88 NATURE STUDY Y GRADES 



mountain? Where can snow be found all summer, even 

 in warm countries? Why? People who ascend high in 

 balloons take warm clothing with them. The temperature 

 of the City of Mexico seldom exceeds 70 degrees, while in 

 many places much farther from the equator it reaches 100 

 degrees, or higher. Why is this? 



LESSON XI 

 THE THERMOMETER 



Show the pupils a thermometer. Breathe on the bulb, 

 and let them see the mercury rise. Hang the thermometer 

 in a warm place, and note the change in the height of the 

 mercury. What makes it rise? W T hat makes it fall? Of 

 what use, then, is the thermometer? 



Let the pupils note the grading of the thermometer. Some 

 excellent number work may be done in recording and com- 

 paring temperature changes. At the proper time, take the 

 temperature of melting ice or snow and also that of boil- 

 ing water, if the instrument is made to indicate boiling 

 point. 



Teach the children to judge the temperature of the air, 

 verifying by looking at the thermometer. Let them feel of, 

 and judge, the temperature of very warm water. Test with 

 a thermometer. Reduce the temperature 20 degrees by 

 adding cold water. Let the pupils feel of it again and judge 

 its temperature, then verify by using the thermometer. Add 

 more cold water, and test as before. 



In a subsequent lesson the same work may be done, 

 lowering the temperature 10 degrees each time instead of 

 20 degrees, letting the pupils judge each time, and after- 



