METEOROLOGICAL OBSERVATIONS. 
725 
estiiblisl'.ed, by wliich tliis subtle fluid might be propagated to short distances; but the greater 
dryness of the air, both aljove and below this region of thin mist, would oppose an uncon- 
ducting barrier to its escape. As soon as one thin cloud, a thin stripe of cirrus, or fleecy 
portion of cirro-stratus or cirro-cumulus, became charged with electricity, it would occasion, 
by the laws of electric phenomena, an ojrposite electrical state in that portion nearest it; and 
these opposite electricities would instantly attract each other, fly together, burst forth in fire, 
and become neutralized. If there should be a plane in which such thin clouds are formed, 
the subversion and re-establishment of the balance of electricity being thus begun would be 
rapidly propagated throughout the whole of this space, and produce that rapid, undulatory 
motion which we observe in the Aurora Borealis.” 
In considering the subject of the Aurora Borealis, my attention was drawn to a fact 
which does not appear to me to have been hitherto noticed. I allude to the direction in 
which the Aurora generally makes its first appearance, or, which is the same thing, the quarter 
in which the arch formed by this meteor is usually seen. It is remarkable, that in this country 
the Aurora has always been seen to the northward ; by the expeditions which have wintered 
in the ice it was almost always seen to the southward ; and by the Blossom, in Kotzebue Sound, 
S.'jO miles to the southward of the ice, it was, as in England, always observed in a northern 
direction. Coupling this with the relative positions of the margins of the packed ice, and with 
the fact of the Aurora appearing more brilliantly to vessels passing near the situation of that 
body, than by others entered far within it, as would seem to be the case from the reports of the 
Greenland ships, and from my own observations at Melville Island and at Kotzebue Sound, 
it does appear, at first sight, that that region is most favourable to the production of the meteor. 
I do not, however, presume to offer any hypothesis on the subject ; but having witnessed the 
extraordinary change that takes place in the atmosphere, along the whole line of ice covering 
the Polar Sea, I should be remiss if I omitted to direct the attention of the natural philosopher 
to the circumstance. There is perhaps no part of the globe where the atmosphere undergoes 
a greater or more sudden change than over this line of the ice. A diminution of 10° or 15® 
of temperature constantly occurs within the space of a few miles : the humid atmosphere over 
the ocean may sometimes be seen laden with heavy clouds, which disperse as they arrive at 
this line of reduced temperature, and leave the region over the ice exposed to a bright 
sunshine. Indeed the extraordinary effect of this large body of ice upon the atmosphere, 
particularly when the sea is deep and the temperature of the ocean and its superstratum 
of air high, as between Spitzbergen and Greenland, will scarcely be credited by persons 
who have not witnessed it. Mr. Scoresby has given some extraordinary instances of this 
in his Arctic Voyages; and to these I will add one of many which fell under my own 
observation. The ships of the first polar expedition were beset in the ice about nine 
miles from the open sea. It was blowing a hard gale upon the ice, and we could perceive 
a ship carrying off' under storm stay-sails only. There was nothing between us and the 
ship to intercept the gale, and yet we were beealmed during the whole of the day. The 
atmosphere over the open sea was loaded with clouds (nimbi), while that over the ice enjoyed 
a bright sunshine throughout. The limits of these opposite states of the atmosphere, by 
seamen called the ice-llin'k, were marked by a well-defined line, nearly perpendicular 
