CHAPTER IV 

 THE WEATHER 



28. General statement. The winds and the weather are 

 perpetually interesting in connection with our study of the 

 air. The wind changes so frequently and apparently so aim- 

 lessly that it has become a symbol of fickleness, and we say 

 of a changeable person that he is as " changeable as the wind." 

 The rains come and go in an irregular way that makes it very 

 difficult for us to feel any confidence in our plans if they are 

 subject to disturbance by the weather. Weather signs are 

 numerous. Many of these are the result of the experience of 

 many years and frequently come true, while others are only 

 the crudest superstition. In either case the people who believe 

 in them cannot explain why things should happen as the 

 sign indicates, so the matter is as great a mystery as ever 

 to many persons. 



We have rain when there is a cause for rain, and the wind 

 blows this way or that when the appropriate causes are at 

 work. If we are able to discover and understand the causes 

 of all things connected with the weather, it will no longer be 

 mysterious, and probably we shall be able to foretell it with 

 certainty. Men have not yet been able to discover all the 

 causes which are at work in the production of our weather, 

 but enough have been discovered to make the weather much 

 less mysterious. In this chapter an account will be given of 

 some of the most important facts that are known at present. 



29. Air pressure and winds. The first thing we must find 

 out about is the winds, for most other features of the weather 

 depend upon winds. Winds are merely air in motion, and of 

 course the faster the motion the harder the wind is said to blow. 



28 



