WINTER EARTH STUDY. 469 



until they disappear. They at last become so small that they 

 are like the chalk dust. We cannot see one drop alone, 

 but we can see many together. So we can call them 

 what? Water dust. (Water dust is the more exact term 

 for what is popularly called " steam." Steam, correctly 

 speaking, is water vapor, and is invisible. The term " steam," 

 referring to water dust, is so generally used in the chil- 

 dren's homes that it does not seem wise to insist that the 

 children shall not use it. Tell them we like better the 

 name "water dust.") If they persist in calling water dust 

 " smoke," show them, with a match, that smoke is made 

 when things burn, and that it makes a tin or saucer black, 

 while water dust is made when water boils, and it makes 

 the tin wet. 



After having children tell, as well as they can, what they 

 did and what they saw, impress by repetition the idea 

 that: 



The fire turns the water into little drops. 



The drops get small like dust. 



Many drops together look like smoke. 



Then we call it water dust. 



Other people call it steam. 



Call attention to the fact that water dust cannot be fol- 

 lowed or seen far from the alcohol stove. It seems to " go 

 into the air." Show children how chalk dust when scat- 

 tered by blowing on it also " goes into the air." When the 

 little drops of water dust become so small and so scattered 

 that they cannot be seen we call them vapor. Impress the 

 idea: 



When water dust is so fine that we cannot see it, it is 

 called vapor. 



Now and not before the children are ready for the 

 terms " e-vapor-ate," " to turn into vapor," and " e-vapor- 

 ation," "turning into vapor." 



