THE ATMOSPHERE. 



49 



freezes, the moisture condensed from the air, instead of 

 forming dew, forms crystals of ice, or frost. 



When there is 110 dew, there can be no frost of this 

 kind, and vegetation is not injured unless the temper- 

 ature falls low enough, and remains low long enough to 

 freeze the sap within the plant. 



^ ^ Isobars, every fifths of an inch difference Direction of wind & clear weather 



of pressure. < t i< u tt , , u 



Isotherm*, errri/ 10 dcyrees temperature. ~ ~+ 



" Low " = Center of (' i/clone. ' ''"'" 



"///</A"-- Aiiticii<l<ies. m _ < " " "snow. 



^ V- path of Cyclone. 



Weather Map. 



The Weather. The changes of weather which are con- 

 stantly taking place are not. irregular and accidental. 

 They occur according to certain laws, and as the result 

 of certain causes. By ascertaining these causes, it is 

 possible to predict changes, so that a storm, or a cold or 

 warm wave of temperature, may be foretold some hours 

 before it appears. 

 WINS. Ao. 4. 



