AIR VITIATED. 249 



Q. Wlmj is the GALLERY of a CHURCH or 

 theatre HOTTER than the AISLE or pit ? 



A. The hot air ascends from the 

 bottom to the top of the room, and cold 

 air (from the doors and windows) flies 

 to the bottom to supply its place, 



Q. Why does a CROWDED ROOM produce 



HEAD-ACHE ? 



A. Because we breathe air vitiated 

 by the crowd. 



Q. How does a CROWD VITIATE the AIR of a 

 ROOM? 



A. Whenever we breathe, the ele- 

 ments of the air are separated in the 

 lungs, some of the oxygen is absorbed by 

 the bloody and some of it is converted 

 into carbonic acid gas, and exhaled with 

 the nitrogen. 



Q. Is ALL the NITROGEN REJECTED by the 

 lungs ? 



A. Yes; all the nitrogen of the air 

 is always exhaled. 



Q. What is CARBONIC ACID GAS ? 



A. As carbon has a very great 

 affinity for oxygen, therefore, whenever 

 they are exposed to heat, they combine. 



