THE AUEORA BOREALIS. 749 



seen, and they were particularly numerous from 19th to 26th of 

 February, then they ceased, to reappear on March 2nd ; at the 

 same time changes were observed in the electricity of the air. 

 The observers were driven to the supposition that the negative 

 electricity, being deprived of the possibility of discharge by means 

 of the Aurora, could not fail to accumulate in the lower layers of 

 the atmosphere, which are comparatively good insulators. 



From March 2 to March 11, the Aurora reappeared: during this 

 time the air was a good conductor or, when it insulated com- 

 paratively well, was positively electrified. From March 11 the 

 Aurora entirely ceased, and then follows a period of comparatively 

 low temperature, with the electricity of the air generally negative, 

 a period which lasted until the season when the light prevented 

 all further observations of the Aurora. 



