324 THEORY OF WINDS. 



thermal division of the globe, which, as will be 

 seen hereafter, is the magnetic equator, where 

 the great polar currents from the north and 

 south meet and neutralize each other. They are 

 characterized by a constant succession of irre- 

 gular winds and calms, with storms of thunder, 

 lightning, and rain : they are termed by seamen 

 the swamps, or rainy latitudes; and are ex- 

 tremely sultry, owing to the immense quantities 

 of caloric given out during the condensation of 

 so much aqueous vapour. 



During winter, in the northern hemisphere, 

 the polar latitudes being deprived of the sun's 

 rays, while the tropical parallels are heated, we 

 have a predominance of northerly winds, the 

 dense polar air pressing towards the tropics, to 

 restore the equilibrium ; while the greater ve- 

 locity of the middle and tropical than that of the 

 northern latitudes, causes a deflection of the 

 polar currents to the south-west and west, making 

 north-east and east winds, which almost uni- 

 formly succeed to north winds, and continue 

 blowing until an equilibrium is established be- 

 tween the higher and middle latitudes. In the 

 mean time, under the influence of the solar 

 beams, the land soon becomes more heated than 

 the ocean, even south of it, which causes a south 

 wind until the equilibrium is restored between 

 the sea and land atmosphere. 



During summer, in the United States, south- 



