ATMOSPHEROLQGY. — FOG. 445 



the surface, there is scarcely a chance of a greater 

 error than 8 miles ; whereas, in an observation taken 

 upon deck, there is an equal chance of a mistake of 

 near a degree. 



This method of observing the sun's altitude, is 

 equally useful when the horizon is intercepted by 

 land, as when it is obscured by a fog. 



Fogs are more common near the ice, than in the 

 vicinity of land ; more frequent in open seasons than 

 in close seasons ; and more intense and more com- 

 mon in the southern fishing stations, than in the 

 most northern. 



