CHAPTER XXI 

 WEATHER AND CLIMATE 



Weather. The condition of the atmosphere at any 

 given time constitutes the weather. The amount of 

 rain, the atmospheric pressure, the direction and the 

 velocity of the wind, the humidity, the state of the 

 sky, and the temperature are factors which determine 

 the kind of weather. We are well aware of the fact 

 that one of the most prominent characteristics of the 

 weather is its changeableiiess. The variations in tho 

 weather are brought about by the rotation of the 

 earth on its own axis, its inclination 011 its axis, its 

 revolution around the sun, and such changes as result 

 from the passage of storms. 



Climate. When we speak of the climate of any 

 region we say it is cold, hot, temperate, dry, or wet. 

 We are then referring to the average weather condi- 

 tions of that region for a long period of time. In 

 general the weather of any region follows the same 

 course from year to year. Occasionally, however, a 

 winter may be very mild, or there may be an un- 

 usually heavy snow. It is thus necessary to have the 

 average of the weather conditions for a long period 



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