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Atmospheric Origin of the Aurora, §*c. 149 
The following is a summary. .- 
‘That crystals of snow more minute and a 
which occasion halos, and usually too minute to produce sensible 
opacity, are always present in the atmosphere, above the region - 
of ordinary clouds, during the time of this meteor, we are indu- 
ced to believe from a comparison of the results of the foregoing 
observations. Several of these results are believed to be. new. 
The following are some of the circumstances which have a bear- 
ing upon this question. 
“Ist. Those seasons of the year and -those hours of the yight 
when it most frequently occurs, are favorable both to the iin 
and congelation of aqueous vapor in the atmosphere. — - 
2d. The clearness of the sky, which at such times is usually 
either general or total. 
3d. The usual northerly breeze at the earth’s surface, and the 
northeasterly breeze in the high region of the meteor. 
Ath. The usual depression of the temperature, at those heights 
at which thermometrical observations are made. 
5th. The clouds which usually succeed the meteor immediately 
or on the same evening, and which often present the appearance 
of being continuous and identical with the auroral matter. 
6th. The snow that in-weather sufficiently cold, almost uni- 
versally follows the meteor, after such an interval as the sim- 
ple -erystals might be expected to require for aggregation in more 
plicated groups and descent to the earth’s surface. 
th. The rain that almost universally succeeds it, after about 
= same interval, whenever the temperature of the lower atmos- 
slecic strata is motlicieas to melt falling snow. 
8th. The co-existence of halos with regular crystals, the con-_ 
nexion between halos and auroral clouds, and between auroral 
clouds and vertical lunar columns, sag the anslosy between au- 
roral clouds and the aurora borealis. 
9th. The pinnate appearance of composite auroral clouds, — 
appear (so to speak) like large crystals.’ 
From this point, the author, not finding any former theory : 
the aurora not liable to great. objections, has ventured into the 
— of speculation, and in relation to the intimate nature of 
the phenomenon, and under the 4th head, of views-of a more 
hypothetic class, has ventured to inquire whether atmospheric 
erystallizations may not occasion the development of auroral 
