WIN TEE EARTH STUDY. 487 



the ice. Invert larger jar or can over bottle and saucer, 

 as before, and heat gently over alcohol stove. Soon frost 

 will form on the surface of the bottle or can which con- 

 tains the ice and salt. Watch the process very carefully, 

 removing the inverted jar frequently. Note how the minute 

 particles of frost form ; how they grow, some pushing 

 away from the surface of the bottle, some sending out 

 arms over the bottle ; how the arms often interlace ; how 

 the frost crystals glisten; how cold they feel, and how 

 they melt, showing that they are made of water or ice. 

 If the same experiment is repeated, but without the inverted 

 jar or can, children can see that the frost forms best where 

 there is much moisture, and where it cannot scatter through 

 the air, and can explain why frost forms most quickly in 

 low places and on quiet nights. A wooden water-pail filled 

 or partly filled with a mixture of finely pounded ice and 

 salt soon becomes coated with frost. The star-like frost crys- 

 tals, resembling minute snowflakes usually form freely ; they 

 should be observed with a magnifying-glass, a reading-glass 

 if obtainable. 



Perhaps the children can tell where frost forms on the 

 windows at home, most abundantly in or near the kitchen 

 or washroom or bath-room, where there is plenty of mois- 

 ture or water dust. Why ? 



Observation of frost work. Whenever frost work on 

 windows is particularly good, stop other nature work to 

 study the frost pictures with the children. If it is pos- 

 sible to see how the frost work grows or spreads over the 

 window-panes, or to get one or two children to watch it at 

 home and tell about it, much will be gained. Try to find 

 some of the little star-like crystals (as a preparation for 

 snow study). Note how the arms or branches crowd to- 

 gether, and push out from the glass (as a preparation for 

 the study of the formation of ice). How the children 



