* 
154 Atmospheric Origin of the Aurora, §e. 
many times as high as ordinary clouds. Physical considerations 
have induced me to refer its origin’ to the earth’s atmosphere. 
The height of this is well known never to have been determined, 
so far as —~ evens rarer portions which — no > senile 
light. 
“Those oaks eeldct that there is a depression of obvi 1° for 
every 300 feet of ‘elevation, will find little difficulty in. adraitting 
the existence of crystals of snow above us in summer.’ The fol- 
lowing facts have a bearing on this, as well as on the connection 
between the aurora, snow, and magnetism. “On the 16th of Au- 
gust, 1836, I observed, at Schenectady, an aurora, at 10 P. M., 
chiefly obscured by clouds, and a faint aurora with three or four 
short streamers extending to the height of 7 Urse Majoris, at 2h. 
10m. next morning. The sky was clear, and remarkably so du- 
ring the forenoon, At 7 A. M., the magnetic intensity was high 
and remarkably variable ; the time required for 100 oscillations of 
a suspended needle being: 270 seconds at 7 o’elock,. and 280 ten 
minutes later.. Rain commenced at 9 P. M.-of the 18th, about 
two days after the first appearance. Quantity during the night, 
.32 inch. On this day, the 18th, an aéronaut, Mr. Lauriat, who 
ascended, from New York over Long Island, encountered what 
was called by the papers “a pretty severe snow storm in the upper 
regions ; and when he touched terra firma, his clothes were frozen 
stif’* "The crystals may have been minute. The following 
cended about five miles, and proceeded over a hundred miles. 
He passed through clouds of sleet, which covered his balloon 
with icy particles. But what was more interesting, he discovered. 
that when he was at the greatest altitude, the needle of a com- 
pass which he had with him did not have the least tendency to 
exhibit polar attraction, but wavered about at all points of the 
compass.” May we not conclude, that the atmospheric magnets 
at the height of five milés acted more powerfully than the earth ? 
Even at the surface, I have inferred, from many hundred observa- 
Sais: be the magnetic intensity: is more affected by the forma- 
is ork Commer. Adver: achaiie 19, 1836. « 
Er Fies Prestof Moy. %, =) ning te Boo ltt mt 
