NOVEMBER 93 



Holding them in this way, let them describe the 

 instrument. 



Nearest what number is the top of the column ? 



Let them put their hands about the bulb. What is 

 happening ? Nearest what number is it now ? 



Let them put the bulbs in ice-water. What is happen- 

 ing ? Nearest what number is it now ? 



What effect has heat on the column of mercury ? Cold ? 

 Why ? For what purpose is a thermometer used ? 



With a blackboard drawing, make clear to the children 

 the exact value of each of the spaces. Give them con- 

 siderable practice in reading from the board before using 

 a large thermometer. Let several children read from 

 this, holding it much below the eye, then on a level, then 

 above the eye. Put these numbers, which will probably 

 be in the ratio of 71°, 72°, 73°, on the board, and ask for 

 the explanation. 



In my own teaching, the children have always given 

 as a reason that the heated air has expanded and 

 ascended. Asked to think more about it, they came 

 the next day fortified by the assurances of their fatheus 

 and grandfathers that this is the real explanation. So 

 strong is their belief in the wisdom of themselves and 

 their families that several demonstrations of the fact 

 that the change was due to the position of the eye, and 

 not to any change in the thermometer, were necessary to 

 convince them of their error. To do this, keep the ther- 

 mometer stationary while the child, by stooping, by 

 standing erect, by standing on an elevation, sees that the 

 reading varies with his position. 



These lessons in accurate reading should be followed 

 by the examination and criticism of the results of their 

 daily inspection of the school thermometer. 



