INDIAN SUMMER. 361 



to the point of saturation by aqueous vapour, 

 than that of a large continent and, therefore, 

 that the same, or even a less reduction of tem- 

 perature must occasion denser fogs and darker 

 days in Great Britain and other insular coun- 

 tries of the higher latitudes, than in continental 

 regions. 



The Indian summer of the United States is 

 closed by the commencement and predominance 

 of northerly winds, which condense the aqueous 

 vapour that has been borne from the ocean by 

 southern breezes, causing dark cloudy weather, 

 and general rains or snows, according to the 

 latitude and elevation ; after which, the reign of 

 winter is established and the air becomes dry, 

 clear, and cold, except in the neighbourhood of 

 the lakes, or of the ocean, where it partakes of 

 an insular character. 



Aurora Borealis. 



Before concluding this general and imperfect 

 survey of the agency of caloric in meteorological 

 phenomena, it may not be improper to notice 

 the leading facts connected with the aurora bo- 

 realis and australis, or the northern lights, as 

 they are commonly called on this side of the 

 equator. 



It has been already shewn, that the atmosphere 



