152 Atmospheric Origin of the Aurora, §¥c. 
-as well as others which he has believed to exist, between the au 
rora and a certain class of clouds seen in the day time, do not im- 
ply an usual identity of location. He had stated, that the aurora 
is usually higher than clouds, even than cirrous clouds, which are 
often many miles above other clouds, and many miles above the : 
highest mountains. It by no means follows, that its origin is 
above crystals of the invisible kind. That the latter may be form- 
ing and descending for many hours, and in some instances a day, 
before they attain such a number, magnitude and complexity, as 
to form visible haze, is evident from the phenomena of halos and 
vertical solar and lunar columns in a clear sky.. But these crys- 
tals, in their nascent state, must have had a still earlier and higher 
existence. Should it then be thought surprising, that minute 
crystals, in a region far above halos, should require a day longer 
for their aggregation and descent? =~ 
_ It is not my present purpose to discuss at length the question 
as to the intimate nature of the aurora; but I am of opinion that 
in some region, usually high, a crystallization takes place on the 
evening of an aurora, and that the latter originates in the atmos- 
phere. . In the publication above referred to, I have ventured to 
speak of such a thing as “ sence maghetisiies, and to re- 
gard it as the direct cause of the needle’s and as loca: 
ted in a kind of auroral vapor; although it was the prevalent 
pinion of i eb that the aurora, so far as it was magnetic, - 
“was connected with changes in tellurian magnetism alone, that 
is, the magnetism of the solid earth. The variations of the nee- 
dle were thought to afford evidence of variations in the latter; 
and this view was thought to be corroborated by some simulta- 
neous disturbances of the needle in distant parts of the globe. 
Numerous facts might be cited, in corroboration of the atmosphe- 
ric location. Let one at present suffice. During the brilliant and | 
extensive red aurora of Jan. 25, 1837, I observed at Schenectady, 
N. Y., a variation-of the needle of 14° in eighteen minutes,” a 
24° in two hours, and 23° during the night. “At New Haven, the 
variations Were, at one hour, still more rapid, that is, 45’ in two | 
- minutes; but the whole extent observed was only 1°. About 
thirty miles north of New Haven, no change whatever could be 
eted ; whilst at Annapolis, the needle varied to the astonish- 
in ent of 10° during the night.* Are not these facts wholly 
_ * See this Journal, Vol. xxxir, p. 180. 
ae 
