zenith, to carry on the similitude, the folds of the curtain proceeded in several
beautiM festoons towards the-north and south, and had occasionally
a slow motion, as if it were folding and unfolding again and again. The
moon at this time shone with a bright light, and illuminated several layers
of cloud (cirro-stratus) in the N.E., every other part of the sky being unclouded.
At 2h. a. m. a large homogeneous sheet of rare light was spread over
20 degrees on each side of the zenith, and near the horizon there were many
layers of cirro-stratus, some of them pretty dense, ■so: as to obscure the
moon when they passed over its face. The rapid was quite, inaudible at
this time.
December 27th, 1820.
Hour. Temp. Wind.
9 -4 2 • Calm. Slight fog, rapid: very loud.
10 -4 3 do. do.
Noon —40 N.E. Light., Zenith cloudless—light greyish blue—stratus
creeping along the valleys—fine day.
9 -4 5 N.E. Light. Clear.
11 do. Rapid, very loud.
Midnt. — 45
At llh. p.m., the sky clear, the moon not yet risen, but many stars visible,
A beam of light, about 8° broad, rose from 10° above the horizon in the
S.E.b.S., and gradually becoming fainter upwards, disappeared a little south
of the zenith. After continuing stationary for some time, it sent forth a beam
of light from its south-east end, which extended 11° more to the northward,
whilst its fainter end was at the same instant prolonged, so. as to form a complete
arch, terminating in the N.W.b. W. horizon. A little haze was visible
at this time in the southern horizon.
At midnight the Aurora formed a somewhat interrupted circle round the sky,
about 15° high, which sent down from its N.W.b. W. and.S.E. points, several
pointed processes which nearly touched the horizon. Some large, flexuose
streaks, and masses of light traversing the zenith, connected the northern with
the southern part of the circle; and there were also a few detached irregular
masses of light in other parts of the sky. The best defined part of the circle
was in the N.E. quarter, and here a quick lateral motion to and fro was produced,
as if by its separation into perpendicular bars. It was aboüt 8° broad
at this place. During the continuance of this phenomenon, many beams of
light rose perpendicularly from the upper margin of the circle, but before they
reached the zenith, their extremities were bent from their course so as to make
various curves side-ways, or even to appear as if rolled up upon themselves.
When the Aurora had exhibited itself in this form for a considerable space
of time, the whole mass of light suddenly appeared in motion, and sweeping
round on each side, was gathered together to the southward of the zenith.
Immediately thereafter 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 perpendicularly 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° high, of a pale-yellowish, colour, and
sent forth on the one side a process which approached the S.E.b.E. point of
the horizon, and on the other was connected with a long regular arch, terminating
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° was occupied by
dark clouds, apparently intermediate between stratus and cirro-stratus.
Half an hour after its first appearance, this curtain-formed Aurora was resolved
into a nUmber of detached irregular portions, which sometimes increased
rapidly in every direction until they met with other masses, either before existing
or appearing at the instant, and formed an uniform sheet of light which
covered the whole sky. The formation of this great sheet of light was so rapid,
that the eye could only trace'its progress partially, and its,dissolution and reappearance
were equally sudden.
At 2h. p.m., the moon arose. A clear sky. The Aurora fainter and farther
to the southward than before.