150 NATURE STUDY. 



determining, or rather expressing, the order in which 

 the mind most readily receives and retains ideas or 

 impressions. 



Sixth. Unity, combining or merging diverse ideas into 

 one, the condition to which the mind strives to reduce 

 all ideas, and with which alone the mind is satisfied. 



Seventh. Expression, as determining the means by 

 which the child can convey his ideas to others, and at 

 the same time fix or impress these ideas in his own 

 mind, and gain power to get ideas from others. 



By what we may call the law of sense-perception, we 

 mean that the child must originally gain his ideas 

 through his senses. All entirely new matter must 

 come through his senses. 



When we attempt to give the child new ideas 

 through the artificial symbols which we call words, we 

 often violate this law, and fail in our work. This law 

 is of the greatest importance and widest application in 

 science, or nature study. True science, or nature study, 

 probably more than any other other line of work, must 

 be founded and built upon sense-perception. 



This is most essential in work in primary grades, and 

 in any grade when beginning nature study. In later 

 study, much can be founded or built upon the sense- 

 perceptions and the mental pictures gained in earlier 

 work. 



Just here special care is necessary. Unless teachers 

 take every precaution, make sure that pupils see with 

 their own eyes, instead of merely listening or absorbing, 



