I think I have on some occasions discerned a polarity in the massés of
cloud belonging to a certain kind of cirro-stratus, which approaches to cirrus,
by which their long diameters, having all the same direction, were made to
cross the magnetic meridian nearly at right angles. The apparent convergence
of such masses of cloud towards opposite points of the horizon, which
has been frequently noticed by meteorologists, is of course an optical deception,
produced when they lie in a plane parallel to that on which the observer
stands. These circumstances are here noticed, because if it should be hereafter
proved that the Aurora depends upon the existence of certain clouds, its
apparent polarity may, perhaps with more propriety, be ascribed to the. clouds
themselves which emit the light ; or, in other words, the clouds may assume
their peculiar arrangement through the operation of one cause, (magnetism for
instance,) while the emission of light may be produced by another, a change
in their internal constitution perhaps, connected with a motion of the electrical
fluid. These crude opinions are offered with diffidence, and my knowledge
on these subjects is so limited, that I attach no importance to them ; but it
appears to me that they would be strengthened, were the attempts now making
to excite magnetism by the electrical or galvanic fluid, to prove successful.
Generally speaking, the Aurora appeared in small detached masses for some
time before it assumed that convergency towards opposite parts of the horizon,
which produced the arched form. An observation that I would connect with
the previous remarks, by saying that it was necessary for the electric fluid (or the
Aurora, if they are the same) to operate for some time before the polarity, of
the thin clouds in which it has its seat, is produced. This part of the subject,
however, is more intimately connected with the interesting observations made
on the variation' of the magnetic needle by Captain Franklin and Mr. Hood.
The object of my notes was merely to record the optical appearances of the
meteor.
An electrometer, constructed upon Saussure’s plan, placed in an elevated
situation out of doors, exhibited no signs of a change from the atmosphere at any
time during the winter. The electricity of our bodies, however, at times was so
great, that the pith balls instantly separated to their full extent upon approaching
the hand to the instrument, and our skins were in the middle of winter so
dry, that rubbing the hands together considerably increased their electricity,
and at the same time produced a smell similar to that which is often perceived
when the cushion of an electrifying machine rubs hard against the cylinder.
The same thing was observed more sensibly in some stuffed quadrupeds that
hung in our apartments. Their furred skins, whether rubbed or not, often
accumulated such a charge of the electrical fluid, that when the knuckles were
presented to them, they gave a smart shock which was felt as far as the
elbow.
The Aurora did not often appear immediately after sunset. It seemed
that the absence of that luminary,, for some hours, was in general required for
the production of a state of atmosphere favourable to the generation of the
Aurora. On one occasion) only. (March 8th) did I observe it distinctly, previous
to the disappearance of day-light.
By the way of more perfectly describing one form of the Aurora, rather
than with the view of drawing any inference, I shall state that the slender
beams of light which compose the Aurora when its motions are rapid, are exactly
similar to what would, be produced by a quick succession of electric
sparks, elicited from a charged cylinder, by a body studded with a row of points,
moved rapidly to and fro before it.—Or, supposing a long range of cloud, were
to commence at one end, to impart, from successive points of its surface, its
charge to a similar parallel mass, a current of light would be produced,, apparently
consisting of parallel-beams, lying at right angles to its line of direction,
as described on the night of the 29-30th December, at 2h. a.m. Were the clouds
supposed to lie in- different planes, and to be bounded by curved edges, every
variety of form which that species of Aurora assumes might be produced. The
colour of the flight of the Aurora is not always noted in the following pages, but
when faint it was generally steel-gray, or that of the galaxy. When the low
hazy modification of cirrcr-stratus appeared in the sky, the light, for the most
part, was a gold-yellow colour, moreor less deep; and when the sky was clear,
or when only a few fine threads or thin shoots of cloud were visible, the colours
were vivid and prismatic.
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 instances
are, however, rare, as will appear when I state that I have now had an