THE WINDS 



an encyclopaedia of natural science, was a Roman pro- 

 curator and military leader. William Dampier, who 

 wrote ''A Discourse on Winds" (1699) and made invalu- 

 able contributions to meteorology, was a notorious 

 buccaneer. John Dalton's Meteorological Observations 

 (1793)3 ill which he maintained the electrical origin of 

 the aurorae, was published while he was a schoolmaster. 

 But the status of the meteorologist has undergone radical 

 changes during the last hundred years — the study of 

 wind and weather conditions demands the full-time 

 attention of numerous scientific experts. 



The atmosphere which enfolds our earth is an invisible 

 sea which is constantly in motion. Forever striving to 

 attain a state of absolute rest and tranquillity, it is con- 

 tinually being disturbed and "moved on" by the tor- 

 rential, daily-renewed stream of solar energy which pours 

 upon the earth from the sun. 



It is fortunate for us that no area of the atmosphere, 

 however limited, is absolutely at rest for long, for stag- 

 nant air over our heads and around us would soon 

 become foul and poisonous. So the sun keeps the world's 

 air in constant motion, distributing the moisture that 

 makes life possible; carrying dust (necessary to the 

 formation of rain) up to the cloud regions ; spreading 

 seeds of all kinds ; bearing away the smoke of our cities, 

 and other poisonous exhalations including the breath of 

 man himself; and so (in these and many other ways) 

 purifying the atmosphere and directing it to the advan- 

 tage of living creatures. Although solar energy is the 

 primary cause of wind motion there are many other 

 factors which influence the direction and force of the 

 winds. The atmosphere is held to the earth by gravity, 

 but this does not interfere with the fluidity or elasticity 

 of the air, nor with the effects of any pressures acting at 

 points within it, so that all parts of the atmosphere have 

 perfect freedom in their inter-relationships. If the entire 

 atmosphere were left undisturbed within itself it would 



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