WEATHER 183 



Weather Changes. We have learned that " weather " 

 is a very inclusive term. It includes all the atmospheric 

 conditions that can be observed, such as temperature, 

 the amount and kind of precipitation, the humidity of the 

 air, the condition of the sky with reference to the clouds, 

 and the direction and velocity of winds. 



In the torrid zone the weather is quite regular. In the 

 temperate zones the weather changes in the summer 

 season are moderate, but in winter the changes occur more 

 often and cover nearly every variety of " weather," due 

 to the occurrence of numerous cyclonic storms. In the 

 frigid latitudes the changes are not quite so marked, the 

 temperature being very cold during the winter season and 

 slightly warmer during the summer. 



Weather Bureau. A large number of observing stations 

 have been established in the United States and adjacent 

 countries for the purpose of making systematic observa- 

 tions of weather conditions. At the same time each morn- 

 ing and evening at the different stations a record is made 

 of the barometric pressure, temperature, relative hu- 

 midity, the direction and velocity of the wind,- the appear- 

 ance of the sky, and the amount of rainfall. This informa- 

 tion is telegraphed to the Weather Bureau at Washington. 

 From these reports, weather maps showing the weather 

 conditions over the entire United States are printed. 

 The tabulated information is sent back to the stations in 

 the larger cities, and a smaller map is printed and mailed 

 throughout the section in which the substation is located. 

 In an almost incredibly short time the whole country has 

 been given the benefit of the information collected. 

 From the map it is quite easy for the novice to forecast 

 the weather for the next twenty-four hours, while the 

 trained observer will be able to forecast the weather for a 



