METHOD OF STUDYING MATERIAL. 235 



so applicable, and yet a similar line of thought can be 

 advantageously followed, particularly with younger chil- 

 dren. In the study of heat we can begin with its sources 

 (leading and relating finally to the ultimate source, the 

 sun), investigate next its work or function or effects 

 (from w r hich alone scientists, but not children, may gain 

 some idea of what heat is, what may perhaps be termed 

 its structure), and gradually, after many comparisons, 

 generalize or determine laws or principles, and, lastly, 

 apply these principles to the explanation of other phe- 

 nomena. The line of thought is much like that fol- 

 lowed in studying plants and animals. In work with 

 gravitation, the pressure of liquids or of air, magnetism, 

 and other physical forces or phenomena, a similar line 

 of thought can be followed. 



