THE IMPENETRABLE SEA 



The spinning of the earth on its axis is the primary 

 cause of the complexities in the wind systems. If the earth 

 did not rotate, the heated air rising from the world's 

 equatorial belt would be constantly replaced by cool air 

 flowing towards the belt from the poles, which air would 

 be warmed and uplifted again by the sun's heat, and 

 again replaced by more cool air — thus a steady circula- 

 tion of air would be maintained. But any such ''merry- 

 go-round" circulation of the world's winds is interfered 

 with and made extremely comphcated by the fact that 

 the earth itself is a ''roundabout". 



The air above the equator is carried round with its 

 spinning surface at i,ooo miles an hour — making a com- 

 plete revolution every twenty-four hours — while the air 

 above each of the poles is (theoretically) stationary. 

 Between the equator and the poles the air rotates at 

 varying speeds. The effect of all this can be seen in the 

 trade winds. If the world's vast globe were at rest the 

 winds would blow north and south from the equator, 

 under the influence of the sun's rays. The earth's spin 

 gives the main winds — the trades — a twist to the right in 

 the northern hemisphere and to the left in the southern 

 hemisphere. 



So the winds of the world "go like clockwork" and in 

 fact so much like clockwork that they are like a train of 

 geared wheels, all working together. The simile is fairly 

 accurate, for there are other influences on the working of 

 a clock than the gearing of its wheels ; so it is with the 

 winds. 



There is, for instance, the pendulum-like effect of the 

 alternation of day and night, in its regular modification 

 of the "escapement" of the surface heat of the world's 

 land and sea areas. 



The world's winds rage across both land and water 

 surfaces, so that they are affected by the great contrasts 

 of temperature between the continents and the neigh- 

 bouring oceans, which set up wind systems of their own. 



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