809 
Progress of the Aurora Borealis. 
formed. A detachment into separate groups sometimes takes 
place immediately previous to the disappearance of the meteor ; 
but sometimes, also, it is not immediately followed by that dis- 
appearance, but the zone becomes again complete, or nearly so, 
at a farther stage of its progress southward. 
But no anomalies have at any time^ been observed : nothing 
that is inconsistent with the described order of the phenomena. 
Thus, in whatever part of the heavens the pencils of rays have 
made their appearance, they have never been seen not directed 
to the zenith, or a point a little southward of it ; the zones of 
light have never been seen moving northward, or quite station- 
ary ; comparatively short pencils of rays may be mingled occa- 
sionally with long ones, at or under 45° elevation, on account of 
their frequently breaking short, but no long pencils of rays have 
been observed near the zenith ; and at the zenith no parallel 
rays have at any time been seen, but only the narrow belt of 
nebulous light. 
It is quite evident, that the only conditions that can explain 
and reconcile all these appearances, are, that the pencils of rays 
of the aurora borealis are vertical, or nearly so, and form a deep 
fringe, which stretches a great way from east to west, at right 
angles to the magnetic meridian, but which is of no great thick- 
ness from north to south ; and that the fringe moves southward, 
preserving its direction at right angles to the magnetic meri- 
dian. 
In regard to the velocity with which the meteor moves towards 
the south, that is exceedingly various. It was once seen to pass 
in the space of half an hour from 45° N. of the zenith, where it 
was first observed, to 80° S. of that point, where it became 
extinct. Its light, in that instance, was uncommonly vivid. 
At other times the meteor has been seen to move comparatively 
so slowly, that its motion could only be discovered by an obser- 
vation continued for some considerable time. Its light in these 
cases was faint ; so that the intensity of the light appears con- 
nected with the rapidity of the progress southward. 
The meteor occurs when the atmosphere is quite clear, as 
well as when it is partially obscured by clouds ; and, even when 
a compact fleece of clouds covers the whole heavens, its exist- 
ence in the higher regions is frequently ascertained by the re- 
