12 LABORATORY LESSONS IN GENERAL SCIENCE 



people in cold weather and in cold climates crave fatty 

 foods? What is the normal temperature of the body? 



9. What are signs of lack of oxygen in the air that we 

 breathe? By what means other than respiration may the 

 air of our rooms be robbed of its oxygen? What provision 

 does nature make to rid the air of carbon dioxide and restore 

 oxygen to it ? 



VENTILATION 



1. Over two holes cut in the cover of an empty cigar box 

 set chimneys made air-tight at the bottom with vaseline. 

 Have a bit of candle burning within one of the chimneys. 

 Test for air currents at the tops of the chimneys by means 

 of smoke from an extinguished match (or joss stick). Ex- 

 plain in full what is discovered. 



What is true of the relative temperatures of the air in the 

 two chimneys? In what other respects is the air above 

 the candle unlike that in the other chimney? How was 

 the air in the box affected because of the differences in 

 temperature of the air in the two chimneys? 



2. Why does the air of a schoolroom need to be continu- 

 ously changed? At what season of the year is it neces- 

 sary to give especial attention to this matter? What eco- 

 nomic considerations are to be taken into account in the 

 ventilation of rooms in winter? What danger to health 

 must be avoided? What change should the outside air in 

 winter undergo before it is allowed to spread through an 

 occupied room ? By what means other than that employed 

 above might a current of air be maintained through the rooms 

 of a building ? 



