154 Atmospheric Origin of the Aurora, ^c. 



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 respects those rarer portions which reflect no sensible 

 light. 



Those who reflect, that there is a depression of about 1° for 

 every 300 feet of elevation, will find little difficulty in admitting 

 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 / Ursse 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'clock, 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 aeronaut, 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 j and when he touched terra firma, his clothes were frozen 

 stiff."* The crystals may have been minute. The following 

 is from another paper, and may perhaps refer to the same ascen- 

 sion. " In. Mr. Lauriat's last ascension from New York, he as- 

 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 miles acted more powerfully than the earth ? 

 Even at the surface, I have inferred, from many hundred observa- 

 tions, that the magnetic intensity is more affected by the forma- 



* New York Commer. Adver. of August 19, 1836. 



t Middlebury Free Press of Nov. 29, quoting the Boston Herald — date not 

 given. 



