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THE AURORA BOREALIS.

THE Aurora Borealis is a luminous appearance, generally observed in high northern latitudes, and commonly to the north of the observer, whence it has got the name of Northern Lights; it is known also among the vulgar, by the name of "the streamers," or the " merry-dancers." The Aurora Borealis may be divided into two kinds, the tranquil and the varying. The tranquil shines with a mild and steady light, similar to the different stages of moon-light, either as it appears near the time of new moon, or as it gradually inereases when the moon becomes more enlightened; sometimes it is more vivid than the light of the moon when full; and it often preserves, for a considerable time, the form in which it first appeared, with little or no variation. Muschenbroek has paid much attention to this kind of meteor, and has given it several names, according to the form which it as sumes; but as these names are founded only in fancy, and are not necessary to an explication of the theory, we shall omit them. The varied Aurora is more remarkable in its appearance, and occasionally exhibits the most brilliant and rapidly diversified forms. The following are some of its very interesting properties: It is usually of a reddish colour, inclining to yellow, and it frequently sends out corruscations of pale light, which seem to rise from the horizon in pyramidal undulating forms, shooting with great velocity towards the zenith. This kind of meteor, which is less frequent as we go towards the Equator, is almost constant during the long winter nights in the Polar Regions. In the Shetland Isles they afford the inhabitants great relief, amid the gloomy darkness of their long and dreary nights. They commonly appear at twilight, near the horizon, of a dun colour, approaching to yellow, and continue in that state for several hours; they afterwards break into streams of stronger light, spread into columns, then slowly alter into innumerable shapes, and vary their colours from all the yellow tints to an obscure russet;

VOL. XV.

frequently covering the whole atmosphere, exhibiting the most romantic forms and the most beautiful appearance. According to Muschenbroek, in that region of the air which is directly towards the north, or which stretches from the north towards the east or west, there at first appears a cloud in the horizon, which rarely rises to the height of 40 degrees. This cloud is sometimes contiguous to the horizon, sometimes detached from it, in which last case the intermediate sky appears of a bright blue colour. The cloud occupies a portion of the heavens, extending in length to 100 degrees, and sometimes still farther. It is generally white and shining, but sometimes black and thick. Its upper edge is parallel to the horizon, bordered by a long train of light, which rises higher in some places than in others. It appears also bent in the form of a bow, or like the segment of a sphere which has its centre considerably beneath the horizon; and sometimes a large white or luminous band is visible, skirting the upper edge of the black cloud. The dark part of the cloud becomes white and luminous when the Aurora has shone for some time, and after it has sent forth several bright and fiery rays." Then, from the superior edge of the cloud, rays issue in the form of jets, which are sometimes many, sometimes few in number,--sometimes close together, sometimes removed several degrees asunder. These jets diffuse a very brilliant light, as if a luminous or fiery liquor were driven with impetuosity from a syringe. The jet increases in brightness, and has less bulk when it at first issues from the cloud; but it dilates and grows dimmer as it goes farther off. There then arises, from a large opening in the cloud, a luminous train, or column, of which the motion is at first gentle and uniform, and which increases in size as it advances. The dimensions and duration of these columns vary considerably; their light is sometimes white, sometimes reddish, sometimes of a blood colour; and as they advance, their colours

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change, till they form a kind of arch in the heavens. When several of these columns, issuing from different places, encounter each other in the zenith, they intermingle with each other, and form, at their junction, a small thick cloud, which seems, as it were, to kindle, and sends forth a light considerably more brilliant than any of the separate columns. This light changes to green, blue, and purple; and, quitting its original station, it directs itself towards the south, in the form of a small bright cloud. When no more columns are seen to issue, the cloud assumes the appearance of the morning dawn, and insensibly dissipates itself. Sometimes the Aurora is formed and disappears in the course of a few minutes; at other times it continues the whole night; and one that was observed by Muschenbroek in 1734, lasted for ten days and nights successively. The lucid. columns are often so transparent, that stars of the first and second magnitudes are visible through them; these also shine through the white border of the horizontal cloud, and sometimes, though rarely, through the opaque cloud itself. But many parts are so thin, that the smallest stars which are visible to the naked eye may be seen through them. A more beautiful spectacle than what is very frequently presented to us in these meteoric appearances, cannot easily be imagined; the spectacle is often grand and terrific, and is sometimes attended with a hissing, crackling noise, which rushes through the air, and is similar to a display of large fire-works. The hunters who pursue the white and blue foxes, on the confines of the icy sea, are often overtaken by these northern lights, at which times their dogs are so much frightened that they will not move, but crouch upon the ground till the noise has passed by them. Maupertuis observed a remarkable Aurora at Oswer-Zornca, which excited his admiration; an extensive region of the heavens towards the south appeared tinged with so lively a red, that the whole of the constellation Orion seemed to be dyed in blood. This light was for some time fixed, but it was soon in motion, and after having successively

assumed all the tints of violet and blue, it formed a dome, the summit of which was near the zenith in the south-west. Its splendour was so great as not to be affected by the strong light of the moon. He adds, that he only observed two of these red northern lights while he was in Lapland, and thinks that they are of rare occurrence in that country, although the Aurora there assumes a great variety of tints; he moreover observes, that they are considered by the poor ignorant natives as ominous, and the forerunners of calamity.

The accounts of noises attending the Aurora Borealis are sufficiently corroborated; they have been heard by numerous persons, and in various places. They have been heard in Hudson's Bay, in Sweden, Norway, and Lapland. Muschenbroek mentions, that the Greenland whale-fishers assured him that they had frequently heard the noise of the Aurora; but he adds, that no person in Holland ever heard any noise occasioned by them. Mr Cavallo, however, declares, that being in Northampton at the time when the northern lights were remarkably bright, he is confident that he heard a hissing or a whizzing sound. In the Orkney and Shetland Isles they are frequently heard. The writer of this article has been told by more than one gentleman from Orkney, that the noise made by the Aurora is often heard by the natives; and one of them assured him that he had sometimes heard it himself. They have also been heard in Canada. As we might very naturally expect, the Aurora Borealis is by no means confined to the northern hemisphere; for similar appearances, and like noises, have been observed and heard in high southern latitudes. If the existence of the Aurora Australis was at any time doubtful, it was completely ascertained by Captain Cooke in his second voyage round the world. "On February the 17th, in 1773,” says Mr Foster, who accompanied Cooke in the capacity of Naturalist, "in south latitude 58 degrees, a beautiful phenomenon was observed during the preceding night, which appeared again on 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 whiteish 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."

The most complete series of observations on the Aurora that has yet been published, is given by Dr Richardson, in "Franklin's Journey to the Shores of the Polar Sea." We extract the following: "I have never heard any sound that could be unequivocally considered as originating in the Aurora; but the uniform testimony of the natives, both Crees, Copper Indians, and Esquimaux, and of all the older residents in the country, induce me to believe that its motions are sometimes audible. These circumstances are, however, rare, as will appear when I state, that I have now had an opportunity of observing that meteor for upwards of two hundred different nights." The Aurora, of which the following is a description, must have been exceed ingly beautiful: "When the Aurora had exhibited itself in this form for a considerable space of time, the whole mass of light suddenly appear ed in motion, and sweeping round on each side, was gathered together to the southward of the zenith. Immediately after, a large portion of it was seen in the S. E., assuming an exact resemblance to a curtain suspended in a circular form in the air, and hanging perpendicular to the earth's surface. The lower edge of this curtain was very luminous, and had a waving motion; and the illusion was farther heightened by the momentary appearance of perpendicular dark lines, or breaks in the light, in rapid succession round the circle, exactly as the waving of a curtain would cause the dark shades of its folds to move along it. This beautiful curtain of light was about

40 degrees high, of a pale yellowish colour, and sent out, on one side, a process which approached the S. E. by E. point of the horizon, and on the other was connected with a long regular arch, terminated in the N. W. horizon, similarly constructed, and having the same waving motion with the curtain itself. All this time the sky was perfectly clear, except in the southern quarter, which, to the height of 4 or 5 degrees, was occupied by dark clouds, apparently intermediate between stratus and cirrostratus." Several theories have been proposed in order to explain the nature of this meteoric appearance; but none of those which have yet been published are satisfactory. The following account and explanation of the theory, which were communica ted to me by Dr T. S. Traill of Liverpool, are conclusive ;-the theory agrees entirely with the phenomena, and leaves, I think, little more to be desired on this subject: "The extent of the Aurora in the Orkneys I never accurately ascertained, but I have occasionally observed it to cover more than two-thirds of the canopy of heaven. I once saw an Aurora of a uniform blue colour slowly rolling from the northern quarter of a cloudless sky, and extending even beyond the zenith; occasionally its volume expanded so as to involve almost the whole heavens, presenting the magnificent spectacle of a vast dome of lambent flame with a circular aperture in the centre.

"The most usual periods for the occurrence of the Aurora in Orkney are about the end of autumn, and the end of winter; but it occasionally occurs at every season of the year, though it is, in general, most vivid in the absence of moonlight. Some philosophers have mentioned, that they have heard a peculiar kind of noise, like the rushing of air, or the rustling of silk, during the appearance of the Aurora Borealis ; this is a circumstance, the truth of which I am able to confirm by repeated observations. I am quite certain that I have heard this rustling noise, which was once particularly distinct as I stood alone, at midnight, on the top of a lofty tower, when every thing was still around. The real height at which this meteor occurs has never

yet been ascertained. In 1716, 1726,
and 1729, the Aurora Borealis was
observed in every part of Europe;
but we do not know that it was the
very same Aurora which was observ-
ed at distant places, else we could
ascertain its elevation in the sky. At
any rate, the Aurora is a meteor which
must be very high in the atmosphere,
from the distance at which we know
one has been visible. It cannot, how-
ever, be higher than the upper limit
of the atmosphere, which does not
exceed 70 or 80 miles; and it is ex-
tremely probable that no Aurora has
ever been observed at an altitude
greater than 45 miles; and, there-
fore, it follows, that the immense
heights given to this meteor, from
observations made by Mairan, and
others, were obtained from false data.
Mairan (at page 74 Traité Physique
Historique de l'Aurore Boreale) has
determined the height of an Aurora
to be 200 leagues, which is evident
ly false; but we are to consider that
he had a particular object in view-
he had formed the strange notion
that the Aurora, as well as the zodi-
acal lights, are both produced by the
solar atmosphere. The supposition
has, however, been completely re-
futed by Laplace: for this illustri-
ous philosopher has proved, that the
sun's atmosphere cannot extend to
the orbit of Mars, much less then
can it extend itself as far as the
orbit of the earth; and, consequent
ly, it can never be the cause of the
Aurora. It is evident that the Aurora
cannot be above the earth's atmos-
phere, because, as it apparently re-
mains stationary for several hours, it
must partake of the common motion
both of the earth and the atmosphere.
This meteor increases in brilliancy as
we advance towards the north; and,
for nearly half the year, it supplies
the absence of the sun to the shi-
vering tenant of the frigid zone.'
For a long time the northern lights
were supposed to be peculiar to the
northern hemisphere, but the voy
ages of discovery in the southern
ocean, and the increasing intercourse
between the northern and southern
hemispheres, have shown that they
prevail also towards the south pole.
The Aurora Australis has been de-
scribed as paler than the Aurora Bore-
alis; but, in all probability, this arises

from comparing the Aurora Borealis
as it appears in our high northern lati-
tudes, with the appearance of the Au-
rora Australis as it appears in much
lower southern latitudes. Some phi-
losophers have ascribed the Aurora to
the inflammation of hydrogen gas in
the upper regions of the atmosphere.
There is considerable reason to sup-
pose, that while various processes are
going on at the surface of our earth,
and particularly during the action of
evaporation, that some water is de-
composed. If this process really goes
on, it must be allowed that the hy-
drogen thus liberated, being much
lighter than air, would rise to the
top of the atmosphere, and, after
rolling down the inclined planes
formed by its upper surface, would
accumulate near the poles. If the
electric fluid pass through this hy-
drogen, it may set it on fire, and
thus produce the Aurora. This hy-
pothesis is, perhaps, the most plausi-
ble that has yet been advanced, to
account for this extraordinary me-
teor. The successive ignition of the
portions of hydrogen, as they come in
contact with the oxygen of the air,
are supposed to occasion the corrusca-
tions of the Aurora; and the small
quantity of oxygen present in such
rare air accounts for the duration of
the combustion. Granting that this
hypothesis is correct, there should
be a vacuum formed towards the
pole by the condensation of the gases,
and an Aurora in our hemisphere
ought generally to be followed by a
southerly wind. Now, Mr Wynne,
in the Philosophical Transactions of
the Royal Society of London, in-
forms us, that in twenty-three cases
which he observed, an Aurora was,
without exception, followed by a
southerly wind. When the Aurora
was very brilliant, the south wind
came on with considerable force
within twenty-four hours; when
the Aurora was faint, the wind
was longer in coming on, was weaker
also, but continued longer. In the
Orkney and Shetland Isles, where
the Aurora is usually much more
brilliant than I recollect ever to have
seen it in any other part of Britain,
it is usually reckoned to be the fore-
runner of a gale; and I have ob-
served, after a vivid appearance there,
in several instances, that it was soon

followed by a strong gale from the south, or from the south south-west. According to the account given in 'Franklin's Journey to the Shores of the Polar Seas,' it is evident that, at the time of an Aurora, electro-magnetism is produced; for, at the time of the appearance of an Aurora, the motion of the magnetic needle was disturbed; and this circumstance is quite agreeable to the above hypothesis. Franklin says, 'the appear ance of the Aurora, and the disturbance it occasioned on the motion of the needle at Fort Enterprise, were so frequent, that the mean monthly variation must have been deduced from but few observations if they had been rejected.' And again, 'the circumstance of the mean variation being least at midnight there, and at Moose-Deer Island, was evi

dently caused by the frequent disturbance in the motion of the needle which the Aurora occasioned; for on those days when it was not visible, the mean diurnal variation followed the course Mr Hood had observed it to do at Cumberland House, being most easterly at the time of the first observation in the morning, and least between three and four in the afternoon. The change in the diurnal variation in these parts of North America seems to be governed by the same law as in England, as the decrease in easterly variation between the morning and afternoon is, in fact, a motion of the needle to the westward."

For much more interesting infor mation on the same subject, we refer to the volume above quoted, and from which these are extracts.

Woman's Love.

THERE'S wassail in Lord Walter's hall, And smoking beeves and red-wine flowing ;

Merry are the hearts of his kinsmen all, And the dames' dark eyes are gladly glowing;

While, lower ranged, his vassal train

Devoutly quaff the foaming ale, Or with the blade, ne'er drawn in vain,

The sirloin's mighty mass assail:

The harp is sounding proudly too,

While chaunts the minstrel old and
hoary,

From Norman spears how Saxons flew
On Hastings' day of deathless glory.

And yet by friends though girded round,—
Though lovely lips and eyes are near
him,—
Though lands, herds, flocks, and gold a-
bound,

And kinsmen love and foemen fear him,

Lord Walter mute and sadly sits,

As were nor guest nor kinsman near; And as his eye is rais'd by fits,

It wears the hurried glance of fear. Pale lips, and eyes deep sunken, shew Passion hath wrought the work of time; But is it pure and blameless woę,

Or sleepless, dire remorse for crime?
While thus he mused, casting a shade
Of sorrow upon every face,
It chanced a distant bugle bray'd

A note that peal'd through all the place.

Full many a cheek grew pale beneath

That bugle's wild and thrilling sound, For it seem'd the blast of one whom death

Long since in foreign land had found. But Walter started with a shriek"He comes! he comes! the grave hath giv'n

Him forth his guilty prey to seek,

To mark how poorly guilt hath
thriv'n."

Out flew bright blades from many a thigh,
The coming horror to destroy,-
While ladies crept their lovers nigh,-
Jesu! 'tis but a tiny boy!

His locks were of as dark a dye

As ever rob'd the raven's wing; And his eyes shone out like the stars on high,

When forth in gloaming hour they spring.

He tripp'd to where Lord Walter stood, And in a soft and witching tone, Which every angry thought subdued,

Thus the dark-eyed youth went on :"It was a Knight, an English Knight, Bound was he for Paynim fight; And with an hundred in his train, With Norman ROBERT cross'd the main. His brother, young Lord Henry, too, With him his maiden faulcheon drew, And many a feat of fame they shar'd, Many a deed of danger dar'd, Till, at the length, this elder Knight Captive was made in unequal fight.

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