CIRCULATION OF AIR IN SCHOOLROOM. 77 



greater or less than when the rubber dia- 

 phragm was pushed up into the glass 

 bell jar? 



3. What is the effect on the rubber balloon of 

 thus increasing the size of the cavity in 

 which the balloon is hung? Why? 

 C. Application to the action of human diaphragm 



and lungs. 



1. In what respects does this model illustrate 



the process of inhaling and exhaling air 

 in our own bodies? 



2. In what respects does the model fail to il- 



lustrate the process of respiration? 



39. CIRCULATION OF AIR IN SCHOOLROOM. 

 (Dem.) 



Materials: Concentrated hydrochloric acid, concentrated ammo- 

 nia; evaporating-dishes. 



Pour into an evapora ting-dish some concentrated 

 hydrochloric acid ; into another dish pour some con- 

 centrated ammonia. 

 A. Bring the two dishes near together. 



1. What is the effect? 



2. Place the two dishes near the hot-water or 



steam -pipes. Describe the course of the 

 fumes. 



3. Place the dishes near the opening to a ven- 



tilator. What course do the fumes take ? 



4. Draw a diagram of the room and indicate 



by arrows the course of the moving air 

 as demonstrated by the fumes. 



