82 



NATURE STUDY 



Place the flask on the stove, or over an al- 

 cohol lamp, and have the class observe the 

 result, and, if they can do so, explain why 

 the water rises. If the simple explanation 

 that the heat makes the water larger (ex- 

 pands it), is not given, do not give it but al- 

 low them more time to think on the mat- 

 ter. If wrong explanations are offered do 

 not immediately reject them, but ask for 

 proofs or devise experiments which disprove 

 the offered explanation. For example, if a 

 child insists that the water rises in the tube 

 " because heated water is lighter and goes 

 up," place the apparatus so that it extends in 

 a horizontal position, and repeat the experi- 

 ment. The above may occupy the time of 

 more than one lesson. It ought not to be 

 hurriedly passed over. In subsequent lessons 

 it may be proposed to experiment with other 

 liquids. Allow the children to select the 

 liquids, arrange the apparatus, and try the 

 experiments as far as possible. The effect of 

 cold may be studied also. 



When a few liquids are thus experimented 

 with and comparisons made between them, 

 the thermometer may be introduced. It is 

 to be seen as a small flask filled with mercury, 

 or with colored alcohol. 



A number of simple experiments can be 



Jevised with the thermometer which will make clear its use in 



determining the temperature of things. 



In all experiments give as much chance as possible for each 



Fig. 53. lixpansion of 

 water by heat. 



