THE ATMOSPIIKKE. 



49 



freezes, the moisture c(jiideiised from the air, instead of 

 forming' dew, forms erystals of ice, or frost. 



When there is no dew, there can be no frost of this 

 kind, and vegetation is nt)t injured unless the temper- 

 ature falls low enough, and remains low long enough to 

 freeze the saj) within the })lant. 



^ _^Isohnrs, every ^Jhs of aninch difference 



of pressure. 



Isot/ierin.i, erery 10 degrees leinperuture, 



" Low " = Center of Cyclone. 

 "Ilif/h'''' = Aiilicytloiies. 



. Direction of wind tfr clear v:eather. 

 " " " " cloudy " 



" " " " rai-n. 



" " " " snow. 



>^. 



V- path of Cyclone. 



Weather Map. 



The Weather. — The changes of weather Avhich are con- 

 stantlv taking place are not irregular and accidental. 

 They occur according to certain laws, and as the result 

 of certain causes. B}- ascertaining those causes, it is 

 possil)le to predict changes, so that a storm, or a cold or 

 warm wave of temperature, may be foretold some hours 

 before it appears. 

 Wins. Ag. —4. 



