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Mists and Fogs. 



The formation of all fogs is owing to a partial 

 condensation of aqueous vapour, caused by the 

 abstraction of caloric from colder bodies often 

 by the mixture of air of different temperatures 

 near the earth's surface. For example, during 

 autumn, the temperature of the Mississippi, 

 Ohio, and other great rivers, is nearly the same 

 during night and day ; while that of the land is 

 greatly reduced at night by radiation, especially 

 towards morning, when it is at the extreme of 

 reduction. Under such circumstances, the in- 

 termixture of the land atmosphere at the tem- 

 perature of 35 or 40 F. with that of the water, 

 which is from 50 to 60, produces a fog or mist. 

 The same effect is produced on the eastern coast 

 of the United States during autumn. The land 

 is cooled down by radiation at night, while the 

 temperature of the ocean and the air over it 

 remains nearly the same. During this state of 

 things, whether the wind blows from the sea or 

 land, a mixture of warm and cold air produces 

 fogs. 



Over the banks of Newfoundland, where the 

 warm air from the gulf stream is intermixed with 

 that of the cold water and icebergs of the north, 

 they prevail throughout the year. Nova Scotia 

 is, proverbially, the region of fogs. The dark 

 and thick fogs of England occur during the 

 latter part of autumn and winter, owing to the 



