1 8 Evaporation and Condensation. 



1 6. If you should boil a kettle of salt water v 

 the vapor passing off would be fresh. This you 

 may prove by conducting the vapor through a 

 tube or pipe cold enough to condense or change 

 the vapor back again to water ; this water will 

 be fresh. 



(The teacher may now draw on the black- 

 board this picture, of a size sufficiently large to 

 be seen by the whole class ; or, the drawings 

 which enter into a certain day's lesson may be 

 previously prepared on the blackboard.) 



Drawing for the blackboard explaining evaporation and con- 

 densation; also, how fresh water maybe procured from salt 

 water, by conducting vapor through a pipe that is kept cold. 



17. If you were at sea and without drinking-water, how 

 could you obtain it ? By boiling the salt water in a kettle 

 and conducting the vapor into a cold pitcher or bowl, or 

 through a pipe kept constantly cold. What becomes of the 

 salt in the process of evaporation ? // remains behind in 

 the kettle. 



SI ELL AND DEFINE Tube, boil, salt, kettle. 



