WINTER EARTH STUDY, 467 



selves ; but their interest should be centred about the ques- 

 tion, and their attention directed to what will help them to 

 answer the question. The important points are : 



First. The fact or process of evaporation, the turning 

 of water into water-dust, which we can see, and into vapor, 

 which we cannot see. 



Second. The effect of heat in causing or increasing 

 evaporation. 



Third. The effect of a large surface in increasing 

 evaporation. 



Fourth. The effect of currents or winds in increasing 

 evaporation. 



Special pains must be taken to make these clear, and to 

 " clinch " them in the summaries, oral or written. 



Preliminary study of alcohol stove. To guard against 

 or lessen the tendency to watch the apparatus rather than 

 the experiment, it is well to take a little time to study with 

 the children the stove and the way it is used. Then 

 impress the idea that they are to watch what is done and 

 what happens. 



RAPID EVAPORATION, OR BOILING. 



Step I. What does the water do ? Heat a little water 

 in a shallow dish (lid of jelly glass, or baking-powder can), 

 over alcohol stove. Direct attention and observation to the 

 water. " We want to see what happens to the water." 

 The children, even the youngest, can observe, and tell that 

 " Miss Grey put the water in a tin lid." "She put the lid 

 over the stove." "The flame went up around the dish." 

 "The water got warm." "Little bubbles came in the 

 water." Some bubbles were at the side." " Some bub- 

 bles were at the bottom." "The bubbles dance up and 

 down." " Soon the water all went away." " No water 

 was left in lid." 



