THE ENGINE OF THE AIR 



ONE cannot talk of the Ocean River as a great circulating 

 system storing and releasing tropical heat throughout 

 the North Atlantic without describing the partner and indeed 

 the motivating force of the currents of the sea — the similar 

 vast, circulating current of air that acts like an immense fly- 

 wheel powering the Atlantic gyre. Sir Napier Shaw, in a sim- 

 plification of the North Atlantic weather system, describes 

 the climate as a kind of steam or water-vapor engine, heated 

 by the sun, with the tropic seas as the boiler room and the 

 walls of pressure as the containing boiler. The water vapor of 

 the air, in its ability to pick up and release heat in the piston 

 thrust of the wind, acts as the steam in a world-wide steam 

 engine. In a word, the carriage of heat and its release as wind 

 energy is the powerhouse of the world we live in. 



Now if this were a strictly scientific treatise, an exact ac- 

 counting of the variations in the radiation of the sun, in tem- 

 peratures, in water-vapor pressures, and in wind velocities, 

 under all kinds of conditions, could be expressed in compli- 

 cated mathematical formulae. Instead, we shall keep to every- 

 day terms. Where heat is available at the sea surface it gives 

 energy to the evaporation of water into the air. When air 

 is forced aloft, water drops out and heat energy is released. 

 This is convection or the transference of heat. There is 



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