The Atmosphere 



of greatest mean annual temperature, lies to the north 

 of the actual equator. 



The rotation of the Earth greatly affects the direc- 

 tion of the various air currents, deflecting them from 

 their original courses in accordance with definite laws. 

 The Earth rotates from west to east, and a point on 

 the equator naturally moves towards the east with a 

 greater velocity than a point, say, on the tropic of 

 Cancer. The air in contact with the Earth is carried 

 round with it owing to the friction, but air flowing from 

 a region of lower easterly velocity, such as the tropic 

 of Cancer to one of higher velocity, does not immediately 

 take up the speed of the latter. It gets left behind, 

 and thus an observer midway between the tropic of 

 Cancer and the equator, in the region of north winds, 

 would be carried through the air towards the east. 

 This would give the impression of a wind from the 

 east, which, combined with the wind from the north, 

 would produce a north-east wind. Similarly in the 

 Southern Hemisphere the south winds are transformed 

 into south-east winds. 



These winds covering the belts between the tropical 

 calms and the Doldrums blow constantly in the same 

 direction, and are known as the north-east trade winds 

 and the south-east trade winds. 



For similar reasons the southerly winds to the north 

 of the tropic of Cancer become south-westerly winds, 

 and the region is known as that of the Prevailing South- 

 Westerlys, while the corresponding area in the Southern 

 Hemisphere has winds from the north-west known as 

 the Brave West Winds. 



The region in the immediate neighbourhood of the 



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