CHAPTER VI 



FEBRUARY 



An Afternoon in February, Longfellow. 



WEATHER 



The lessons on evaporation, boiling, and condensation, 

 which have now been taken by children in all the grades, 

 should be reviewed in connection with the following 

 lessons on cloud formation, rain, snow, hail, dew, and 

 frost. 



Facts : 



The heat of the sun causes constant evaporation from 

 the surface of all water exposed to its rays. This 

 evaporated water, water vapor we may call it, is invisi- 

 ble and is lighter than- the atmosphere. Therefore it is 

 continually rising, allowing the heavier air above to come 

 down and take up more vapor. The amount of water 

 thus quietly thrown into the atmosphere is enormous. 

 In tropical countries not far from three-quarters of an 

 inch of water a day is carried off from exposed surfaces. 



Clouds : 



As this water vapor rises, it gets into colder regions, 

 and as a consequence condenses into visible masses which 

 we call clouds. Cumulus or wool-pack clouds are often 

 seen with a straight, lower edge resting on an invisible 



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