch of this fine discharge is given on
Plate III.
[Illustration: Plate III.]
_Mr. Barker’s (superposed) red and white Auroræ, 9th November (1870?)._
[Sidenote: Mr. Barker’s Auroræ, 9th November (1870?). Red Aurora. White
Aurora.]
On the 9th November (1870?) Mr. Barker saw at New Haven (U. S.) a most
magnificent crimson Aurora. At about a quarter to 6 P.M. it consisted of
a brilliant streamer shooting up from the north-western horizon. This
was continued in a brilliant red, but rather nebulous, mass of light
passing upwards and to the north. Its highest points were from 30° to 40°
in altitude. A white Aurora, consisting of bright streamers, appeared
simultaneously and extended round to the north-east. Prof. Newton
informed Mr. Barker that he had observed an equally brilliant red patch
of auroral light in the north-east five or ten minutes earlier.
[Sidenote: Red seen through white.]
Since the lower end of the red streamers was much lower than that of the
white, it would seem as if the red were seen through the white, the red
being most remote.
[Sidenote: Crimson line not seen in white Aurora.]
Spectroscopic observations of this Aurora were made. The crimson Aurora
lasted less than half an hour, and then disappeared. In the white Aurora,
which remained, the crimson line could not be seen.
[Sidenote: Carl Bock’s vibrating rays.]
It may be here noted that during the Aurora seen by Carl Bock in
Lapland, and painted by him by its own light (described, p. 25), he had
the impression of sets of vibrating rays behind each other, and in the
drawing it looks as if streamers were seen behind an arc.
[Illustration: Plate IV.]
_Mr. J. R. Capron’s Aurora of February 4th, 1872._
[Sidenote: Mr. J. R. Capron’s Aurora, Feb. 4, 1872. Masses of
phosphorescent vapour. Rose tints appeared. Aurora from behind clouds.
Formation of corona. Duration of corona. Streamers from corona. Rain
during Aurora. Wind during night. Phosphorescent clouds preceded the
Aurora in daylight.]
My description of this Aurora as seen at Guildford, and as given at the
time, is as follows:—“Last evening, returning from church a little before
8 P.M., the sky presented a weird and unusual aspect, which at once
struck the eye. A lurid tinge upon the clouds which hung around suggested
the reflection of a distant fire; while scattered among these, torn and
broken masses of vapour, having a white and phosphorescent appearance,
and quickly changing their forms, reminded me of a similar appearance
preceding the great Aurora of 24th October, 1870. Shortly some of these
shining white clouds or vapours partly arranged themselves in columns
from east to west, and at the same time appeared the characteristic
patches of rose-coloured light which are often seen in an auroral
display. About 8 o’clock the clouds had to a certain extent broken away,
and the Aurora shone out from behind heavy banks of vapour, which still
rested on the eastern horizon, the north-west horizon being free from
cloud and glowing brightly with red light. And now, at about 8.15, was
presented a most beautiful phenomenon. While looking upwards, I saw a
corona or stellar-shaped mass of white light form in the clear blue sky
immediately above my head[4], not by small clouds or rays collecting,
but more in the way that a cloud suddenly forms by condensation in the
clear sky on a mountain top, or a crystal shoots in a transparent liquid,
having too, as I thought, an almost traceable nucleus or centre, from
which spear-like rays projected. From this corona in a few seconds shot
forth diverging streamers of golden light, which descended to and mingled
with the rosy patches of the Aurora hanging about the horizon. The spaces
of sky between the streamers were of a deep purple (probably an effect of
contrast). The display of the corona, though lasting a few minutes only,
was equal to, if not excelling in beauty, the grand display of October
1870, before described, in which case, however, a ring or disk of white
light of considerable size took the place of the stellar-shaped corona.
What struck me particularly was the corona developing itself as from a
centre in the clear sky, and the diverging streamers apparently shooting
downwards, whereas in general the streamers are seen to shoot up from the
horizon and converge overhead. The effect may have been an illusion; but,
if so, it was a remarkable one. The general Aurora lasted for some time,
till it was lost in a clouded sky; and, in fact, rain was descending at
one time while the Aurora was quite bright. Strong wind prevailed during
the night[5]. The Aurora was probably very extensive, as the evening,
notwithstanding the clouds, was nearly as bright as moonlight. The
peculiar clouds referred to must have preceded the Aurora in daylight,
as I recollect seeing them at 6.30 as we went to church.”
[Sidenote: Aurora predicted.]
They had even then a peculiarly wild, ragged, and phosphorescent
appearance, and so much resembled some I had seen to accompany the Aurora
of October 1870, that I predicted (as came to pass) a display later in
the evening. A _facsimile_ of my water-colour sketch of this Aurora is
given on Plate IV. fig. 1, while the corona and rays are represented
(with rather too hard an outline) on Plate V. fig. 2.
[Illustration: Plate V.]
_Description of an Aurora seen at Cardiff._
[Sidenote: Aurora seen at Cardiff. Formation of corona.]
An Aurora was seen at Cardiff. A dusky red aspect of the sky towards
the north, and extending itself across the zenith westward, made its
appearance about half-past 5 P.M. The lights reached their greatest
intensity at 6 o’clock, when the sky was suffused with a rich crimson
glow, a broad band of colour reaching from N.E. to W. A corona of deep
hue, having rugged sharply defined edges, stood out prominently in the
zenith, apparently on a parallel plane to the earth, and having its
centre almost immediately over the head of the spectator.
[Sidenote: Radii thrown out from corona.]
From this corona, elliptic in form, and in its broadest diameter about
four times the size of the moon, there were thrown out brilliant silvery
blue radii, extending to the N.E. and W. horizon, and presenting the
appearance of a vast cupola of fire.
[Sidenote: Rain fell when Aurora died out.]
At half-past 6 the lights died completely out, leaving masses of cloud
drifting up from the south, and a shower of rain fell. The corona was
remarked upon as unusual. At Edinburgh the sky was brilliant for several
hours. (The date of this Aurora is uncertain, as the account is from an
undated newspaper cutting. It is supposed to be in February 1872, but
could hardly have been on the 4th, as the Aurora of that date did not
reach its maximum development at Edinburgh till 8 P.M.)
_Mr. J. R. Capron’s Aurora, seen at Guildown, Guildford, February 4th,
1874._
[Sidenote: Silvery brightness in N.E. Light-cloud, which moved from E. to
W. Formation of arc in N. Streamers. Horizontal clouds of misty light.]
About 7 P.M. my attention was drawn to a silvery brightness in the
north-east. Above, and still more to the east, was a bright cloud of
light, which looked dense and misty, and gave one the impression of an
illuminated fog-cloud. The edges were so bright that the adjacent sky,
but for the stars shining in it, might, by contrast, have been taken for
a dark storm-cloud. The light-cloud expanded upwards until its apex
became conical, and then moved rapidly from east, along the northern
horizon, until it reached the due west, where it rested, and formed for
some time a luminous spot in the sky. About the same time a long low arch
of light formed along the northern horizon, having a brighter patch at
each extremity; and these being higher in the sky, the arch and turned-up
ends were in shape like a Tartar bow. This bow was permanent; and later
on a cloud of rose-coloured light formed in the east, looking like the
reflection of a distant fire. From the bow also shot up curved streamers
of silver light towards the zenith, which at one time threatened to form
a corona. This, however, did not happen, and the Aurora gradually faded
away, until, when the moon rose about 8, a silver tinge in the east alone
remained. I should also mention that fleecy horizontal clouds of misty
light floated in the north above the bow across the streamers.
Mr. H. Taylor informed me he saw a similar Aurora some three weeks
before, in which the bright horizontal light and short white streamers
were the main characters. I am not sure that the horizontal light-clouds
were not actual mist-clouds illuminated by reflection of the Aurora;
not so, however, I think, the first-mentioned cloud, which had more the
appearance of the _aura_ in the large end of an illuminated Geissler tube.
[Sidenote: Spectrum of the Aurora described.]
I examined the Aurora with a Browning direct-vision spectroscope, and
found Ångström’s line quite bright, and by the side of it three faint
and misty bands towards the blue end of the spectrum upon a faintly
illuminated ground. I could also see at times a bright line beyond
the bands towards the violet. There was not light enough to take any
measurements of position of the lines.
I made a pencil sketch of this Aurora, at the time when the light-cloud
had moved W. and the arc formed, and of the spectrum. These drawings are
reproduced on Plate VI. figs. 1 and 1_a_.
[Illustration: Plate VI.]
_Mr. Herbert Ingall’s Aurora, July 18th, 1874._
[Sidenote: Mr. Herbert Ingall’s Aurora, July 18, 1874. Haze canopy
formed. Bright bluish flames appeared. Beams and streamers appeared.
Oscillatory motion of rays.]
An Aurora of July 18th, 1874, seen by Mr. Herbert Ingall at Champion
Hill, S.E., was described by him as an extraordinary one. About 11
the sky was clear; at midnight the sky was covered by a sort of haze
canopy, sometimes quite obscuring the stars, and then suddenly fading
away. Mr. Ingall was shortly after remarking the sky in the S.E. and S.
horizon as being more luminous than usual, when his attention was drawn
to a growing brightness in the S.W., and a moment afterwards bright
bluish flames “swept over the S.W. and W. horizon, as if before a high
wind. They were not streamers, but bright blue flames.” They lasted
about a minute and faded; but about two minutes afterwards a glowing
luminosity appeared in the W.S.W., and broke into brilliant beams and
streamers. The extreme rays made an angle of 90° with each other, the
central ray reaching an altitude of 50°. The extreme divergence of the
streamers (indicating their height above the earth’s surface), and
their direction (from W.S.W. to E.N.E.) at right angles to the magnetic
meridian, suggested to Mr. Ingall a disturbance of an abnormal character.
The rays had an oscillatory motion for about fifteen seconds, and then
disappeared, “as if a shutter had suddenly obscured the source of light.”
[Sidenote: Mr. Ingall’s remarks corroborated.]
Mr. Ingall’s remarks were corroborated by an observer in lat. 54° 46´
6″·2 N., long. 6h 12m 19s·75 W. The display, however, was more brilliant,
and the intensity of light at midnight illuminated the whole district
as with an electric light. The rays, too, bore tints differing from one
another; the largest seemed to partake of the nature of the blue sky,
while the smaller ones, running parallel with the horizon, were ever
changing from blue to orange-red.
[Sidenote: Rev. C. Gape saw flashes or streaks of a pale blue colour.]
On June 25 (same year?), between 9 and 10 o’clock, the Rev. Chas. Gape
saw at Rushall Vicarage, Scole, Norfolk, in the E.S.E., very frequent
flashes or streaks of a pale blue colour darting from the earth towards
the heavens like an Aurora. The day had been dull and close, with distant
thunder. In the E.S.E. it was dark, but overhead and everywhere else it
was clear and starry.
_Mr. J. R. Capron’s White Aurora of September 11th, 1874._
[Sidenote: Mr. J. R. Capron’s white Aurora of Sept. 11, 1874.]
On September 11, 1874, we were at Kyle Akin, in the Isle of Skye. The
day had been wet and stormy, but towards evening the wind fell and the
sky became clear. About 10 P.M. my attention was called to a beautiful
Auroral display.
[Sidenote: Double arc of pure white light in the N.]
No crimson or rose tint was to be seen, but a long low-lying arc of the
purest white light was formed in the north, and continued to shine with
more or less brilliancy for some time. The arc appeared to be a double
one, by the presence of a dark band running longitudinally through it.
[Sidenote: White streamers. Auroral bow believed to be near the earth.]
Occasional streamers of equally pure white light ran upwards from
either end of the bow. The moon was only a day old, but the landscape
was lighted up as if by the full moon; and the effect of Kyle Akin
lighthouse, the numerous surrounding islands, and the still sea between
was a true thing of beauty. The display itself formed a great contrast
to the more brilliant but restless forms of Auroræ generally seen. I
particularly noticed a somewhat misty and foggy look about the brilliant
arc, giving it almost a solid appearance. The space of sky between the
horizon and the lower edge of the arc was of a deep indigo colour,
probably the effect of contrast. I had a strong impression that the bow
was near to the earth, and was almost convinced that the eastern end and
some fleecy clouds in which it was involved were between myself and the
peaks of some distant mountains.
I have not seen any other account of this Aurora, of which I was able at
the time to obtain a sketch. This is reproduced on Plate VII. It was a
lovely sight, and wonderfully unlike the cloud-accompanied and crimson
Auroræ which I had seen in the South.
It is noticed in Parry’s ‘Third Voyage’ that the lower edge of the
auroral arch is generally well defined and unbroken, and the sky beneath
it so exactly like a dark cloud (to him often of a brownish colour), that
nothing could convince to the contrary, if the stars, shining through
with undiminished lustre, did not discover the deception.
[Sidenote: No trace of brown colour in segment of sky below the arc.]
I saw no trace of brown colour. The segment below the arch resting on the
horizon was of a deep indigo colour.
[Illustration: Plate VII.]
_Dr. Allnatt’s Aurora, June 9th, 1876._
[Sidenote: Dr. Allnatt’s Aurora, June 9, 1876. Band of auroral light
appeared. Streaks of cirro-stratus divided the Aurora. Want of electric
manifestations attributed to absence of sun-spots.]
Dr. Allnatt, writing to the ‘Times’ from Abergele, North Wales, near
the coast of the Irish Channel, reported an Aurora on the night of the
9th June, 1876. After a cool and gusty day, with a strong N.E. wind
and a disturbed sea, there appeared at 11 P.M. in the N. horizon a
broad band of vivid auroral light, homogeneous, motionless, and without
streamers. About midnight a long attenuated streak of black cirro-stratus
stretched parallel with the horizon, and divided the Aurora into nearly
symmetrical sections. On the preceding day the sky was covered with dark
masses of electric cloud of weird and fantastic forms. The season had
been singularly unproductive of high electric manifestations, which Dr.
Allnatt thought might be attributable to the comparative absence of spots
on the solar disk. [It may here be noted how conspicuous the years 1877
and 1878 have been for absence of Sun-spots and of Auroræ.]
[Illustration: Plate VIII.]
_Herr Carl Bock’s Lapland Aurora, 3rd October, 1877._
[Sidenote: Herr Carl Bock’s Lapland Aurora, 3rd Oct. 1877. Lapland Auroræ
generally of the yellow type.]
In January 1878 I had the pleasure to meet, at the Westminster Aquarium,
Herr Carl Bock, the Norwegian naturalist, who accompanied four
Laplanders, two men and two women, with sledges, tents, &c., on their
visit to this country. The Laplanders (as mentioned elsewhere) did not
confirm the accounts of noises said to have been observed by Greenlanders
and others during the Aurora. Carl Bock mentioned to me that the displays
he saw in Lapland were most brilliant, but generally of the yellow type
(the Laplanders called the Aurora “yellow lights”). He saw only one red
Aurora. He kindly lent me a picture (probably in its way unique), an
oil-painting of an Aurora Borealis, entirely sketched by the light of the
Aurora itself.
[Sidenote: A picture painted by light of the Aurora. Movement of the
rays. Inner edge of arc fringed with rays.]
The painting is remarkable for the tender green of the sky, an effect
probably due to a mixture of the ordinary sky colour with the yellow
light of the Aurora. This picture was taken at Porsanger Fjord, in lat.
71° 50´, on 3rd October, 1877. It lasted from 9 P.M. till about 11
P.M. The rays kept continually moving, and certain of them seemed in
perspective and behind the others. It will be noticed that the _inner_
edge of the arc is fringed with rays, contrary to the sharp and definite
margin which is usually presented. Probably two Auroræ or auroral forms
were seen—a quiescent arc in front, and a set of moving streamers beyond.
Two larger and brighter patches of light are seen at each extremity of
the arc, as in the case of the Aurora seen by me at Guildown, February
4th, 1874, which, indeed, the display much resembles. A reduced facsimile
of Herr Bock’s excellent picture is given on Plate VIII.
[Sidenote: Aurora of longitudinal rays.]
Herr Bock also acquainted me that on the following day he saw an
Aurora in which the lines of light, instead of being vertical, were
longitudinal, and were continually swept along in several currents. They
were not so strong as in the former case.
_Rev. T. W. Webb’s Aurora._
[Sidenote: Rev. T. W. Webb’s Aurora. Arc resolved into sets of streamers
moving in opposite directions.]
The Rev. T. W. Webb has described to me in a letter an Aurora very like
that seen by Carl Bock in Lapland, and apparently the prevailing type
in those regions. An arc similar to that figured by Carl Bock appeared
in the N.W., and seemed to resolve itself into two sets of streamers
moving in opposite directions (or the one set might be fixed and the
other moving), like the edges of two great revolving toothed wheels. This
lasted but for a few seconds; but during that interval the tints were
varied and brilliant, including blue and green.
_The English Arctic Expedition 1875-76, under Capt. Sir George Nares._
[Sidenote: English Arctic Expedition, 1875-76. Instructions for use of
officers. Appendix B. Capt. Sir G. Nares’s report. True Auroræ seldom
observed, and displays faint. Citron-line observed on only two displays.
Appendix C.]
In anticipation of the starting of this Expedition, some instructions
for the use of the officers in connexion with the hoped for display of
brilliant Auroræ were prepared:—as to general features of the Auroræ, by
Professor Stokes; as to Polarization, by Dr. William Spottiswoode; and as
to Spectrum work, by Mr. Norman Lockyer and myself. As these instructions
were somewhat elaborate, and will apply to all Auroral displays, I have
supplied a copy of them in Appendix B. They were unfortunately not
brought into requisition, for want of the Auroræ themselves. Capt. Sir
George Nares has reported to the Admiralty, under date 5th December,
1877, as follows:—“Although the auroral glow was observed on several
occasions between 25 October, 1875, and 26 February, 1876, true Auroræ
were seldom observed; and the displays were so faint, and lasted so short
a time, and the spectrum observations led to such poor results, that no
special report has been considered necessary. Although the citron-line
was observed occasionally, on only two displays of the Aurora was it well
defined, and then for so short a time that no measure could be obtained.”
(For Sir George Nares’s further Report see Appendix C, containing
extracts from blue-book, ‘Results derived from the Arctic Expedition,
1875-6.’)
_Aurora Australis._
[Sidenote: Aurora Australis. Mr. Forster’s description. Long columns of
white light spreading over the whole sky.]
In an article on Auroræ in high Southern latitudes (Phil. Trans. No.
461, and vol. liv. No. 53), we find that Mr. Forster, who as naturalist
accompanied Capt. Cook on his second voyage round the world, says:—“On
February 17th, 1773, in south latitude 58°, a beautiful phenomenon was
observed during the preceding night, which appeared again this, and
several following nights. It consisted of long columns of a clear white
light shooting up from the horizon to the eastward almost to the zenith,
and gradually spreading over the whole southern part of the sky. These
columns were sometimes bent sideways at their upper extremities; and
though in most respects similar to the northern lights of our hemisphere,
yet differed from them in being always of a whitish colour, whereas ours
assume various tints, especially those of a fiery and purple hue. The sky
was generally clear when they appeared, and the air sharp and cold, the
thermometer standing at the freezing point.” This account agrees very
closely in particulars with Capt. Maclear’s notice of Aurora Australis
[after referred to], and especially in the marked absence of red Auroræ.
The height of the barometer does not appear to be mentioned, the
temperature being apparently much the same as in the more recent cases.
[Sidenote: Capt. Maclear’s Aurora Australis, 3rd March, 1874. Light of
pale yellow tint only.]
In a letter dated from H.M.S. ‘Challenger,’ North Atlantic, April 10th,
1876, Capt. Maclear was good enough to communicate to me some particulars
of an Aurora Australis seen 3rd March 1874, in lat. 54° S., long. 108° E.
The letter is mainly descriptive of the spectrum (which will be described
in connexion with the general question of the spectrum of the Aurora).
It states that the red line was looked for in vain, and that the light
appeared of a _pale yellow_, and had none of the rosy tint seen in the
northern displays.
[Sidenote: Capt. Maclear’s Auroræ described in ‘Nature.’]
Capt. Maclear has since contributed to ‘Nature,’ of 1st November 1877, a
description of four Auroræ seen from the ‘Challenger’ in high southern
latitudes (including the one communicated to me). He speaks of the
opportunity of observing as not frequent, either from the rarity of
the phenomena, or because the dense masses of cloud prevalent in those
regions prevented their being seen except when exceptionally bright.
There were four appearances described:—
[Sidenote: Feb. 9, 1874.]
(1.) At 1.30 on the morning of February 9th, 1874, preceded by a watery
sunset, lat. 57° S. and long. 75° E., bar. 29·0 in., ther. 35°; brilliant
streaks to the westward. Day broke afterwards with high cirrus clouds and
clear horizon.
[Sidenote: Feb. 21, 1874.]
(2.) At 9.30 P.M., February 21, 1874, lat. 64° S., long. 89° E., bar.
28·8 in., ther. 31°; one bright curved streamer. The Aurora preceded a
fine morning with cumulo-stratus clouds, extending from Jupiter (which
appeared to be near the focus) through Orion and almost as far beyond.
Under this a black cloud, with stars visible through it. Real cumuli
hid great part of the remainder of the sky, but there were two vertical
flashing rays which moved slowly to the right (west). Generally the
Aurora was still bright.
[Sidenote: March 3, 1874. Auroral line found in light to southward.]
(3.) At midnight, March 3rd, 1874, lat. 53° 30´ S., long. 109° E., bar.
29·1, ther. 36°, after some days’ stormy weather, a brilliant sunset,
followed by a fine morning. Soon after 8 P.M. the sky began to clear
and the moon shone out. Noticing the light to the southward to be
particularly bright, Capt. Maclear applied the spectroscope, and found
the distinguishing auroral line.
[Sidenote: Brilliant white clouds seen.]
About midnight the sky was almost clear, but south were two or three
brilliant light clouds, colour very white-yellow, shape cumulo-stratus.
From about west to near south extended a long feathery light of the same
colour, parallel with the horizon, and between south and west there
appeared occasionally brilliant small clouds. The upper edges seemed
hairy, and gave one the idea of a bright light behind a cloud. The forms
changed, but no particular order was noticed.
(Here follows a description of the spectrum, and the mode in which a
delineation by the lines was obtained.)
[Sidenote: March 6, 1874. Capt. Maclear suggests whether a low barometer
has to do with the absence of red.]
(4.) At 8 P.M., March 6th, 1874. This was a slight Aurora, seen to the
southward; after this the clouds changed to high cirrus. Capt. Maclear
suggests whether a low barometer has any thing to do with the absence
of red in the spectrum, the normal state of the barometer being an inch
lower in those regions than in more temperate latitudes.
[Sidenote: Barometer falls after the Aurora, and strong gale from the S.
or S.W. follows.]
Edin. Encyc. vol. iii. article “Aurora.” Dr. Kirwan observed that the
barometer commonly falls after the Aurora. Mr. Winn, in the seventy-third
volume of the Phil. Trans., makes the same remark, and says that in
twenty-three instances, without fail, a strong gale from the south or
south-west followed the appearance of an Aurora. If the Aurora were
bright, the gale came on within twenty-four hours, but was of no long
continuance; if the light was faint and dull, the gale was less violent,
longer in coming, and longer in duration.
[Sidenote: Pale yellow glow rare in the Aurora Borealis.]
The pale yellow-coloured glow referred to by Capt. Maclear is, in my
experience, rare in the Aurora Borealis. It is probably the “æqualiter et
sine eruptionibus aut radiis _fulvi_,” described by Seneca (_antè_, p.
1), and may probably belong to more southern climes.
[Sidenote: Spectrum of Auroræ Australes extends more into the violet.]
We shall see too, by-and-by, that these Auroræ Australes as to spectrum
extend more into the violet than the Aurora Borealis. The yellow, as
complementary to violet, is likely thus to make (in the absence of the
red) its appearance.
It is, however, somewhat singular that Carl Bock found almost exclusively
yellow Auroræ in Lapland.
In Proctor’s ‘Borderland of Science,’ article “The Antarctic Regions,”
we find quoted a passage from a letter by Capt. Howes, of the ‘Southern
Cross,’ in which a graphic description is given of a Southern Aurora:—
[Sidenote: Capt. Howes’s description of a Southern Aurora.]
“At about half-past one on the 2nd of last September the rare phenomenon
of the Aurora Australis manifested itself in a most magnificent manner.
Our ship was off Cape Horn, in a violent gale, plunging furiously into
a heavy sea, flooding her decks, and sometimes burying her whole bows
beneath the waves. The heavens were as black as death, not a star was to
be seen, when the brilliant spectacle first appeared.
[Sidenote: Balls of electric fire resting on mast-heads &c.]
“I cannot describe the awful grandeur of the scene; the heavens gradually
changed from murky blackness till they became like vivid fire, reflecting
a lurid glowing brilliancy over every thing. The ocean appeared like
a sea of vermilion lashed into fury by the storm, the waves dashing
furiously over our side, ever and anon rushed to leeward in crimson
torrents. Our whole ship—sails, spars, and all—seemed to partake of
the same ruddy hues. They were as if lighted up by some terrible
conflagration. Taking all together—the howling, shrieking storm, the
noble ship plunging fearlessly beneath the crimson-crested ways, the
furious squalls of hail, snow, and sleet, drifting over the vessel, and
falling to leeward in ruddy showers, the mysterious balls of electric
fire resting on our mast-heads, yard-arms, &c., and, above all, the awful
sublimity of the heavens, through which coruscations of auroral light
would shoot in spiral streaks, and with meteoric brilliancy,—there was
presented a scene of grandeur surpassing the wildest dreams of fancy.”
The foregoing picture presents a singular contrast to the yellow-white
Auroræ described as seen in high southern latitudes by Capt. Maclear,
and is interesting as a southern Aurora of a red or ruddy tint. Looking,
however, at the extreme rarity of red Auroræ in those latitudes, and
the description of “mysterious balls of electric fire resting on our
mast-heads, yard-arms, &c.” (a phenomenon not often noticed in connexion
with the Aurora), it suggests itself that the case in question may have
been an instance not of a true Aurora, but of an electric display, with
conditions approaching those experienced by travellers who have found
themselves in mountainous districts surrounded by storm-clouds charged
with electricity[6].
_Prof. Piazzi Smyth’s Typical Auroræ._
[Sidenote: Prof. Piazzi Smyth’s typical Auroræ.]
Prof. Piazzi Smyth was kind enough lately to send me the fourteenth
volume of the ‘Astronomical Observations made at the Royal Observatory,
Edinburgh, during the years 1870-1877.’ This volume, amongst its other
interesting matter, affords some valuable information on the subject
of the Aurora Borealis. The Aurora plates are five in number, three
comprising some well-executed chromo-lithographs of typical Auroræ, from
sketches made by Prof. Smyth, the other two plates being of the Aurora
spectrum. The Auroræ delineated are thus described:—
[Sidenote: Aug. 6, 1871, quiescent arc. August 21, 1871, active arc.]
Plate 5. (August 6, 1871.) An example of a mild quiescent kind of auroral
arc, with dark cavernous substratum. (August 21, 1871.) An example of a
bright large active arc darting out rays.
[Sidenote: Sept. 7, 1871, arc streamers and clouds. May 8, 1871, double
arc (longitudinal).]
Plate 6. (September 7, 1871.) An auroral arc, with streamers and dark
clouds, and maintaining a bright appearance though in proximity to
the moon. (May 8, 1871.) A double-arched auroral arc (the arches are
longitudinally arranged).
[Sidenote: April 28, 1871, multiple arc. Oct. 25, 1870, coloured Aurora.]
Plate 7. (April 28, 1871.) A multiple-arched arc of Aurora with
moonlight. (October 25, 1870.) A case of grandest coloured Auroræ, or
Aurora superb and almost universal.
All the foregoing drawings are very vivid and striking, and form a most
interesting set of typical forms of Auroræ.
According to my own experience, the Aurora with arches arranged
longitudinally, thus, [Illustration], is the rarest of all the forms. I
have not met with it myself, nor do I recollect an illustration of one
other than Prof. Smyth’s.