Upon one occasion, the Aurora was seen immediately after sunset, whilst
bright' daylight was remaining.
A circumstance to which I attach some importance must not be omitted.
Clouds have been sometimes observed during the day to assume the
forms of the Aurora, and I am inclined to connect with the appearance of
these clouds the deviation of the needle, which was occasionally remarked at
such times.
An Aurora sometimes approached the zenith, without producing any change
in the position of the needle, contrary to the general effect, whilst at other
times a considerable alteration took place, although the beams or arches did
not come near the zenith. The Aurora was frequently seen without producing
any preceptible effect on the needle. At such times its appearance was that
of an arch or an horizontal stream of dense yellowish light, with little or no
intTerhnea ld mistoutirobna.nce in the needle was not always proportionate to the agitation
of the Aurora, but it was always greater when the quick motion and vivid
light were observed to take place in a hazy atmosphere.
In a few instances, the motion of the needle was observed to commence at
the instant a beam darted upwards from the horizon. And its former position
was more quickly or slowly regaining according to circumstances. If an arch
was formed immediately afterwards, having its extremities placed on opposite
sides of the magnetic north and south to the former one, the return of the
needle was more speedy, and it generally went beyond the point from whence
it first started.
When the disturbance of the needle was considerable, it seldom regained
its usual position before three or four, p. m. on the following day.
On February 13, at llh 50 p. m., the needle had a quick vibratory motion
between 343° 50' and 344° 40'. This is the only occasion on which a vibratory
motion was observed.
| The disturbances produced by the Aurora were so great that no accurate
deductions could be made respecting the diurnal variation.
I have not heard the noise ascribed to the Aurora, but the uniform testimony
of the natives and of the residents in this country induced me to believe that
it is occasionally audible. The circumstance, however, must be of rare occurrence,
as is evidenced by our having witnessed the Aurora upwards of two
hundred times without being able to attest the fact. I was almost inclined,
last year, to suppose that unusual agitations of the Aurora were followed by
storms of wind; but the more extended opportunities I enjoyed of observing
it in 1821, at Fort Enterprise, have convinced me that no such inference ought
to have been drawn.
The Pith Ball Electrometer, which was placed in an elevated situation in the
air, never indicated an atmosphere charged with electricity.
Upon a review of the observations made upon the dipping-needle, its variations
appear to be so uncertain in their occurrence, that I cannot confidently
ascribe them to the influence of the Aurora.
Observations were made on the Aurora Borealis, in 1822, at Moose-Deer
Island, lat. 61° 18' 8" N. long. 113° 51' 35" W., variation, 25° .40' 47" E.
Being unwilling, however, to swell the Appendix more than necessary, I shall
not insert the tables, but merely remark, that------
Although the Aurora was frequently seen there, the coruscations were seldom
either brilliant or of the variable kind. They caused but little alteration in
the position of the needle, the greatest deviation observed being ,18, and did
not furnish grounds for any additional inferences to. those which were drawn
from the observations on the Aurora made at Fort Enterprise. The display
of light was generally confined to the northern part of the sky, between the
true N.E. and S.W. points, usually at a low altitude; and the Aurora was
observed extending to the southward on four occasions only. This, as well
as the circumstance of the magnetic^ needle being but slightly affected by
the presence of the Aurora during the winter at that place, appears to me
to be deserving of notice, as affording an indication that the seat of the
phenomenon lies more to the northward; and were I to venture an opinion as
to its probable situation, I should say between the latitudes of 64 and 6o
north, or about the position of Fort Enterprise, because the coruscations were
as often seen there in the southern as in the northern parts of the sky, and I
should consider that latitude the most favourable in this part of the globe for
making good observations on this interesting phenomenon.