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24 REPORT—1845. - 
the ice are invariably confined at this period of the year to very low altitudes above 
the surface of the earth, so as never to form clouds in the usual acceptation of the 
term; but as the season advances and the temperature increases, the aurora occurs 
less frequently; the vapours become entirely detached from the sea, rise to a greater 
height in the atmosphere, and begin to acquire the ordinary appearance of clouds. 
The aurora is no longer confined to their upper surfaces, but a faint auroral light is 
usually seen to fringe the whole of their circumferences, until the vapours are dissi- 
pated by congelation. The author conceives the alternate opening and closing of the 
ice, by which means different portions of vapours are detached from the surface of 
the sea consecutively, give rise to the appearance of different concentric arches of 
aurora, which are occasionally seen. 
As extreme dryness is the peculiar character of the higher atmosphere consequent 
upon low temperatures (which is a state most favourable for electrical induction), 
he concludes that this portion of the atmosphere acquires an opposite state of elec- 
tricity to that below; and since there are no means, such as exist in more temperate 
latitudes, of effecting the restoration of the electrical equilibrium thus disturbed by 
congelation ; and moreover, since within the tropics the aurora is never seen, and 
thunder and lightning are of almost daily occurrence, the latter phenomenon 
indicates the means which nature employs for the maintenance of the equilibrium 
nearer the equator ; and on the other hand, the aurora points out the mode by which 
the same end is silently effected in the cloudless atmosphere of a polar winter, and 
other places where it occasionally occurs, by the interposition and conducting power 
of the frozen particles that are then and there formed; that as these particles are 
generated in the same -proportion as the electricity is developed, so the means of 
restoring the equilibrium are at all times adequate for the purpose. 
He considers the formation of vertical streamers to arise from the illumination of 
columns of these particles in performing the office of restoring the electrical equili- 
brium between the upper and lower strata of atmosphere ; that their vertical ascen~ 
sion is due to the electrical attraction caused by the strata being in opposite states 
of electricity by induction, and in accordance with this he observed that when the 
streamers were projected from an auroral arch, the fringe of light upon the latter 
usually became extinct, or very much diminished in intensity. That the particles 
are subsequently distributed by the winds in various directions, and give rise by 
their illumination to the different places and appearances which constitute a diffused 
aurora, which is usually terminated by a deposition of the particles when they have 
performed their office. 
He found by repeated trials, which were suggested to him by the late Sir Humphry 
Davy at a committee of the Royal Society held previous to the sailing of the expe- 
dition, that ice is an electrical conductor at very low, as well as at mean tempera~ 
tures. The experiments were made with various electrometers, and the friction 
made with silk, woollen cloth, &c., but without producing the least electrical indi- 
cation, although, from the perfect dryness of the atmosphere at low temperatures, 
the electrometers were extremely sensible of the slightest approach of an excited 
electric. A similar conclusion was obtained by completing, by means of ice, the 
connexion in M. Orsteds galvanic apparatus. Mr. Fisher also observes, that the 
conducting power of the frozen particles floating in the atmosphere defeated every 
attempt to determine the state of the atmospherical electricity, by means of the ap- 
paratus suspended from the royal mast-head of the ship, during the time they were 
frozen up each winter, by reason of their deposition upon the insulating glass rods 
of the copper chain used for the purpose; and he has reason to think, had the in- 
sulation been perfect, some very interesting results would have been obtained. 
Taking this view of the subject, the author considers that there exists an irregular belt 
or zone of congelation, circumscribing the pole of each hemisphere, in different parts 
of which displays of aurora more or less occur, according to the amount of the re- 
quired conditions of low temperatures and humidity; and that those parts of the zones 
which cross the northern Atlantic, or in other words, the winter limits of the frozen 
sea which extend from the American to the northern coast of Europe, will be most 
favourable to the production of the aurora, from the circumstance of there being 
there the greatest supply of humidity. This, he observes, is confirmed by observa- 
tion, and is further corroborated by the fact, that gales of wind from the south, which 
